International Rice Research Contents Notes March 1994

The International Rice Research Notes (IRRN) expedites communication among scientists concerned with the development of improved technology for rice and rice- based systems.

to help scientists keep each other informed of current rice research findings. The concise scientific notes are meant to encourage rice scientists to communicate with one another to obtain details on the research reported.

The IRRN is published quarterly in March, June, September, and December by the International Rice Research Institute; annual subject and variety indexes are also produced.

The IRRN is divided into three sections: notes, news about research collaboration, and announcements.

The IRRN is a mechanism

Germplasm improvement

Genetic resources

China 4 Rice remains from Neolithc Age excavated in

Breeding methods 4 Effect of seedling age on flowering of

cytoplasmic male sterile and restorer lines of rice

5 Genetics of fertility restoration of wild abortive cytoplasmic male sterile lines in rice

5 Restorers for cytopiasmic male sterile lines derived from MS577 A

Yield potential 6 Stability analysis of six medium-duration rice

genotypes across different N levels 7 Relationship of amylase activity to rice seedling

growth at various greenhouse temperatures 8 Variability, heritability, correlation, path analysis,

and genetic divergence studies in upland rice

Pest resistance—diseases 10 Strain differentiation of rice tungro bacilliform

virus by restriction fragment length analysis of polymerase chain reaction-amplified products

11 Neck blast-resistant lines of Radha-17 isolated 11 Screening rice accessions for resistance to rice

tungro

Pest resistance—insects

and cultivated rices

Integrated germplasm improvement—irrigated 13 Xiang-zhong Xian No. 3: a high-yielding, widely

useful rice variety in Hunan, China 13 La Plata Mochi F. A., a new rice variety from

Argentina 13 Pant Dhan 10 replaces Pant Dhan 4 and Sarju 52

14 A high-yielding mutant line of traditional aromatic

14 Pant Dhan 11, a new rice variety for the lower

12 Resistance to whitebacked planthopper in wild

in western Uttar Pradesh, India

rice cultivar Gobindabhog

hills of Uttar Pradesh, India

Integrated germplasm improvement—rainfed

15 Vaidehi, a variety for rainfed lowland conditions lowland

in Bihar, India

Seed technology 16 Influence of alkalinity on rice germination and

growth

Crop and resource management

Soils 16 Effect of green manures on ammonia-release

17 Effect of urea application timing on ammonia pattern in rice soils

volatilization in green manure-amended wetland rice soil

Fertilizer management—inorganic sources 18 Seasonal influence on placement of urea

18 Fate of applied N in traditional, modern, and supergranules in rice

conservation farming systems of lowland rice in Sri Lanka

Integrated pest management—diseases 19 Occurrence of rice tungro disease in central

Vietnam

Integrated pest management—insects 20 Thrips affected by steam distillates of resistant

20 Sampling spiders during the rice fallow period 21 Host plant range of Pseudococcus saccharicola

22 Host plant range of leafhopper Cicadulina

23 Developmental biology and host plant range of

varieties and wild rices

Takahashi

bipunctata (Melichar)

rice ear-cutting caterpillar Mythimna separata (Walker)

Integrated pest management—weeds 24 Weed species in rice seedling nurseries in Kafr

El-Sheikh governorate, Egypt

ISSN 0115-0944

Farming systems 25 Slash-and-burn upland rice production in Bolivia's

chapare region Yield ability and net return of rice-based

regimes in Bihar, India

Research methodology

27 An improved protocol for nonradioactive DNA page 20 analysis using digoxigenin labeling

28 Nonradioactlve DNA analysis using biotin labeling and chemiluminescent detection

30 Aseptic mass collection of anthers for increasing efficiency of anther culture in rice breeding

30 Polymerase chain reaction amplification of DNA from bacterial pathogens of rice using specific oligonucleotide primers

cropping sequences under different water

News about research collaboration

32 Computers help predict how rice blast disease

32 Bangladesh and IRRI: more than 20 years of rice

33 GIS: a new tool for analyzing rice germplasm 33 SARP theme leadership shifting to NARS and

will react to climate changes

research collaboration

IRRI

policy 33 Ministry in Vietnam endorses no early spray

Announcements

34 34 34 34 35

35 35 35 36 36

Postdoctoral research fellowships at IRRI Tropical agriculture conference New IRRI publications New publication IRRI extends deadline for nominating young women scientists for 1994 award Rice dateline Call for news IRRI address IRRI group training courses for 1994 Rice literature update reprint service

Instructions for contributors

Inside back cover

page 10

page 4

26

Hemudu. Based on length, width and shape of grains, and characteristics of awns, the grains were identified as cultivated indicas and japonicas and a few types of wild rice ( O. rufipogon Griff). In Luojiajiao, the grains origi- nated from japonicas.

Many carbonated grains and hulls were discovered in unearthed pottery in Pengtoushan. Some scientists think these are grains of cultivated rice.

Based on these findings, rice farming may have been developed as long as 8,500 years ago in the middle and lower basins of the Yangtze River.

Tang Shengxiang, China National Rice Research Institute, Hangzhou 310006, China

Germplasm improvement

Rice remains from Neolithic Age excavated in China -

China is one of the first countries in which rice was farmed. One hundred nine Neolithic remains of rice culture in China, dating back to 1050-5850 BC, have been studied. Carbonated grains were most commonly excavated.

Forty-nine of the samples date to 1050-2550 BC, 43 to 2550-4050 BC, and 17 to 4050-5850 BC. Eighty-two of the remains, including the three oldest at Luojiajiao, Hemudu, and Pengtoushan, were discovered in the middle and lower basins of the Yangtze River (see figure).

Thousands of carbonated whole grains, leaves, and stems were found in

Distribution of excavated rice remains from the Neolithic Age in China.

Effect of seedling age on flowering of cytoplasmic male sterile and restorer lines of rice G. Bassi, A Rang, and D. P. Joshi, Seed Science and Technology Department, Punjab Agricultural University, Ludhiana 141004, Punjab, lndia

Nonsynchronized flowering of parental lines, unavailable area-specific seed production technology, and difficulty in arranging adequate isolation make hybrid rice seed production challenging. We manipulated seedling age of some cytoplasmic male sterile (CMS) and restorer lines (prospective parents of promising hybrids) to synchronize flowering.

Four CMS and eight restorer lines were studied during 1992 wet season. The nursery was transplanted when seedlings were 20, 25, 30, 35 ,40, and 45 d old. Data were recorded at initiation of panicle emergence, 50% flowering, and complete flowering. Days to flower- ing were calculated from transplanting date.

Seedling age affects panicle emer- gence in both CMS and restorer lines (see figure). Panicle emergence tended to be delayed in the 20- and 25-d-old seedlings but was quicker in those 35-45 d old. In general, panicle emergence was advanced or delayed by half the number of days difference in seedling age compared with a 30-d-old seedling. Data at panicle emergence correlated with those at 50% flowering and complete flowering.

In genotypes IR58025 A, IR13292 R, PAU1106-21-3 R, and PAU1106-21-4 R, panicle emergence was delayed or advanced by as many days as there was difference between seedling age and a 30-d-old-seedling. Genetic differences among genotypes in the ability of seedlings to establish after transplanting might cause this difference in panicle emergence.

4 IRRN 19:1 (March 1994)

Genetic resources Breeding methods

Genotypes

Genotypes

5-4 R

2-1 R

2-2 R 4 = lR32841 R 5 = IR31802 R 6 = 3 A 7 = 8 A 8 = 10 A 9 = IR13292 R

10 = lR58025 R 11 = PAU1106-21-

3 R 12 = PAU1106-21-

4

1 = PAU1106-21-

2 = PAU1106-47-

3 = PAU1106-47-

Effect of seedling age on panicle emergence in rice.

In Pankaj and Rajshree, Rf 1 had a stronger effect on fertility restoration than did Rf 2 . Fertility restoration was high when both dominant alleles ( Rf 1 , Rf 2 ) were present. It was less pronounced when only R f 1 was present, and was further reduced (partial fertility) when only Rf 2 , was present. The double recessive genotype ( rf 1 rf 1 rf 2 rf 2 ) did not restore fertility. Only one dominant restorer gene ( RfRf ) was found in Pusa

Variation in seed fertility restoration indicates these genes have different penetrance and are affected by modi- fiers.

Genetics of fertility restor- ation of wild abortive cyto- plasmic male sterile lines in rice P. K. Singh, R. Thakur, and V. K. Chaudhary, Plant Breeding Department, Rajendra Agricultural University, Bihar, Pusa (Samastipur) 848125, lndia

Thirteen elite rice cultivars were crossed with cytoplasmic male sterile (CMS) lines V20 A, IR54752 A, and IR58025 A. Pusa 33, IET6148, Pankaj, Rajshree, and TCA48 were identified as effective restorers based on seed and pollen fertility of the F 1 s.

Only six testcrosses had more than 90% seed and pollen fertility in F 1 . The F 2 progeny of these were analyzed for inheritance of fertility restoration (see

table). On the basis of percent seed set, F 2 plants were grouped as fertile (above 80% seed fertility), partially fertile (20-80% fertility), and sterile (below 20% seed fertility).

Rf 2 , are known in rice. Two independent dominant genes govern seed fertility restoration ability of Pankaj and Rajshree; a single dominant gene governs restoration in Pusa 33.

The mode of action of the two genes varied in the four crosses. The F 2 popula- tion of V20 A/Rajshree, IR58025 A/ Rajshree, and IR58025/Pankaj segregated into a 9-6-1 ratio, revealing epistasis with incomplete dominance. V20 A/Pankaj showed dominant epistasis (12:3:1). V20 A/Pusa 33 and IR58025 A/Pusa 33 showed monogenic segregation (see table).

Two fertility restoration genes, Rf 1 and

Segregation for fertility restoration in F 2 populations of some crosses. Cuttack Rice Research Institute, Cuttack, India, 1991 rabi season.

Cross F 1 seed F 1 F 2 Segregation for Expected fertility pollen plants seed fertility a segregation

(%) fertility (no.) ratio (%) F PF S

V20 A/Rajshree 92 93 154 92 54 8 9:6:1 0.85 V20 A/Pusa33 92 93 163 116 - 46 3:1 0.99 V20 A/Pankaj 90 91 130 94 26 10 12:3:1 0.67 lR58025 A/Rajshree 91 94 174 101 61 12 9:6:1 0.49 lR58025 A/Pusa 33 94 96 180 142 - 38 3:1 1.45

92 93 121 72 39 10 9:6:1 1.91

a = fertile (above 80% fertility), PF = partially fertile (20-80% fertility): S = sterile (below 20% fertility).

Restorers for cytoplasmic male sterile lines derived from MS577 A S. Leena Kumary, M. Mahadevappa, and A. Mohan Rao, Genetics and Plant Breeding Department, University of Agricultural Sciences, GKVK, Bangalore 560065, India

Several stable cytoplasmic male sterile (CMS) lines (Pushpa A, Mangala A, ES18 A, and Intan Mutant A) developed in Karnataka carry MS577 A cytoplasm and have good agronomic traits. They could not be used directly to develop hybrids, however, because good restorers were not available. We successfully identified effective restorers for them.

We crossed the CMS lines with improved varieties and cultures and obtained 115 F 1 s at the Main Research Station, Hebbal, during 1992 dry season. Hybrids and their parents were trans- planted during 1992 wet season in rows of 30 plants spaced at 15 × 20 cm. Ten plants from each hybrid were labeled. Three panicles from each plant were marked and then bagged before flower- ing. Spikelet fertility was calculated as percentage of filled grains.

Florets from the upper part of the panicles were collected before flowering and stained with 1% acetocarmine for pollen fertility studies. Pollens classified as fertile were fully developed, round, and stained deeply.

Individual plants were classified as fertile, partially fertile, and sterile based on pollen and spikelet fertility. Pollen

IRRN 19:1 (March 1994) 5 IR58025 A/Panka

33.

IR58025 A/Pankaj

c 2

a M = maintainer, where pollen fertility and spikelet fertility= 0%; PR = partial restorer, where pollen fertility and spikelet fertility = 1-80%; and R = restorer, where pollen fertility and spikelet fertility = 81-100%.

S. Geetha, A. P. M. Kirubakaran Soundararaj, S. Giridharan, S. Mohandas, T. M. Thiyagarajan, and B. Selvi, Tamil Nadu Rice Research lnstitute (TNRRI), Aduthurai 621001, Tamil Nadu, India

We studied the adaptiveness and stability of medium-duration rice at 0, 75, 150, and 225 kg N/ha. Genotypes ADT38, CO 45, ADT90072, Vikramarya, ADT40, and ADT39 were raised in a split-plot design with four replications from Oct 1992 to Feb 1993. N levels, applied as urea in three splits, were in the main plots. The genotypes, transplanted at a spacing of 20 × 10 cm, were in the sub- plots.

Data on panicles/plant, grains/panicle, percent fertility, 100-grain weight, single- plant yield, and harvest index were collected for 10 plants per experimental unit. We used the means of those plants for stability analysis following the method of Eberhart and Russel (1966). Pooled analysis of variance showed significant differences among genotypes and N treatments for all characters. Genotype × N interaction was also significant for all characters but 100- grain weight.

Stability analysis of six medium-duration rice genotypes across different N levels

parents were grouped into restorers, partial restorers, and maintainers (see table').

Of the 65 genotypes tested, 5 were restorers, 28 partial restorers, and 32 maintainers. Kumkum Kesari, IESH1, HWR30, CTH3 (Mukthi), and V20 B were restorers.

A pollen parent sometimes behaved as a restorer for one CMS line and as a partial restorer or maintainer for another. This shows that marked cytoplasmic nuclear interaction exists and that expression of restorer genes varies with genetic background of the female parents.

Maintainers and restorers for MS577 A CMS lines. a Karnataka, India. 1992 wet season.

Genotype CMS lines

Kumkum Kesari ARC11353 IPS15 IPS16 M102 Suweon 352 Basmati 370 Netra Nutshell Manipur

CSR107 Mandya Vani Mandya Vijaya IESH1 CTH1 HWR30

lET5657-33

Pushpa A Mangala A ES18 A lntan Mutant A

PR M R M M M PR M PR M M M M PR PR PR M M M M PR PR PR PR PR M M R R M R PR

Taichung 65 CTH 3 (Mukthi) IET8050 IET2014 HB5 IET5656 HWR2 Pusa 702 Chamundi IET7991 M210 IET7191 Milyang 54 IET8050 lndrasan Milyang 46 Primala Purple dwarf IR26 IR36 IR42 IR46 IR50

IR52 IR54 IR64 IR74 lR2429-315 lR2729-105 lR2797-105

IR50-31

lR3429-350 lR9761-19-1 lR11418-15-2 lR13146-45 lR13249-30 lR15975

lR21916 lR18350-90

M PR R M M M M M PR M M

PR

M M

M PR

PR PR M M M

M M M M

M

M M M PR M M PR

M M M M M

PR M M

PR M

M PR PR

PR M

M M

M

R

M

M

M PR

M PR M PR

PR M M M M PR PR M M M

lR25867-29 PR lR27315 M lR28178-70 M lR28237-31 PR lR30864 M M lR31358-90 PR lR35358-90 PR lR54752-3-5-8 PR M V20 B R M M

6 IRRN 19:1 (March 1994)

Yield potential

–

– – –

– – – – – – –

–

– – – –

– – – – – – – –

– – – – – –

– – – – – – –

– – – – –

– – –

– – – –

– – –

– – –

– – – – – – – – – – – – – – – –

– – – – –

– – – –

–

– – – – –

–

– –

– – – –

– – – – – –

– – – – – –

– –

– –

– –

– – –

– – – –

– – – – – – – – –

– – – – –

– – – – – – –

– – –

–

–

Table 1. Stability parameters (X, b i , and s -2 d i ) of six traits. a TNRRI, Tamil Nadu, India. 1992-93.

ADT38 CO 45 AD90072 Vikramarya ADT40 ADT39

ADT38 CO 45 AD90072 Vikramarya ADT40 ADT39

Panicles/plant Grains/panicle

X b i s -2 d i X b i s -2 d i

10.05 1.306 0.249** 41.88 0.03 4.197 8.43 0.496** 0.002 54.75 1.37 7.148* 9.08 1.106 0.485** 64.68 0.26 6.835* 7.45 0.89 0.838** 44.05 1.23 5.914*

10.46 1.27 0.126 64.23 1.73 29.27** 9.17 0.93 0.382** 68.78 1.37 22.79**

Percent fertility

X b i s -2 d i

64.39 2.92 5.67* 59.51 0.89 1.21 66.94 1.73 0.48 54.63 0.20 0.25 69.00 1.42 0.31 68.07 –0.75 9.11*

100-grain weight Single-plant yield Harvest index

X b i s -2 d i X b i s -2 d i X b i s -2 d i

1.97 2.67 0.0004** 7.74 0.55 0.063 0.40 0.66 0.00009 2.34 0.40* 0.000 9.64 0.49 0.002 0.36 1.94** 0.00003 1.97 0.61 0.0005** 10.08 1.02 0.202* 0.40 1.64 0.00004 2.60 1.03 0.0000 9.14 1.03 1.690** 0.36 1.37 0.00020* 2.25 0.49 0.000 13.29 1.76 0.645** 0.34 0.15 0.00020 1.68 0.80 0.0000 10.42 1.15 0.387** 0.49 0.25* 0.00000

a * * and * = significant at the 1 and 5% level, respectively.

Table 2. Correlation among stability parameters (X, b i , and s -2 d i ). a

X vs b i X vs s -2 d i b i vs s -2 d i

Panicles/plant 0.717 –0.603 0.096 Grains/panicle 0.379 0.701 0.684 Percent fertility 0.256 0.371 –0.204 100-grain weight –0.208 –0.388 0.475 Single-plant yield 0.880* 0.095 0.395 Harvest index –0.340 –0.702 –0.224 a * = significant at the 5% level.

ADT38 and CO 45 were adaptive and stable across all N levels for single-plant yield. Mean single-plant yield was low for ADT38 and average for CO 45. The stable yield was due to stable grains/ panicle and harvest index for ADT38 and panicles/plant and 100-grain weight for CO 45. Although the mean of ADT40 was high, its yield was unstable across the N levels (Table 1).

The correlation analysis among stability parameters revealed that genotypes with a high mean for single- plant yield are responsive to high N (Table 2). There was no significant association between the stability parameters of regression coefficient b i and deviation from regression coefficient s -2 d i . It can be inferred that these two characters are not linked and are inherited separately.

Relationship of amylase activity to rice seedling growth at various green- Lushuang 1011 and Fujiang 2 were house temperatures surface-sterilized and rinsed in sterile

stress after transplanting. Seeds of hybrids Shanyou 63 and

D-you 63 and conventional varieties

Wang Sangen, Agronomy Department, Southwest Agricultural University, Chongqing 630716, China

Amylases are key enzymes for starch catabolism during rice seed germination. Higher amylase activity in kernels should enhance seedling vigor. This is important where seedlings are raised indoors before ambient temperatures are warm enough for rice growth. Temperature needs to be controlled carefully in greenhouse nurs- eries so that seedlings can better resist

water. Seeds were then immersed in water for 2-3 d (depending on tempera- ture), incubated for a day, and sown in a nutrient solution at different greenhouse temperatures.

Seedling characters and amylase activity were determined at 7 d after sowing (Table 1). Total amylase activity in kernels and dry weight of seedlings were assayed daily. Seeds were separated from shoots and roots when measuring shoot dry weight. Extracted kernel enzyme solution was incubated with

Table 1. Effects of different temperatures on seedling characters. a

Seedling height Dry weight Total amylase

shoot (µg maltose/ Mean ± sd Mean ± sd kernel per s)

Temperature (cm) (mg/plant) Root/ activity (°C)

20 4.84 0.03 d 4.45 0.03 d 0.635 a 25

84.0 c 7.88 0.15 c 7.82 0.05 c 0.464 cd 188.4 a

30 13.97 0.23 a 10.32 0.23 a 0.406 d 179.3 ab 35 10.02 0.52 b 8.16 0.14 bc 0.481 c 121.4 bc 40 0.79 0.01 e 0.85 0.04 e

30/20 8.50 0.12 bc 8.04 0.15 bc 0.499 c 152.0 ab 30/25 9.15 0.27 bc 9.52 0.26 ab 0.509 bc 137.0 b

35 20 b 9.64 0.21 bc 10.91 0.31 a 0.554 b 165.0 ab

45.5 c

a 60 plants for each sample. Means followed by the same letter are not significantly different at the 5% level. b Change in temperature treatment.

IRRN 19:1 (March 1994) 7

-

®

Table 2. Relationship between total amylase activity in the kernel and dry matter accumulation in the rice seedling. a

Temperature (°C) Power function formulas Correlation coefficient

20 Y = 0.181 × 0.963

25 lgylgx = 0.986**

Y = 0.192 × 0.917 lgylgx = 0.989**

30 Y = 0.185 × 0.981

35 lgylgx = 0.989**

Y = 0.180 × 1.008 lgylgx = 0.978**

40 Y = 0.274 × 0.729 lgygx = 0.903**

30/20 Y = 0.193 × 0.914

30/25 lgygx = 0.913**

Y = 0.187 × 0.813

35 20 b lgylgx = 0.912**

Y = 0.182 × 0.993 lgylgx = 0.980**

a ** = significant at the 1% level. b Change in temperature treatment.

pH 5.6 citric acid buffer and starch

amylase activity and dry weight in- a spectrophotometer. dry matter accumulation (Table 1). Both acid and the reactant was measured with strongly with seedling growth, especially maltose reacted with 3,5-dinitrosalicylic 63. Amylase activity was associated stopped with 0.4 N NaOH. Solution only for Lushuang 1011 and Shanyou solution for 5 min. Amylase activity was trends. Data in the tables are therefore

tained at constants of 20, 25, 30, 35, and The greater the amylase activity of 40°C, alternated between 30/25°C and the kernel, the faster dry weight accumu- 30/20°C day/night temperature, and lates in seedlings. A power function, changed from 35°C on day 1 to 20°C Y = AX B , was used to describe the on day 7. All had a 12-h photoperiod. relationship (Table 2). It is clear from

Varieties responded differently to the functions that during the young temperatures, but all showed similar seedling period, a higher shoot weight

Greenhouse temperatures were main- creased with time.

can be obtained by increasing amylase activity of the kernel.

Among the constant temperature treatments, 30°C was clearly optimum for seedling growth and amylase activity (Table 1). The aim, however, was to transplant seedlings into the field. The temperature difference between green- house and field was too great for seed- lings to adapt to the cold temperatures of early spring in southern China. The 20°C treatment was most like the ambient temperature, but seedlings were too short to transplant.

combined with high root-shoot ratio and high amylase activity, was obtained with the change in temperature treatment, which provides warmth for maximum germination and early growth. This is followed by a gradual hardening-off, which seedlings need if they are to adapt to cold temperatures. We recommend this treatment to produce vigorous seedlings that are adapted to field temperatures at transplanting.

The greatest shoot dry weight,

Variability, heritability, correlation, path analysis, and genetic divergence studies in upland rice S. S. Mehetre, C. R. Mahajan, P. A. Patil, S. K. Lad, and P. M. Dhumal, Botany Section, College of Agriculture, Kolhapur 416004, Maharashtra, India

We studied the genotypic and pheno- typic coefficients of variation, heritabil- ity, genetic advancement (GA), coeffi- cients of correlation, path analysis, and genetic divergence of 37 promising upland rice cultivars. The experiment was laid out in a randomized block design during 1992 with two replica- tions.

Analysis of variance showed signifi- cant differences among genotypes for all characters (Table 1). Considerable range of variation was expressed for plant height, panicles/m 2 , straw yield/m 2 , grain yield/m 2 , and filled grains/panicle, indicating better scope for genetic improvement in these characters. Grain yield/m 2 had maximum genotypic

coefficient of variation (GCV) (38.2), followed by straw yield/m 2 (37.6).

45.9% for plant height to 96.2% for days to maturity. Even though days to 50% flowering (93.9%) and filled grains/ panicle (85.3%) had high heritability, they had low GCV. This might be due to the variation in environmental compo- nents involved with these traits.

Expected GA ranged from 9.0% for panicle length to 73.8% for straw yield/ m 2 . Filled grains/panicle, productive tillers/m 2 , and plant height showed high GA with high GCV and should be considered for obtaining high genetic gain.

Grain yield/m 2 was positively and significantly correlated with straw yield/ m 2 ( r = 0.604) and filled grains/panicle ( r = 0.434), while it was negatively and significantly correlated with days to 50% flowering ( r = -0.495) and maturity ( r = -0.405). Plant height was signifi- cantly and positively correlated with straw yield/m 2 ( r = 0.714), panicle length ( r = 0.632) and filled grains/

Estimates of heritability ranged from

8 IRRN 19:1 (March 1994)

panicle ( r = 0.355), while it was signifi- cantly and negatively correlated with productive tillers/m 2 ( r = -0.441).

Panicle length was significantly and positively correlated with straw yield/m 2

( r = 0.547) and filled grains/panicle ( r = 0.425). Filled grains/panicle was significantly and positively correlated with straw yield/m 2 ( r = 0.647) and grain yield/m 2 ( r = 0.434).

Path analysis studies indicated filled grains/panicle extend direct positive influence on grain yield (0.077). This high magnitude of association between the two was because of the positive indirect effect through days to maturity (0.695) and productive tillers/m 2 (0.114).

Correlation and path analysis studies revealed that filled grains/panicle, plant height, and panicle length were important yield-contributing characters. They should be considered when adopting selection criteria in upland rice breeding programs.

Genetic divergence studies using D 2

analysis showed that the genotypes fall into seven distinct clusters (Table 2).

g g g

g g

g g g

Table 1. Genetic parameters of variation in upland rice. Kolhapur, Maharashtra, India, 1992.

Parameter

Characters

Days to Days to Plant Panicle Productive Filled Straw Grain

flowering (cm) (cm) (no.) (no.) (g) (g) 50% maturity height length tillers/m 2 grains/panicle yield/m 2 yield/m 2

Mean CV Range Minimum

Maximum Variance (G)

(P) Coefficient of (G)

variance (P) Heritability (%) Genetic advancement

(% of mean)

95.7 1.5

85.0 106.5

31.5 33.6

5.9 6.1

93.9 11.7

124.9 1.2

111.0 137.0

38.1 39.6

4.9 5.0

96.2 10.0

73.9 14.6 57.2

106.6 98.3

214.0 13.4 19.8 45.9 18.7

17.4 3.5

16.5 19.5

0.8 1.2 5.2 6.3

69.3 9.0

297.9 10.5

242.5 432.5

1378.5 2350.4

12.5 16.3 58.7 19.7

71.8 8.3

38.4 97.8

205.7 241.1

20.0 21.6 85.3 38.0

93.8 11.9 40.0

195.0 1244.1 1368.2

37.6 39.4 90.9 73.8

60.4 14.4 20.0

112.5 532.0 607.7

38.2 40.8 87.5 73.6

Coefficients of correlation and path analysis a

Days to 50% flowering r g b 0.964** –0.607* –0.269 0.224 –0.298 –0.361* –0.495**

Days to maturity r g –0.467** –0.210 0.101 –0.245 –0.218 –0.405**

Plant height (cm) r g 0.632** –0.441** 0.355* 0.714** 0.310

Panicle length (cm) r g –0.168 0.425** 0.547** 0.281

Productive tillers/m2 r g 0.320 –0.071 0.180

Filled grains/panicle r g 0.647** 0.434**

Straw yield/m2 (g) r g 0.604**

p c –2.332 1.525 0.501 –0.072 0.074 –0.072 –0.264

p 1.581 –2.248 0.385 –0.056 0.034 0.060 –0.159

p –0.824 1.416 –0.738 0.169 –0.147 –0.086 0.521

p 0.267 0.626 –0.333 –0.521 –0.056 –0.103 0.400

(no.) p 0.332 –0.523 0.160 0.364 –0.045 –0.056 –0.052

(no.) p –0.243 0.695 –0.388 –0.293 0.114 0.077 0.472

p 0.730 0.842 –0.345 –0.588 0.146 –0.024 –0.157

a Residual effect = 0.2709; underlined figures denote direct effects. * and ** = significant at the 5 and 1% level, respectiveIy. b r g = genotypic correlation coefficient. c p = path coefficient,

Table 2. Genetic divergence a in 37 genotypes of upland rice. Kolhapur, Maharashtra, India, 1992.

Days to Plant Cluster Genotype Areas of cultivation height

50% Maturity (cm)

I II III flowering

I ACK83-9-1, PBNR87-6, Maharashtra 102.35 131.35 63.31 BG380-2, VDN4288, (Kolhapur, Pune), RTN711, R24, Jaya Marathwada (Parbhani), RP4-14, IET6724 Konkan (Ratnagiri),

Andhra Pradesh (7.95) (10.90) (14.26)

Panicle Filled Productive Straw Grain length grains/ tillers/ yield/ yield/ (cm) panicle plant plant plant

(no.) (no.) (g) (g) IV V VI VI I

16.80 68.62 9.50 6.66 11.04

(20.34) (8.80) (14.80) (21.50) -

II PBNR87-8, PBNR87-9, Marathwada (Parbhani), 95.66 125.00 63.40 16.86 57.35 9.03 6.87 8.83 IR36, Pusa 33, K184, Western Maharashtra PLG39-4-1, Rasi, Ratna, (Kolhapur), Konkan RDN185-2 (Ratnagiri), Uttar Pradesh, - (6.94) (11.67) (15.95) (8.67) (17.35) (14.34) -

Orissa, the Philippines

III PBNR5, PBNR88-1, Marathwada (Parbhani, 91.85 121.85 86.75 17.89 80.06 7.98 11.16 10.16 PBNR88-2, PBNR88-3, Tuljapur), Western PBNR89-2, PBNR89-4, Maharashtra (Jalgaon) TP9-3-2, MAU, Prabhvati, (8.22) (12.60) (10.37) (14.29) (13.57) - Ambemohor local, Terna, Tuljapur 1, Jalgaon 5

continued on next page

IRRN 19:1 (March 1994) 9

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Table 2 continued

Days to Plant Panicle Filled Productive Straw Grain Cluster Genotype Areas of cultivation height length grains/ tillers/ yield/ yield/

50% Maturity (cm) (cm) panicle plant flowering (no.) (no.)

I II Ill IV V VI VII

IV PBNR89-6, K35-3 Marathwada (Parbhani), 86.00 Konkan (Ratnagiri)

V PBNR88-4 Marathwada (Parbhani) 98.50

VI Krishna Sal

VII Ambika

Pooled mean

Western Maharashtra 101.00 (Ahmednager)

Marathwada 85.00 (Parbhani)

94.34

112.50 77.75 18.20 (5.56)

127.00 71.40 19.50

130.00 93.40 18.70

113.00 83.50 16.50

123.90 77.67 17.78

80.70 (15.25)

86.50 (0.00)

88.40

52.50

74.76

9.08 (23.55)

7.59 (14.21)

10.08 (0.00)

58.41

8.80

9.11 18.68 (8.16) -

5.36 9.30 (17.71) -

9.90 22.87 (25.02) -

12.15 12.22 (0.00) -

8.74 13.96

a Figures in parentheses are intercluster D values. Underlined figures in parentheses are intracluster D values. Figures without parentheses are mean performance values.

When planning hybridization programs to for panicle length, Cluster VI (Krishna for straw yield/plant, Cluster VII achieve early flowering and maturity, Sal); for filled grains/panicle, Cluster. VI (Ambika). varieties from Cluster VII (Ambika) may (Krishna Sal); for productive tillers/plant, be used; for dwarfness, Clusters I and VI; Cluster IV (PBNR89-6 and K35-3): and

Strain differentiation of rice tungro bacilliform virus by restriction fragment length analysis of polymerase chain reaction-amplified products A. C. Dolores-Talens, J. R. Escara-Wilke, P. O. Cabauatan, R. J. Nelson, and H. Koganezawa, IRRI

Tungro is the most important disease of rice in South and Southeast Asia. A composite of two viruses, rice tungro bacilliform virus (RTBV) and rice tungro spherical virus (RTSV), causes the disease. Multiple strains of RTBV, a double-stranded DNA virus, have been reported recently. Each of the strains, L, G1 , G2, and Ic, manifests distinct symptoms on rice cultivars FK135 and Taichung Native 1. Strain Ic induced interveinal chlorosis, stunting, reduced tillering, and narrowing of leaves. G1 and G2 induced only mild stunting. The symptoms caused by these strains were not as severe as those manifested by type strain L.

Polymerase chain reaction (PCR) and subsequent restriction enzyme digestion were used to investigate molecular variations among the strains. Specific segments of the viral genome were amplified by PCR using oligonucleotide primers designed on the basis of pub- lished sequence data for RTBV.

intergenic region of the virus with the left, or sense strand, primer

The amplified region spanned the

(5'-TTACAGAAGGATTGTGAACCC-

3') located within open reading frame 2 (ORF2) and the right, or antisense strand, primer

3') located within ORF4 (Fig. I). Using these primers, a 2.4-kb fragment of RTBV DNA was amplified. Standard PCR conditions were used with 1-10 ng total genomic DNA extract of rice plant tissue and 50 pM primers. The amplified products were resolved on a 2% agarose gel and visualized by staining with

1. Map of the RTBV genome, indicating loca- tion of primers used and frag- ment amplified. (ORF = open reading frame, P = protein.)

(5'-ACTATAGCTCCTGCTGAACTA-

10 IRRN 19:1 (March 1994)

plant plant (g) (g)

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- - - -

- - - - -

- - - - -

Pest resistance—diseases

susceptible variety and by four rows of Sesbania aculeata, which were planted 2 and 4 wk before Radha-17. respectively. The seedbed was inoculated uniformly with 1-yr-old Bl-infected rice leaf debris.

Twenty-five-day-old seedlings were transplanted in 1-m rows at 20- × 20-cm spacing in a field fertilized with 120 kg N/ha and 26.4 kg P/ha. The experiment was inoculated twice at tillering and panicle initiation stages by uniformly spreading chopped pieces of fresh Bl- infected leaves. Disease rating was scored at maturity using the Standard evaluation system for rice (SES).

Only 60 of the 100 lines were selected as resistant in 1991. Seeds from these lines were sown in 1992 in single rows with Bl-susceptible variety Masuli in alternate rows at 10-cm spacing. All other activities were the same as in 1991.

While Masuli was severely affected by leaf Bl at the seedling stage, leaf Bl scores in all test lines were less than three on the SES scale. Neck Bl scores were 0-5 in 1991 and 0-7 in 1992; 37 lines

B. Chaudhary, National Maize Research Program (NMRP), Agricultural Research Station (ARS), Rampur; P. B. Karki, National Grain Legume Research Program, Rampur; and K, K, Lal, NMRP, ARS, Rampur, Nepal

2. (a) The

product of amplifica- tion using PCR from four RTBV strains. (b) The restriction digestion profiles of the 2.4-kb PCR product for the four virus strains using Accl, Alul, and Eco RI.

2.4-kb

ethidium bromide and viewing under ultraviolet light (Fig. 2).

were from the virus being studied, Southern blotting was performed using a labeled DNA probe of the 2.4-kb amplified fragment of the reference strain of RTBV and the labeled DNA of the entire reference strain of the virus (data not shown).

Agarose gel electrophoresis did not distinguish the PCR fragments ampli- fied from the four strains (Fig. 2a). Upon digestion with Acc I, Alu I, and Eco RI, however, variations among the strains were evident (Fig. 2b). Three DNA banding patterns were observed with each of the enzymes used. Strains G2 and Ic could not be differentiated by this method.

This information on molecular variation among the four RTBV strains can be used for diagnosis of virus strains. Further studies are needed to determine the molecular basis of the distinct symptoms incited by each strain.

To confirm that amplified products

Neck blast-resistant lines of Radha-17 isolated

were rated as moderately to highly resistant. The other 23 showed suscep- tible reactions in 1992.

These results suggest that line Radha- 17 is not pure with respect to Bl re-

similar lines might yield Bl-resistant sistance. Selection within populations of

materials. Rice blast (Bl), caused by Pyricularia oryzae Cav., is one of the most serious rice diseases in Nepal. Blast can reduce yields by 50% in areas where Masuli, Nepal’s most popular variety, is grown.

Masuli and Mallika were crossed to develop Radha-17, which has a yield potential of 4 t/ha and resists leaf Bl. Radha- 17 was reported to be susceptible to neck Bl, another serious disease. We have been working to purify neck Bl- resistant lines of Radha-17.

We selected 100 disease-free panicles of Radha-17 grown in farmers’ field trials in 1990. Seeds from these panicles were sown at 10-cm spacing in 1-m rows (panicle to row) in 1991. The trial plot was surrounded by two rows of a Bl-

Screening rice accessions for resistance to rice tungro N. Subrarnanian, R. Saroja, A. Thyagarajan, K. Nilakantapillai, and M. Subramanian, Rice Research Station (RRS), Tamil Nadu Agricultural University, Tirur 602025, Chengalpattu-MGR District, lndia

A severe outbreak of rice tungro (RTD) disease occurred on susceptible varieties ADT36, TKM9, CO 37, IR64, ASD16, and ASD18 in Chengalpattu-MGR District during 1992 sornavari season (Apr/May-Aug/Sep). Disease incidence was 60-85% at RRS. Light trap catches and in situ counts revealed that the vector, green leafhopper (GLH)

IRRN 19:1 (March 1994) 11

Table 1. Incidence of GLH at RRS, Tirur, India. Jul-Sep 1992. a

Incidence

Light trap Field Week

(no.) (no./25 sweeps)

3 Jul 436 10 10 Jul 1157 30 17 Jul 535 40 24 Jul 1794 110* 31 Jul 1354 330*

7 Aug 7064 920* 14 Aug 86234 150* 21 Aug 13091 40 28 Aug 1192 45

4 Sep 739 15

a * = above economic threshold level of 60 GLH/ 25 sweeps.

( Nephotettix virescens ), was prevalent from Jul to Aug 1992 (Table 1).

Eighty rice entries (69 cultures) and 11 varieties from the 1992 International Irrigated Rice Yield Nursery (early), Advanced Yield Trial (mid-early), and Multilocation Trial III along with susceptible check TN1 were planted in 5-m 2 plots during the second week of Jul 1992. Plants were infected with RTD at tillering, stem elongation, and booting stages. Reactions varied. Each entry was scored for RTD 45 d after transplanting using the methodology from the 1991 International Rice Tungro Nursery.

The entries and check were screened for their reaction to GLH under screenhouse conditions using the seedbox test. Seedlings were infested with five 2d- and 3d-instar GLH nymphs 7 d after seeding. Entries were scored using the Standard evaluation system for rice when 90% of TN1 plants were dead.

None of the entries were resistant to RTD. Twenty-five were moderately resistant (Table 2), 27 moderately susceptible, 19 susceptible, and 9 highly susceptible.

Table 2. Rice cultures moderately resistant to RTD. RRS, Tirur, India.

GLH RTD RTD Entry Parentage score a (%) score b

IET12888 BR51/KAU2335-2 1 1.7 2 IET12461 IR36/KJT35-3 1 2.2 2 IET12419 IR36/Jothi 1 2.6 2

IET12488 Ratna/lR36 3 3.2 2 IET12928 IR50/P338 3 4.3 2 IET12867 Palman 579/IR54 3 4.4 2 IET12355 IR50/IR36 3 5.1 3 TNRH6 IR628294/Pusa/50R 3 5.9 3 IET12914 IR50/P33/IR50/Ratna 3 6.3 3 IET12351 IR50/IET7918 3 6.5 3 TNRH1 lR628294/IR10198-66-2 R 3 7.1 3

lR59606-119-3 lR44592-62/IR20289-94 1 2.7 2

lR56382-17-3-2 lR28239-94/IR24632-34 5 7.5 3 lR58099-41-2-3 lR35366-90/IR324-29-47 5 7.5 3 lR57301-195-3-3 lR35293-125/IR32429-47 5 7.5 3 IR50 lR2153/IR28//IR36 5 7.6

IET12428 IET5233/IR2153-26 5 8.8 3

IET12929 KAU8759 5 9.0 3

IET12891 Ratna/lR36 5 9.6 3 IET12402 Govind/Ranikajar 5 9.7 3

RP1451-92-21-9 Rasi/Finegora 5 8.2 3

BG850-2 BG380/BG367-4 5 8.9 3

lR57311-95-2-3 lR39268-57/IR32429//lR42005-47 5 9.1 3

lR29725-117-2-3-3 lR19661-131/IR9125-209 5 9.8 3 lR53292-159-1-2-3 lR4563-52/IR31802-48 5 10.0 3 TN1 (susceptible check) - 9 95.0 9

a Scored using 1-9 scale in SES. b Scored using the methodology from the 1991 International Rice Tungro Nursery.

Resistance to whitebacked planthopper in wild and

We evaluated wild rice species Oryza

cultivated rices and genetically diverse rice varieties N22 officinalis, O. punctata, and O. latifolia

(Wbph l), ARC10239 (Wbph l), Ptb33 R. Velusamy, M. Ganesh Kumar, and Y. S. (Wbph 3), Podwi A8 (Wbph 4), N’diang Johnson Thangaraj Edward, Agricultural Entomology Department, Tamil Nadu Marie (Wbph 5), IR2035-117-3 (Wbph 1 Agrlcultural University (TNAU), Coimbatore + Wbph 2), and Chaia Anaser (Wbph 1 + 641003, lndia Wbph 3) for resistance to the white-

Damage ratings of selected wild and cultivated rices after infestation by WBPH nymphs in free-choice test. a TNAU, Coimbatore, India.

IRRI Damage rating (d after infestation)

number 7 11 15 Species/variety accession

O. officinalis 101114 1.0 c 1.0 e 1.0 d O. punctata 101439 1.0 c 1.0 e 1.4 d O. latifolia 100963 1.0 c 1.0 e 1.0 d O. sativa

N22 4819 1.0 c 5.4 b 9.0 a ARC10239 20803 1.0 c 3.4 c 9.0 a Ptb33 19325 1.0 c 2.2 d 7.0 c Podwi A8 15201 2.6 b 6.2 b 9.0 a N'diang Marie 15859 1.0 c 3.4 c 8.2 b

Chaia Anaser 16197 1.0 c 3.0 cd 7.8 bc TN1 8.6 a 9.0 a 9.0 a

a ln a column, means followed by the same letter are not significantly different at the 5% level by DMRT. Av of 5 replications

lR2035-117-3 1.0 c 2.6 cde 7.4 bc

12 IRRN 19:1 (March 1994)

-

Xiang-zhong Xian No. 3

Shan You 63 (check)

1990 1991 1990 1991

8.9

10.0

128 130 138 139

8.5

10.8

8.3 8.2

10.0 11.2

Performance of Xiang-zhong Xian No. 3 in 1990 and 1991 regional trials. Hunan, China.

Av grain yield (t/ha)

Highest grain yield (t/ha)

Growth duration (d)

Pant Dhan 10 (IR9763-11-2-2-3) was developed using the pedigree method following hybridization of IR32/Mahsuri/ IR28 at IRRI, Philippines. It was evaluated as IET8616 in the All India Coordinated Trials.

It is a 92-cm semidwarf that matures in 125 d. It is suitable for transplanting in

the irrigated fields of Meerut, Agra, Moradabad, and Bareilly divisions and the tarai region of Nainital District of western UP.

Pant Dhan 10 outyielded Pant Dhan 4 by 11.2% and Sarju 52 by 8.6% in the 1988-91 Standard Varietal Trials (medium) at the Regional Agricultural Testing and Demonstration Centers at Meerut, Mathura, Bareilly, and Haldwani (Table 1).

Pant Dhan 10 showed moderately resistant reaction to bacterial blight and moderately resistant reaction to sheath blight and leaf blast across several locations. Pant Dhan 10 was field resistant to stern borer, leaffolder, whorl

backed planthopper (WBPH) Sogatella furcifera (Horvath) using the seedbox screening technique.

Seeds were sown in 40-cm rows, about 2-3 cm apart, in wooden trays (60 × 45 × 10 cm) in a greenhouse. TNl was the susceptible check. The experiment was laid out in a randomized complete block design, with five replications of

each wild species and variety. Seven days after sowing, seedlings were thinned to 15 per row and infested with 6-8 2d- instar WBPH nymphs per seedling. Plant damage was scored on a 0-9 scale at 7, 11, and 15 d after infestation (DAI).

The test entries exhibited resistance at 7 DAI. Mean damage ranged from 1 to 2.6, with TN1 rating 8.6 (see table). At

11 DAI, the wild rices rated 1, the cultivated varieties ranged from 2.2 to 6.2, and TN1, 9. At 15 DAI, the wild rices had maintained their extremely high level of resistance; the varieties exhibited moderately susceptible to susceptible reactions (see table).

Xiang-zhong Xian No. 3: a high-yielding, widely useful rice variety in Hunan, China Li Yong-Chao and Li Xiao-Xiang, Hunan Academy of Agricultural Sciences, Changsha, Hunan, China

Xiang-zhong Xian No. 3 is derived from the cross Xiang-zhao Xian No. l///Ai- Bao//IR36/Shuang-Gui 36. It is a high- yielding, widely useful indica variety with multiple resistance. It was released in Jan 1992.

whitebacked planthopper, brown Xiang-zhong Xian No. 3 is resistant to

planthopper, rice blast, and lodging. It responds well to high fertilizer levels.

Xiang-zhong Xian No. 3 performed well in monocropped midseason rice areas during 1990-91 regional trials in Hunan Province (see table). It also does well as a monocropped or dual-cropped, late-season variety. Average grain yield is 7.5 t/ha.

An additional advantage is its very good ratooning ability. The average ratoon crop had a 60-65 d growth duration and yield of 5.0 t/ha from 1989 to 1991 at the Agricultural Research Institute of Changde, Hunan Province.

La Plata Mochi F. A., a new rice variety from Argentina A. A. Vidal, Estacion Experimental "lng. Agr.

Agrarias y Forestales, Universidad Nacional Julio Hirschhorn," Facultad de Ciencias

de La Plata, Buenos Aires, Argentina

La Plata Mochi F. A. is the first Argen- tine waxy rice cultivar released from the rice program of the Faculty of Agrarian and Forestry Sciences of the National University of La Plata. It was developed to satisfy the demands of Koreans and Japanese in South America.

Pant Dhan 10 replaces Pant Dhan 4 and Sarju 52 in western Uttar Pradesh, India M. P. Pandey, S. C. Mani, H Singh, J. P. Singh, S. Singh, and D. Singh, Plant

of Agriculture and Technology, Pantnagar Breeding Department, G. B. Pant University

263145, Uttar Pradesh (UP), India

La Plata Mochi F. A. is 100 cm tall, resists lodging, and grows vigorously. It has a 125-d growth duration and yields about 5 t/ha. The panicle is 2.1-cm-long. Grain shattering is minimal and thresh- ability intermediate.

The caryopsis is 5.7 cm long and 3.4 cm wide, with length-width ratio of 1.7. The waxy endosperm has 1.8% amylose content, gelatinization temperature of 6.0, alkali spreading value of 1.7, and 8.5% protein content.

Table 1. Mean performance of Pant Dhan 10 at 4 locations in western UP, India. 1988-91.

Mean yield (t/ha) % increase/decrease over Year

Pant Dhan 10 Pant Dhan 4 (check) Sarju 52 (check) Pant Dhan 4 Sarju 52

1988 5.3 4.1 4.8 +29.2 1989

+10.4 4.8 4.6 4.2 +4.3

1990 +14.2

3.9 4.1 3.7 –5.1 1991 5.5

+5.4 4.6 5.3 +19.5

Mean 4.9 +3.8

4.4 4.5 +11.6 +6.7

IRRN 19:1 (March 1994) 13

Integrated germplasm improvement—irrigated

Table 2. Distinguishing morphological characters of Pant Dhan 10.

Character Description

Height 92 cm Seedling vigor Good Lodging Resistant Plant type Semidwarf, ideal Leaf sheath Green Tillering High (15-20

Flag leaf Erect, narrow, short Photoperiod sensitivity Insensitive Panicle length 22.5 cm Apiculus color Green Awning Awnless 1,000-grain wt 26 g Grain type Long, slender Kernel length 6.9 mm Kernel breadth 2.2 mm

tillers/plant)

yielded an average of 4.6 t/ha, slightly borer, brown planthopper, blast, and more than the 4.5 t/ha of check Pusa sheath rot. It also resisted bacterial blight Basmati. It ranked fifth out of 17 entries at the IA Farm. for yield performance. The line yielded an The short, bold, white kernels are 3.7 average of 4.3 t/ha compared with 3.2 t/ha mm long and 1.9 mm wide, with a L-B for Gobindabhog in 4 yr of replicated yield

10.7 g, and the original aroma remains. trials at the IA Farm. Three farmers who ratio of 2.0. The 1,000-grain weight is

grew IET13541 (124-17-4) reported yields Alkali spreading value is 2.3 and amylose of more than 4 t/ha. content, 23.4%. The grain elongates up to

The line is about 135 cm tall, 20 cm 6.3 mm after cooking. Yields of hulled, shorter than its parent. It has erect, broad, milled, and head rice are 78.5, 73.5, and dark green leaves and compact tillers and 54.5%, respectively. The high yield panicles. It is photoperiod-sensitive, potential of IET13541(124-17-4) is matures in 155 d, and tolerates 70 kg N/ha. because it has more grains/panicle than

showed resistance to gall midge, stem In national screening nurseries, it its parent.

L-B ratio 3.1 Head rice recovery 63%

variety for the lower hills of and moderately resistant to bacterial Abdominal white Absent Pant Dhan 11, a new rice Pant Dhan 11 is resistant to leaf blast

blight under epiphytotic conditions. It has shown a moderately resistant reaction to

maggot, whitebacked planthopper, M. P. Pandey, S. C. Mani, H. Singh, J. P. brown planthopper in glasshouse screen-

screening nursery. (See Table 2 for morphological characteristics of Pant Dhan 10.)

Uttar Pradesh, India

cutworm, and gundhi bug in the national ing. (See Table 2 for morphological Singh, S. Singh, and D. Singh, Plant Breeding Department, G. B. Pant Univer- sity of Agriculture and Technology,

characteristics of Pant Dhan 11.)

Pantnagar 263145, Uttar Pradesh (UP), of Pant Dhan 11. India Table 2. Distinguishing morphological characters

A high-yielding mutant line of traditional aromatic rice cultivar Gobindabhog S. C. Ghosh and P. K. Ganguli, lnstitute of Agriculture (IA), Visva-Bharati, Sriniketan 731236, West Bengal, lndia

Gobindabhog is a popular traditional aromatic cultivar of West Bengal, India. It has small fine grain and low yield potential. Modem nonscented cultivars are not a replacement for it. Demand is high for Gobindabhog in the domestic market, and farmers get a premium for producing it. Increasing the yield of this variety would be rewarding for them.

Department of Atomic Energy, Govern- In a research project sponsored by the

Pant Dhan 11 (UPR 653-6-1-1-2) was Character Description developed by pedigree method after hybridization from the F 2 seed of Height 90 cm

IR17251 (VL 206/Dagi). It is a semi- dwarf that matures in 118-125 d, depending upon elevation. It is suitable Leaf sheath color Green for transplanting in hills up to 900 m in Tillering Medium (10-12 tillers/

elevation in UP. plant) Flag leaf Erect Photoperiod sensitivity Insensitive

better than national check Himdhan and local checks in the All India Coordi- Awning Awnless to tip-awned nated Varietal Trials (Table 1). In Grains/panicle 90-100 farmers’ field demonstrations in Kernel length 6.5 mm

Kumaon and Garhwal divisions of UP, Kernel breadth 2.7 mm

Pant Dhan 11 yielded a mean of 4.7 t/ha L-B ratio 2.95 Grain type Long, bold

compared with 4.4 t/ha for Pant Dhan 6 Head rice recovery 52% and 3.5 t/ha for local varieties. Abdominal white Absent

Table 1. Mean performance of Pant Dhan 11 in national trials in the hills of UP, India. 1985-87.

Seedling vigor Good Lodging Resistant Plant type Semidwarf, compact

Pant Dhan 11 yielded consistently

ment of India, a high-yielding mutant line (124-17-4) was created through irradia- tion by using a 25-kr dose of gamma

Trial a

rays.

Mean yield (t/ha) % increase over Year

Pant Dhan 11 Himdhan (check) Local variety (check) Himdhan Local Variety ~~

Mutant line IET13541(124-17-4) was PVT-2 (H) 1985 4.2 3.9 3.9 7.6 7.6

Mean 3.5 2.7 2.8 25.9 21.4

2.3 1.3 1.1 76.9 109.1 tested in the Initial Basmati Varietal Trial and the All India Coordinated Rice

PVT-2 (H) 1986

Improvement Program across 11 loca- a PVT-2 (H) = preliminary variety trial-2 (hills). UVT-2 (H) = uniform variety trial-2 (hills). tions during 1992 wet season. The line

UVT-2 (H) 1987 3.9 2.8 3.5 39.2 11.4

14 IRRN 19:1 (March 1994)

Apiculus color Green

Vaidehi, a variety for rainfed Table 1. Performance of TCA48 and checks Mahsuri and Br. 8 in state multilocational varietal trials

lowland conditions in Bihar, India

in 20 environments. 1986-92.

Yield (t/ha) Year Site LSD (5%) CV (%)

TCA48 Mahsuri Br. 8 R. Thakur, S. P. Sahu, A. K. Singh, R. S. Singh, and N. K. Singh, Ralendra Agricultural 1986 Patna University, Bihar, Pusa, Samastipur 848125, India

3.0 2.7 2.2 0.5 10.0 Pusa 3.1 2.9 1.9 0.6 12.6 Sabour 2.9 3.0 3.0 0.7 14.4

Nearly 2.2 million ha of rainfed lowland 1987 Patna 1.8 1.9 1.4 0.8 24.0 rice is grown in Bihar during kharif Sabour 3.8 3.4 2.6 0.6 16.8 (monsoon) season from Jun to Dec. Late Bikramganj 2.6 4.1 2.2 0.4 9.0 onset of the monsoon can delay trans- planting. The crop may also experience flooding or drought at various growth stages. Traditional cultivars are dominant in Bihar because of their superior adaptation to abiotic stresses, including low temperature at flowering. Especially in dry years, they are susceptible to bacterial blight (BB) and brown spot (BS).

We collected diverse germplasm and evaluated it in state multilocational variety trials for 7 yr to identify a suitable cultivar for release. On average, cultivar TCA48 outperformed check cultivars Mahsuri and Br. 8 in 20 environments (Table 1). When tested in Indian Council of Agricultural Research (ICAR) - IRRI Collaborative Lowland Consortium Trials in eastern India during 1992, TCA48 significantly outyielded local checks under normal and delayed transplanting (Table 2). TCA48 was resistant to BS, BB, and sheath rot (ShR). In pest complex reaction trials at Pusa, TCA48 yields declined by only 5.0% in 1991-92 and 8.7% in 1992-93 relative to protected checks.

TCA48 was released as Vaidehi in 1993. Vaidehi is a photoperiod-sensitive variety with sturdy stems, dark green foliage, and long panicles. It is 140- 150 cm tall. Grain is long and bold; the kernel is faintly red.

Vaidehi should be a stable performer in the presence of BS, ShR, and BB, and across a range of transplanting times and problem lowland and shallow deepwater conditions.

1988 Patna Sabour Bikramganj

1989 Patna Pusa Sabour Bikramganj

1990 Pusa Sabour

1991 Patna Sabour

1992 Patna Pusa Sabour

Pooled mean Pooled LSD (0.05)

3.8 3.3 4.4

4.1 3.2 2.7 3.6

3.1 3.0

2.9 2.1

4.0 1.0 2.2

3.0 0.6

3.7 3.2 3.8

2.0 2.0 2.6 3.6

2.3 2.6

2.8 2.7

2.5 0.2 2.5

2.7 0.6

2.4 2.0 2.7

1.9 2.3 2.6 2.5

2.2 2.6

2.5 3.0

3.4 0.5 2.2

2.3 0.4

1.0 0.5 0.7

0.8 1.2 0.4 0.7

0.7 0.5

1.2 0.2

1.0 0.6 0.4

0.7

16.4 14.2 10.6

20.7 9.8 8.6

14.8

20.0 10.3

23.0 5.5

18.5 46.5 12.8

Table 2. Performance of TCA48 in different sites in eastern India under ICAR-IRRI Collaborative Lowland Consortium Trials. 1992 kharif.

Yield (t/ha)

TCA48 Check Site Transplanting LSD (5%) CV (%)

Pusa Normal Delayed

Central Rice Normal Research Delayed Institute, Cuttack

Masodha Normal Delayed

Pooled mean Normal Delayed

Pooled LSD (0.05) Normal Delayed

4.0 2.3 0.5 15.7 2.7 2.0 0.4 15.1

2.4 0.7 0.6 17.7 2.7 1.5 0.8 17.8

3.5 1.8 1.0 29.0

3.3 2.7 0.7 0.6

IRRN 19:1 (March 1994) 15

Integrated germplasm improvement—rainfed lowland

– – –

– – – –

Influence of alkalinity on rice germination and growth J. C. Sharma, M. S. Kuhad, and A. P. Sharma, Soil Science Department, Haryana Agricultural University, Hisar 125004, India

We studied germination and seedling growth of six rice varieties at different pH levels. Tap water was used as the medium, with a pH of 7.0 and an EC of 1.0. Potassium hydroxide and acetic acid were used to adjust solution pH to 6.5, 7.5, 8.5, 9.5, and 10.5.

We placed 10 seeds of a variety in a petri dish, replicating each variety three times. Water volume was kept constant in each dish by adding solution. Germi- nated seeds were counted after 6 d. Seedling height and root length were measured at 6 and 10 d after transplant- ing (DT) (see table).

Overall germination ranged from 86 to 100% at all pH levels. Maximum germination for all varieties occurred at pH 8.5-9.5. HKR120 had the tallest seedlings at 6 DT. Seedling height,

Effect of alkalinity on growth of rice seedlings.

pH at 6 DT a pH at 10 DT Variety

6.5 7.5 8.5 9.5 10.5 Mean 6.5 7.5 8.5 9.5 10.5 Mean

Seedling height (cm)

Jaya 2.9 2.5 2.6 2.7 1.8 2.5 4.4 4.6 4.2 3.2 2.3 3.8 PR103 3.7 3.9 3.2 2.4 1.7 3.0 4.1 4.5 5.9 3.1 2.1 3.9 HKR120 3.2 4.8 3.9 3.3 1.8 3.4 4.2 4.7 5.4 3.3 1.9 3.9 PR106 3.1 3.3 2.9 2.6 2.8 2.9 4.2 4.4 4.5 3.2 3.6 3.9 PR109 2.4 3.1 2.6 2.4 1.7 2.4 3.4 4.3 4.4 2.9 2.5 3.5 Pal 579 3.3 3.0 3.1 3.6 2.0 3.0 3.9 4.2 4.6 4.0 2.5 3.9

Mean 3.1 3.4 3.1 2.8 1.2 4.0 4.5 4.8 3.3 2.5 LSD (0.05) V = 0.03, pH = 0.02, V × pH = 0.15 V = ns, b pH = 0.13, V × pH = ns

Root length (cm)

Jaya 2.6 2.6 2.4 3.1 1.8 2.5 3.5 3.6 3.2 2.6 1.6 2.2 PR103 4.9 6.1 4.7 2.1 1.4 3.8 5.2 6.6 5.6 1.9 1.4 3.1 HKR120 2.4 4.0 2.9 2.7 1.5 2.7 2.9 4.5 4.5 2.1 1.3 3.0 PR106 3.4 4.7 4.0 3.7 3.8 3.9 3.6 3.8 4.0 3.1 3.3 3.6 PR109 3.7 4.0 3.1 2.9 2.1 3.2 3.2 3.6 3.8 3.8 1.7 3.0 Pal 579 3.8 3.0 5.3 4.8 2.0 4.0 3.4 3.5 4.1 3.9 1.8 3.3

Mean 3.5 4.2 3.7 3.2 2.1 3.6 4.3 4.2 2.7 1.8 LSD (0.05) V = 0.01, pH = 0.10, V × pH = 0.65 V = 0.11, pH = 0.09, V × pH = 0.57

a DT = days after transplanting. b ns = not significant.

however, was not significantly different 10 DT. Pal 579 had the longest roots at among varieties at 10 DT. Seedlings were 6 DT and PR106 at 10 DT; Jaya had the tallest at pH 7.5 at 6 DT and at pH 8.5 at shortest. Roots were longest at pH 7.5.

Crop and resource management

Effect of green manures on ammonia-release pattern in rice soils R. Pushpavalli, K. Natarajan, and S. P. Palaniappan, Centre for Soil and Crop Management Studies, Tamil Nadu Agricul- tural University, Coimbatore 641003, India

We conducted an incubation study on a submerged clay loam (Vertic Ustropepts) and sandy loam (Typic Haplustalf) with green manure (GM) incorporation. Ipomoea ( Ipomoea cornea ), water hyacinth ( Eichhornia crassipes ), gliricidia ( Gliricidia sepium ), dhaincha ( Sesbania aculeata ), neem ( Azadirachta indica ), and calotrophis ( Calotrophis gigantia ) were incorporated at 12.5 t/ha fresh weight. Water level was maintained

at 5 ± 1 cm to keep soil submerged. We monitored ammonia-release pattern from the soils at 4, 8, 12, 16, 20, 30. and 45 d after incorporation (DAI).

In the clay loam, peak NH 4 + -N

concentration was observed after 30 DAI for ipomoea and water hyacinth; the highest concentration was at 20 DAI for the other GMs. In the sandy loam, NH 4

+ -N concentration for all GMs increased progressively up to 20 DAI, after which it declined (see figure). This difference between soils could be related to their pattern degradation and minerali

N mineralization of green ma- nures. (a) Ipo- moea/water hyacinth. (b) Neem/ gliricidia/ calotrophis.

16 IRRN 19:1 (March 1994)

The higher alkalinity (CO 3 -2 + HCO 3

- ) in GM-amended treatments was attributed to an increase in partial pressure of CO 2 during GM decomposition. The sharp decline of NH 3 was commensurate with a decline of ammoniacal N concentration in floodwater, probably due to volatilization losses and downward movement by mass flow. Although NH 3 did not provide an absolute measure of ammonia loss, results suggest that percolating soils generally have lower potential for ammonia vola- tilization.

As expected, the direct estimate showed a low amount of ammonia volatilization, ranging from 2.9 to 9.0 kg N/ha (see table). The losses were selectively higher during the 7 d following fertilizer applica- tion in the GM plus urea treatment at transplanting compared with GM treat- ments and urea application at 21 or 42 DT; the GM plus no urea treatment showed lower volatile ammonia loss.

GM-amended wetland rice soils undergo lower volatilization losses when urea is applied at active tillering or panicle initiation rather than at transplanting. Ammonia volatilization, however, is not an important loss mechanism in soil with a high percolation rate.

of ammonia ( NH 3 ). Ammonia vola- tilization was estimated directly by capturing the ammonia flush from the soil in two acid traps per plot.

The NH 3 in floodwater peaked two days after fertilizer application, followed by a sharp decline on the third day. It remained low until urea was topdressed at 21 or 42 DT (see figure), at which time

NH 3 again increased rapidly. The values were higher in the GM plus urea treatments than in the urea treatments at transplanting and at topdressing, suggest- ing a higher potential of ammonia loss in GM-amended soil. Ammoniacal N con- centration and floodwater alkalinity sup- ported the observation (data not reported).

Laboratory and greenhouse studies on mineralization of green manure (GM) show that peak NH 4

+ -N release occurs about 10 d after incorporation. We studied the effects of urea application timing on floodwater parameters and ammonia volatilization in a wetland ricefield during 1990.

The soil is a calcareous, alluvial sandy loam (Typic Ustochrept) with pH of 8.4, 0.35% organic C, 0.06% total N, CEC of 5.3 c mol/kg, and percolation rate of 12 cm/d. Treatments included 60 kg N/ha as GM Sesbania aculeata; GM and various combinations of 60 kg N/ha as urea applied at transplanting, 21 d after transplanting (DT), and 42 DT; and 120 and 180 kg N/ha as urea applied in three splits (see table). The experiment was laid out in a randomized block design with three replications. Floodwater samples collected between 1200 and 1400 h were analyzed for pH, ammoniacal N, and temperature to calculate the vapor pressure

zation processes. The delay in ammonia release from the GM in the clay loam might be due to the soil's high buffering capacity and its behavior in supporting microflora under submergence, which are involved in mineralization and immobili- zation turnover.

S. aculeata, followed by ipomoea, had the highest NH4 + -N concentration of the

treatments in both soils up to 20 DAI. Soil traits, particularly texture and its Variation in the ammonia released could associated characteristics, influence be attributed to the type of GM added and decomposition of added organic material. to the degradation and subsequent N Similarly, chemical composition of mineralization from these materials. organic matter, such as lignin and total Unconventional GMs, such as ipomoea carbon, controls mineralization and and water hyacinth, degraded more release of plant nutrients. slowly than popular leguminous GMs S. aculeata and gliricidia.

Effect of urea application timing on ammonia volatilization in green manure- amended wetland rice soil R. S. Rekhi and M. S. Bajwa, Punjab Agricul- tural University (PAU), Ludhiana 141004, India

Effect of green manure and urea N on vapor pressure of ammonia in floodwater.

a Values in parentheses show kg N/ha applied at transplanting, 21 DT, and/or 42 DT. b GM supplied 60 kg N/ha.

Effect of urea and GM N on ammonia volatilization loss (kg N/ha) at different days after transplanting. PAU, Ludhiana, India.

Treatment Days after transplanting

0-4 4-7 7-10 10-21 21-25 25-30 30-42 42-47 47-52 Total

N (40-40-40) a 1.0 0.3 0.2 0.3 1.7 0.7 0.5 0.9 0.6 6.2 N (60-60-60) 1.7 0.9 0.4 0.4 1.9 0.8 0.5 1.8 0.8 9.0 GM b +N (0-0-0) 1.0 0.6 0.3 0.2 0.2 0.2 0.1 0.1 0.1 2.9 GM+N (60-0-0) 2.8 1.8 0.3 0.4 0.2 0.3 0.4 0.2 0.2 6.6

GM+N (0-0-60) 1.0 0.6 0.3 0.2 0.2 0.2 0.2 2.0 1.0 5.7 GM+N (20-20-20) 1.3 0.7 0.3 0.2 1.1 0.4 0.3 1.0 0.4 5.7

GM+N (0-60-0) 1.0 0.6 0.3 0.2 2.3 0.8 0.4 0.3 0.2 6.6

a Values in parentheses show kg N/ha applied at transplanting, 21 DT, and/or 42 DT. b GM supplied 60 kg N/ha.

IRRN 19:1 (March 1994) 17

NH 3

( NH 3 )

Seasonal influence on 5, 10, 15, and 20 d after transplanting placement of urea (DT), and 56 kg N/ha as urea in two supergranules in rice equal splits as a basal application and at

panicle initiation. All treatments received K. E. Savithri and M. R. C. Pillai, Kerala a uniform basal dose of 19.8 kg P/ha and Agricultural University, Thrissur 680654, 37.3 kg K/ha. Two seedlings/hill were lndia transplanted at 20- × 10-cm spacing. Placing urea supergranules (USG) in the Total rain was 2,393 mm during WS reduced zone is a practical method to and 239 mm during DS. Soil at the increase N use efficiency in transplanted experimental site is a sandy clay loam. lowland rice. Rice is grown in wet Soil characteristics are in Table 1. season (WS) (Apr/May-Sep/Oct) and Urea supergranules were not superior dry season (DS) (Sep/Oct-Dec/Jan) in over a split application of urea during Kerala, India. We investigated whether WS, but the effect of USG placement was the effects of USG placement on the significant during DS (Table 2). This crop differ for the seasons and whether seasonal difference was probably due to crop performance is affected by timing the sand in the soil and the different of USG placement.

The experiment was laid out in a randomized block design with four Fate of applied N in replications for two consecutive seasons traditional, modern, and at the Regional Agricultural Research conservation farming Station, Pattambi, Kerala. We applied 56 kg N/ha as USG at transplanting and

systems of lowland rice in Sri Lanka

Table 1. Soil characters of the experimental site. Pattambi, Kerala, India.

Physicochemical character pH 5.5 Organic C (%) 1.62 Total N (%) 0.18 Available P (kg/ha) 14.2 Available K (kg/ha) 191.0 CEC (meq/100 g soil) 13.9

Particle size distribution Sand (%) 64.3 Silt (%) 10.2 Clay (%) 24.1

Table 2. Seasonal influence on placement of USG. Pattambi, Kerala, India.

Grain yield (t/ha)

WS DS Difference Treatment

USG at transplanting 3.6 4.3 0.7 USG at 5 DT a 3.5 4.2 0.7 USG at 10 DT 3.3 4.3 1.0 USG at 15 DT 3.2 4.4 1.2 USG at 20 DT 3.5 4.5 1.0 Urea in 2 splits 3.7 4.0 0.3

LSD (0.05) ns b 0.3 0.4

a DT = d after transplanting. b ns = not significant.

18 IRRN 19:1 (March 1994)

G. Seneviratne and S. A. Kulasooriya, Botany Department, University of Peradeniya, Peradeniya, Sri Lanka

We compared the soil N fertility of' traditional and modern rice farming systems prevailing in Sri Lanka’s dry zone with that of conservation farming. Applied N availability, retention, and loss in rice were studied using the 15 N isotope technique.

The nutrient source in the traditional system is soil-incorporated vegetation that grows during the fallow period; that in the modem system is chemical fertilizer, applied according to Depart- ment of Agriculture recommendations (see table). Conservation farming involves a basally applied leguminous green manure ( Sesbania rostrata or S. speciosa ) followed by topdressed chemical fertilizers (half of the recom- mended N and all of the recommended P and K).

The study was conducted in a lowland site at Maha Illuppallama. The soil is Tropaqualf with pH of 7.3, 4.4% organic matter, 0.095% total N, and 94 µg

amounts of rain. Rainfall was heavy but intermittent in the WS, resulting in alternate wetting and drying of the soil. This caused more nitrification of USG than usual for a heavy soil despite deep placement. Heavy rains caused the nitrate N to be leached from the root zone. Nitrification rate during DS was expected to be the same, but the leaching loss was less due to low rainfall, resulting in higher efficiency of deeply placed USG. Timing of USG placement did not significantly influence rice yield during either season.

In sandy clay loam soils, USG effectively increases N use efficiency of lowland rice under low rainfall and controlled water situations. Placement can be done any time between transplanting and 20 DT.

available P/g soil. The experiment was laid out in a randomized complete block design with four replications, using 1- × 1-m isotope plots lined with polythene. Nutrient sources and their 15 N-labeled materials were alternately applied to plots to trace the dynamics of plant and chemical fertilizer N. Rice variety BG38/4 was transplanted. The crop harvest, stubble, and soil were analyzed at harvest for total N and 15 N.

S. speciosa applied under conservation farming removed the most soil-incorpo- rated plant N through crop harvest (see table). Significantly large amounts of soil- incorporated plant N were found in stubble with S. speciosa application and the traditional system when compared with S. rostrata application.

The biggest loss of soil-incorporated plant N was with S. rostrata, meaning that the soil did not retain it well. Chemical fertilizer did not show significant differ- ences among the systems except for its high retention in stubble under S. speciosa. S. rostrata appeared to stimulate the release of soil N (positive added N interaction), as reflected in the crop harvest.

The low net N removal from the traditional system is probably compen- sated for by the biological N 2 fixation (BNF) associated with soil-incorporated materials from natural fallow. Soil N

Fate of applied N in traditional, modern, and conservation farming systems. a Maha Illuppallama, Sri Lanka.

Applied N Removal by crop harvest Retained in stubble Retained in soil Losses b Net removal Farming system (kg/ha) (kg N/ha) (kg N/ha) (kg N/ha) (kg N/ha) of N from

farming PI Cf PI Cf so PI Cf so PI Cf PI Cf system

(kg/ha)

Traditional: natural 63 - 7.6 - 28.7 b 1.1 4.4 b 23.6 - 30.7 5.1 c

Modern: full amount - 87 - 16.1 28.3 b - 1.7 3.5 c - 9.4 - 59.8 18.7 b fallow incorporation (12.1 b) (1.7 a) (37.5 a) (48.7 b)

recommended (18.8 a) (2.0 b) (10.8 a) (68.7 a) chemical fertilizer

Conservation: a) S. rostrata + 40 44 4.5 9.4 36.4 a 0.6 1.1 4.9 ab 4.8 6.1 30.1 27.4 25.3 a

1/2 recommended (11.7 b) (20.3 a) (1.0 b) (2.5 b) (12.0 c) (13.9 a) (75.3 a) (62.3 a) chemical fertilizer

1/2 recommended (16.6 a) (21.9 a) (2.0 a) (3.9 a) (29.7 b) (8.2 a) (51.7 b) (65.5 a) chemical fertilizer

b) S. speciosa + 30 44 5.0 9.9 30.6 b 0.6 1.7 5.4 a 8.9 3.6 15.5 28.8 17.9 b

LSD (0.05) 4.2 7.5 2.9 0.6 0.6 0.6 7.6 6.7 9.3 7.4 2.3 CV (%) 19.3 23.0 4.71 17.2 10.4 7.03 14.2 30.5 7.94 5.67 7.34

a Pl = plant (green manure/natural fallow), Cf = chemical fertilizer, So = soiI. Values within parentheses indicate amounts as percentages of applied N. In the same column, values followed by the same letter are not significantly different at the 0.05 probability level. b Losses from soil through leaching to subsoil. denitrification. and NH 3 volatilization.

fertility is sustained because rice straw balance in ricefields. This tends to increase nonsymbiotic BNF. More data incorporation can fix 20 kg N/ha. Other

chemical N fertilizer brings negative N soil under flooded condition could rating fresh leaves of Sesbania spp. into tion farming. in the modem system because adding

sustainability of N fertility in conserva- has, however, been reported that incorpo- sources do not replenish net N removed are needed to fully evaluate the decrease soil N fertility in the long run. It

Occurrence of rice tungro disease in central Vietnam Ngo Vinh Vien, Ha Minh Trung, Plant Protection Research Instltute, Chem, Tu Liem, Hanoi, Vietnam; and H. Koganezawa, IRRI

Symptoms similar to those of rice tungro disease (RTD) were first observed in Vietnam in 1982. The disease reached epidemic levels in 1990 on about 20,000 ha of summer-autumn rice grown in Khanh Hoa, Binh Dinh, Phu Yen, and

Retention period of the agent of yellow leaf symptoms in GLH.

Days after acquisition

No. of infective insects a

1 42 2 36 3 20 4 8 5 2 6 0

a 70 GLH were tested.

Quang Nam-Da-Nang provinces in central Vietnam.

The usual symptoms were yellow leaves and stunting. Leaf discoloration started from the tip, and mottle symptoms were sometimes observed on young leaves. Plants infected early often had delayed flowering, small panicles, and a high percentage of sterile and unfilled or empty grains. Although late-infected plants did not show any symptoms, ratoons grown from their stubble did. Varieties IR17494, IR8, IR9823, Binh dinh, CN47, CN78, VL 12, and LD84 were severely affected; IR64, TH28, IR68, and KSB21 were considered resistant.

As RTD had never before been reported in the region, we conducted insect transmission tests and an enzyme- linked immunosorbent assay (ELISA). Preliminary tests using insects with 10-d acquisition periods and 24-h inoculation periods indicated that the green leafhopper (GLH) transmitted the

disease, but not the brown planthopper or whitebacked planthopper.

manner by allowing 70 GLH to feed on infected IR17494 plants for 24 h. GLH were transferred serially onto 10-d-old seedlings in tubes for a 24-h inoculation access time. Forty-five GLH transmitted the disease. Maximum retention period of the agent in GLH was 5 d (see table).

These results indicate that GLH transmits the disease in a semipersistent manner. Using ELISA, we detected both rice tungro spherical virus and rice tungro bacilliform virus in infected plants. Therefore, RTD is the cause of the yellow leaf symptoms.

We examined the transmission

IRRN 19:1 (March 1994) 19

-

Thrips affected by steam distillates of resistant varieties and wild rices R. Velusamy, M. Ganesh Kumar, and Y. S. Johnson Thangaraj Edward, Agricultural Entomology Department, Tamil Nadu Agriultural University (TNAU), Coimbatore 641003, India; and B. Thayumanavan and S. Sadasivam, Biochemistry Department, TNAU

Extracts of steam distillates of varieties Ptb21, Rathu Heenati, and Swarnalata and wild rices Oryza officinalis (Acc. 101114) and O. latifolia (Acc. 100963) were bioassayed against greenhouse- reared Stenchaetothrips biformis (Bagnall).

insectproof screenhouse were harvested and ground with an electric grinder. Distillation and extraction were done following the Saxena and Skech method developed at IRRI.

16-cm-diam pots. Single tillers of 30-d- old plants were sprayed with 1 ml of acetone-water solution containing extract at the rate of 2,000 ppm. Controls were treated with acetone or nothing.

on oviposition behavior of thrips, each plant was infested with five gravid females and then covered with a mylar cage. Eggs were counted 3 d after their release.

To determine toxicity, ten 1st-instar larvae were placed on each seedling after the acetone had evaporated; the seedling was then covered with a mylar cage. Larval mortality was recorded after 24 h. Each treatment was replicated five times and arranged in a randomized complete block design.

All of the extracts adversely affected the ovipositional behavior of S. biformis (see table). The wild rice extracts were more effective than those of the resistant varieties.

Leaves of 30-d-old plants grown in an

Susceptible TN1 plants were grown in

To determine the effect of the extracts

Al1 of the extracts were toxic to some degree to 1st-instar thrips. The wild rice extracts were most toxic (see table).

Effect of steam distillate extracts of resistant varieties and wild rices on S. biformis ovipositional behavior and larval mortality. a

Treatment Eggs laid (no.) Larval mortality (%)

Control 25 a ± 1.30 2 c ± 0.63 Control (acetone) 22 a ± 1.30 Ptb21

4 c ± 0.63 9 cd ± 0.71 40 b ± 3.16

Rathu Heenati 11 bc ± 0.71 44 b ± 2.45 Swarnalata 13 b ± 1.14 36 b ± 4.00 O. officinalis 4 e ± 0.71 82 a ± 3.74 O. latifolia 7 de ± 0.71 76 a ± 5.10

SEM 1.24 3.35

a Mean of 5 replications. In a column, means followed by a common letter are not significantly different at the 5% level by DMRT.

Sampling spiders during the rice fallow period G. S. Arida and K. L. Heong, IRRI

Spiders commonly found on growing rice either migrate to nonrice environments after harvest or remain within the harvested field, residing in soil crevices or on bunds during the fallow period. Methods to sample arthropod populations from growing rice are not adequate for sampling crevices during the fallow period.

techniques in a ricefield in Nueva Ecija, number of spiders Philippines, 3 wk after harvest. The field collected per m 2

was dry with soil crevices about 40 cm from soil crevices 3 wk after rice

deep. A square (1 × 1 × 0.3 m) metal harvest. Nueva frame (gauge #12) was placed randomly Ecija, Philippines. in the field and hammered 5 cm below 1993 dry season. ground level. A sticky material (Tanglefoot) was applied in a 5-cm-wide strip on both the outside and inside of the of water per frame were poured into the frame above ground level to prevent crevices; in the third, the crevices were spiders from moving in and out of the opened with a metal bar. For all methods, sampling area. The experiment was spiders leaving the crevices were either replicated four times. collected by hand or were caught in the

Spiders in the enclosed area were sticky material and then collected. The sampled by simple observation, pouring frames were left overnight and catches on water inside the frame, and digging into the inside were later gathered. the crevices. With the first technique, Results show that spiders inhabited spiders were observed for some time and field crevices even at 3 wk after harvest then caught as they emerged from (see figure). Pouring water inside a frame crevices. Individuals trapped in the metal appears to be an effective sampling frames were also collected. The other method and is especially good for techniques involved forcing the arthro- catching jumping spiders, such as pods out: in the second, about 300 liters Pardosa sp.

We compared different sampling Species and

20 IRRN 19:1 (March 1994)

Host plant range of Pseudococcus saccharicola

released per cage in a no-choice test. Host suitability was based on surviv- orship and nymphal stage duration of the Takahashi issuing progeny. Each cage was a

J. L. A. Catindig and A. T. Barrion, IRRI; and J. A. Litsinger, 1365 Jacobs Place, Dixon,

treatment in a randomized complete

CA 95620, USA

Mealybug P. saccharicola sometimes house at an average temperature of 28.0 ± occurs on rice cultured in the greenhouse. 1.2 °C and 66.0 ± 2.9% relative humidity. We compared its development on 24 Nymphs survived on 17 of the 24 common ricefield plants from families Poaceae (20) and Cyperaceae (4). higher survival rates occurred with rice

plants tested (see table). Significantly

Twenty-five- to 30-d-old individual (90.6%), Echinochloa glabrescens host plants were maintained in 20-cm- (81.2%), and Panicum repens (80.5%). diam clay plots. Plants were covered with The most progeny per female were 10- x 72-cm cylindrical mylar cages with produced on P. repens (39.0 nymphs) and side and top nylon mesh (1 mm2) vents. E. glabrescens (38.2 nymphs). The Five pairs of newly emerged adults were shortest life cycles—and therefore the

block design with 10 replications. The experiment was conducted in the green-

most nutritious hosts—occurred on rice and E. glabrescens (21.0 d), followed by Triticum aestivum (21.5 d) and Paspali- dium,flavidum (22.2 d).

Plant hosts were ranked overall and for each life cycle parameter by taking the average of the survival, progeny, and life cycle rankings. The top-ranked hosts overall were rice > E. glabrescens = P. repens > Leptochloa chinensis. Ischae- mum rugosum and Cyperus iria were the least acceptable hosts with the lowest nymphal survival of 9.0- 11.6% and the longest life cycle of 25.2-26.0 d. Seven species—four Poaceae and three Cyperaceae—were not hosts of P. saccharicola.

Host plant range of P. saccharicola a . IRRI greenhouse, Feb-May 1990.

Parameter

Host

Poaceae TN1 rice Echinochloa glabrescens Munro ex Hook f. Panicum repens L. Leptochloa chinensis (L.) Nees Triticum aestivum L. em. Thell. Echinochloa colona (L.) Link Brachiaria mutica (Forsk.) Stapf. Paspalidium flavidum (Retz.) A. Cameron Cynodon dactylon (L.) Pers. Paspalum conjugatum Berg. Leersia hexandra Sw. Paspalum scrobiculatum L. Eleusine indica (L.) Gaertn. Paspalum paspalodes (= P. distichum L.) Brachiaria distachya (L.) Stapf. lschaemum rugosum Salisb.

Overall Nymphal survival Progeny Duration of average

(%) b (no. crawlers/female) life cycle (d) c ranking d

90.6 ± 4.2 a 30.5 ± 4.5 bc 21.0 ± 0.8 a 1 81.2 ± 2.5 ab 38.2 ± 6.2 ab 21.0 ± 2.2 a 2 80.5 ± 10.8 ab 39.0 ± 10.5 a 25.0 ± 0.8 cd 2 70.4 ± 21.1 bc 19.0 ± 9.4 de 22.8 ± 3.9 bc 3 63.9 ± 18.0 b d 13.5 ± 4.4 ef 21.5 ± 0.6 a 4 50.4 ± 18.3 de 17.8 ± 5.6 d f 22.8 ± 2.1 bc 5 58.8 ± 11.2 cd 12.2 ± 3.1 ef 24.8 ± 1.5 cd 6 11.2 ± 6.0 gh 23.2 ± 9.0 cd 22.2 ± 4.8 ab 7 26.8 ± 18.0 fg 15.5 ± 10.2 def 25.2 ± 2.5 cde 8 40.2 ± 32.3 ef 13.0 ± 8.5 ef 27.2 ± 1.0 def 9 25.6 ± 11.1 fg 15.2 ± 5.1 def 30.0 ± 2.9 f 10 28.9 ± 21.1 fg 8.5 ± 4.7 f 30.8 ± 1.3 f 11 11.6 ± 5.1 gh 16.2 ± 3.9 d f 27.0 ± 1.6 def 12 14.0 ± 3.1 gh 19.2 ± 7.1 de 26.5 ± 1.3 def 12 12.1 ± 6.3 gh 12.2 ± 3.1 ef 28.8 ± 0.5 def 13

9.0 ± 1.6 gh 11.5 ± 2.4 ef 26.0 ± 3.4 def 13

Cyperaceae Cyperus iria L. 11.6 ± 9.2 gh 12.5 ± 7.0 ef 25.2 ± 2.5 c-e 13

a Av of 10 replications. In a column, means followed by a common letter are not significantly different (P < 0.01) by LSD statistical test. No nymphs survived on Chloris barbata Sw.,

L., and C. kyllingia Endl. in the Cyperaceae family. Eriochloa procera (Retz.) C. E. Hubb., lmperataca cylindrica (L.) Beauv., and lsachne globosa (Thund.) O. K. in the Poaceae family, or on Cyperus brevfolius (Rottb.) Hassk., C. rotundus

b Nymphal survival (%) = Crawlers becoming adults (no.)

lnitial crawlers (no.) × 100. c n = 10. d 1 = best, 13 = worst.

IRRN 19:1 (March 1994) 21

Host plant range of leafhopper Cicadulina bipunctata (Melichar) J. L. A. Catindig and A. T. Barrion, IRRI, and J. A. Litsinger, 1365 Jacobs Place, Dixon, CA 95620, USA

C. bipunctata is commonly found in habitats associated with rice, and it can vector rice diseases such as rice leaf gall and stripe virus. Its development was studied on 33 common ricefield plants belonging to families Poaceae (24), Cyperaceae (6), and Leguminosae (3). Each species was established in 20-cm- diam clay pots.

Five pairs of newly emerged adults, from a colony maintained on rice in a greenhouse, were released onto 25- to 30- d-old individual host plants enclosed in 10- × 72-cm cylindrical mylar cages with

side and top nylon mesh (1 mm 2 ) vents. Insects were allowed to oviposit for 5 d. Nymphal survival and fecundity were used to determine host suitability. Each caged plant served as a treatment. The no-choice experiment was replicated 10 times in a randomized complete block design in a greenhouse where tempera- ture averaged 27.6 ± 1.5°C and relative humidity, 66.8 ± 3.1%.

from Cyperaceae supported complete development of the leafhopper. Percent- age survival was highest on maize (93.5%), Digitaria sanguinalis (91.8%), Paspalum paspalodes (88.6%), and Ischaemum rugosum (75.4%). Survival was lowest on wheat (7.0%) and Cyperus rotundus (1.0%) (see table).

The shortest nymphal duration was recorded on maize (18.6 d), Echinochloa

Eighteen plants from Poaceae and one

colona (20.5 d), and Eriochloa procera (21.4 d). The longest duration was on C. rotundus (25.0 d).

(729/5 females) and the least (0.4-0.7/5 females) on two Cyperus spp. Five ovipositional hosts, four Poaceae and one Cyperaceae, failed to support complete insect development.

Maize was ranked as the best accepted host as it had the highest nymphal survival and shortest nymphal duration. It was followed by P. paspalodes > D. sanguinalis > I. rugosum > Paspalidium flavidum, C. rotundus was the least fit host with the lowest survival and longest duration. Nine species—two Poaceae, four Cyperaceae, and three Leguminosae—did not support C. bipunctata.

Females laid the most eggs on maize

Host plant range of C. bipunctata. a IRRI greenhouse, Jan-May, 1990.

Parameter Host Overall

Nymphal survival (%) b Nymphal duration (d) c Eggs laid average (no./5 females) ranking d

Poaceae Maize 93.5 ± 4.6 a 18.6 ± 2.4 a 729.0 ± 344.1 a 1 Paspalum paspalodes (= P. distichum) 88.6 ± 13.6 ab 22.5 ± 0.7 b-e 88.5 ± 41.7 b 2 Digitaria sanguinalis (L.) Scop. 91.8 ± 5.2 a 24.0 ± 0.5 f 82.6 ± 37.2 bc 3 Ischaemum rugosum Salisb. 75.4 ± 21.0 a-c 23.5 ± 1.1 de 44.8 ± 32.5 b-d 4 Brachiaria distachya (L.) Stapf. 66.7 ± 42.7 b-e 22.6 ± 2.1 b-e 29.5 ± 28.7 b-d 5 Echinochloa glabrescens Munro ex Hook f. 66.3 ± 46.3 b-e 22.1 ± 0.6 b-d 19.9 ± 18.8 cd 5 Paspalidium flavidum (Retz.) A. Cameron 71.2 ± 38.2 a-d 23.9 ± 1.8 ef 66.5 ± 47.5 b-d 6 Echinochloa crus-galli (L.) Beauv. ssp. hispidula 54.2 ± 47.2 c-f 22.1 ± 0.6 bd 19.7 ± 12.1 cd 7

E. colona (L.) Link 47.9 ± 22.1 d-g 20.5 ± 2.1 ab 16.8 ± 10.1 d 7 Eriochloa procera (Retz.) C. E. Hubb 49.2 ± 39.6 d-g 21.4 ± 2.2 ac 20.5 ± 13.1 cd 7 Paspalum scrobiculatum L. 64.3 ± 33.9 b-e 23.6 ± 5.1 ef 26.9 ± 24.2 b-d 8 Eleusine indica Gaertn. 43.9 ± 27.8 e-g 22.5 ± 1.8 b-e 44.8 ± 34.3 b-d 9 Panicum repens L. 61.4 ± 34.7 c-e 23.7 ± 0.7 ef 19.7 ± 18.2 cd 10 Brachiaria mutica (Forsk.) Stapf. 45.0 ± 34.0 e-g 22.5 ± 0.9 b-e 11.7 ± 9.9 d 11 Leptochloa chinensis (L.) Nees 26.2 ± 14.6 gh 23.6 ± 1.7 ef 2.4 ± 1.9 d 12 Rice TN1 30.2 ± 25.4 f-h 24.0 ± 0.5 f 15.3 ± 13.6 d 12

lmperata cylindrica (L.) Beauv. 8.0 ± 4.2 hi 23.5 ± 1.3 de 3.4 ± 2.4 d 13 Wheat 7.0 ± 4.8 hi 23.1 ± 1.1 de 3.0 ± 1.2 d 13

Cynodon dactylon (L.) Pers. e 0 0 h 8.5 ± 7.7 d 15

Chloris barbata Sw. e 0 0 h 7.6 ± 4.7 d 15 Paspalum conjugatum Berg. e 0 0 h 2.2 ± 2.0 d 15 Leersia hexandra Sw. e 0 0 h 1.0 ± 0.8 d 15

Retz Honda

Cyperaceae Cyperus rotundus L. C. difformis L. e

1.0 ± 0.8 i 25.0 ± 0 g 0.7 ± 0.5 d 14 0 i 0 h 0.4 ± 0.2 d 15

a Av of 10 replications. In a column, means followed by a common letter are not significantly different (P < 0.01) by LSD statistical test. Nymphs did not survive and eggs were not laid on Sorghum halepense (L.) Pers. and lsachne globosa (Thund.) O. K. In the Poaceae family; on C. brevifolius (Rottb.) Hassk., C. iria L., C. diffusa L., and Fimbristylis miliacea L. In the Cyperaceae family; and on soybean, mungbean, and cowpea in the Leguminosae family.

b Survival (%) = Nymps becoming adults (no.)

lnitial nymphs [no.) × 100. c n = 10. d 1 = best, 15 = worst. e No nymphs survived.

22 IRRN 19:1 (March 1994)

i i i i

Developmental biology and host plant range of rice ear- cutting caterpillar Mythimna separata (Walker) J. L. A. Catindig and A. T. Barrion, IRRI; and J. A. Litsinger, 1365 Jacobs Place, Dixon, CA 95620, USA

Forty-one common ricefield plants from families Poaceae (25). Cyperaceae (6), Commelinaceae (3), Leguminosae (3), and one each from Amaranthaceae, Pontederiacea, Portulacaceae, and Onagraceae were evaluated as host plants to M. separata.

Ten unfed newly emerged larvae from a culture maintained on rice in a green- house were placed on a 25- to 30-d-old test plant in a 20-cm-diam clay pot within a 10- × 72-cm cylindrical mylar cage with side and top nylon mesh (1 mm 2 ) vents. Each cage was a treatment. Host suitabil- ity was determined by percentage of larval survival to pupation, larval developmental period, and number of eggs laid/female. The no-choice experi- ment was replicated 10 times in a

randomized complete block design conducted in a greenhouse where temperature averaged 26.7 ± 0.9 °C and relative humidity, 72.4 ± 4.5%.

Ovipositional preference and fecun- dity were also determined in a no-choice experiment. Two 3- to 5-d-old pupae reared on rice were placed in a larval developmental cage as described above. Honey solution (10%) in a cotton mesh provided food for the moths.

Thirty-one plant species supported complete larval development (Table 1). Larval survival to pupation was highest on Leptochloa chinensis (58%), Isachne globosa (54%), Paspalum paspalodes (53%), and rice (51 %). Larval survival was not higher (<80%) due to mold infections. Larval development was shortest on rice (19.2 d), which was significantly shorter than on L. chinensis (21.7 d). Development was longest on Imperata cylindrica (34.8 d) and Brachiaria distachya (37.8 d).

All 41 species were accepted as ovipositional hosts. Preference was rice > Paspalum scrobiculatum > Digitaria

ciliaris > P. paspalodes > Leersia hexandra > I. globosa. Females laid the fewest eggs on Commelina diffusa, mungbean, Dactyloctenium aegyptium, and Ludwigia octovalvis.

Moths laid smooth, shiny yellowish- white spherical eggs in rows. On rice, egg incubation lasted 3 d and larvae passed five stadia in 20 d (Table 2). Prepupation lasted 2.0 d and pupation, 8.3 d. Total development from egg to adult emer- gence was 30.2 d and female longevity was 10.8 d. Fecundity was 220 ± 59.6 eggs/female.

M. separata larvae, although polyphagous, showed incomplete development on 10 species: three in Poaceae, two in Commelinaceae, and one each in Leguminosae, Amaranthaceae, Pontederiaceae, Portulacaceae, and Onagraceae (Table 1). Overall host ranking was rice > L. chinensis > P. paspalodes > P. conjugatum > E. colona.

Table 1. Comparative developmental biology of M. separata on 41 plants. a IRRI greenhouse, May-Mar 1990.

Parameter Host

Poaceae Rice TN1 Leptochloa chinensis (L.) Nees Paspalum paspalodes (= P. distichum L.) P. conjugatum Berg. Echinochloa colona (L.) Link lsachne globosa (Thunb.) O. K. Echinochloa crus-galli (L.) Beauv. ssp. hispidula

Cynodon dactylon (L.) Pers. Maize Eleusine indica Gaertn. Echinochloa glabrescens Munro ex Hook f. Chloris barbata Sw. Digitaria ciliaris (Retz.) Koel. Leersia hexandra Sw. Digitaria sanguinalis (L.) Scop. Eriochloa procera (Retz.) C. E. Hubb. Paspalum scrobiculatum L. Dactyloctenium aegyptium (L.) Beauv. Triticum aestivum L. em. Thell. Paspalidium flavidum (Retz.) A. Cameron Brachiaria distachya (L.) Stapf.

(Retz.) Honda

Nymphal survival (%) b Nymphal duration (d) c Eggs laid (no./5 females)

51.0 ± 1.5 ab 19.2 ± 0.8 a 220.0 ± 59.6 a 58.0 ± 19.3 a 21.7 ± 0.8 ab 76.9 ± 3.8 def 53.0 ± 18.9 ab 26.8 ± 2.6 ef 135.0 ± 16.9 bc 31.0 ± 3.2 cde 22.2 ± 0.9 bc 45.4 ± 9.3 f-l 47.0 ± 13.4 ab 27.9 ± 0.7 fh 73.0 ± 86.4 d-g 54.0 ± 19.0 a 30.7 ± 1.2 i-k 121.3 ± 58.6 c 42.0 ± 18.7 bc 29.2 ± 1.1 h-k 34.5 ± 13.0 h-o

33.0 ± 24.1 cd 27.6 ± 1.4 f-h 5.8 ± 4.4 no 30.0 ± 11.6 def 26.9 ± 0.7 fg 10.5 ± 5.3 l-o 33.0 ± 13.4 d-i 25.0 ± 0.9 cd 29.4 ± 8.4 i-o 31.0 ± 15.3 cde 29.7 ± 1.0 h-k 50.1 ± 15.5 e-k

23.0 ± 21.6 d-i 27.7 ± 1.0 f-h 143.7 ± 53.0 bc 19.0 ± 12.0 e-j 27.9 ± 0.7 f-h 124.6 ± 1 9.1 bc

16.0 ± 5.2 g-j 32.0 ± 0.9 j-l 21.8 ± 10.7 k-o 30.0 ± 17.0 def 36.4 ± 0.7 m 154.0 ± 61.1 b 13.0 ± 4.8 h-m 29.0 ± 0.7 f-i 1.7 ± 1.1 no

2.0 ± 0.3 I-n 32.0 ± 1.5 j-l 58.9 ± 41.4 d-j 3.0 ± 2.8 k-n 37.8 ± 0.8 n 62.1 ± 34.5 d-i

26.0 ± 14.5 d-g 29.1 ± 0.9 g-j 79.3 ± 55.7 de

15.0 ± 9.7 g-k 26.0 ± 2.0 de 21.8 ± 9.7 k-o

24.0 ± 18.4 d-h 29.0 ± 1.3 cd 43.4 ± 23.9 g-m

Overall average ranking d

1 2 3 4 5 6 7

8 9

10 11 12 13 14 15 16 18 22 23 24 26

continued on next page

IRRN 19:1 (March 1994) 23

Table 1 continued

Host Parameter

Overall Nymphal survival (%) b Nymphal duration (d) c Eggs laid average

(no./5 females) ranking d

lmperata cylindrica (L.) Beauv. Panicum repens L. Brachiaria mutica (Forsk.) Stapf. Bambusa sp.

1.0 ± 0.2 mn 0

34.8 ± 1.6 I 22.2 ± 13.2 k-o n 0 0 4.3 ± 9.3 no

0 n 0 0 65.8 ± 10.8 d-h 0 n 0 0 21.4 ± 10.2 k-o

26 27 28 29

Cyperaceae Cyperus iria L. C. rotundus L. C. kyllingia Endl. C. difformis L. Fimbristylis miliacea (L.) Cyperus brevifolius (Rottb.) Hassk.

Commelinaceae Commelina diffusa Burm. f. Murdannia nudiflora (L.) Commelina benghalensis L.

30.0 ± 14.1 def 27.9 ± 1.1 f-h 26.6 ± 17.1 j-o 11 18.0 ± 15.5 f-j 28.2 ± 0.9 f-h 28.0 ± 19.1 i-o 17

8.0 ± 6.3 j-n 29.5 ± 1.6 h-k 15.8 ± 8.9 l-o 20 3.0 ± 2.8 k-n 33.8 ± 0.8 kl 36.7 ± 23.2 h-n 25

14.0 ± 5.2 h-l 28.3 ± 1.4 f-h 43.3 ± 19.0 g-m 19

27.0 ± 16.4 d-g 31.0 ± 0.8 i-k 85.8 ± 44.1 d 30

11.0 ± 3.2 i-n 28.9 ± 0.6 fi 7.8 ± 4.7 no 21 0 n 0 0 19.8 ± 9.0 k-o 29 0 n 0 0 12.4 ± 9.6 l-o 33

Leguminosae Soybean Mungbean Cowpea

Amaranthaceae Amaranthus spinosus L.

Pontederiaceae Monochoria vaginalis (Burm. f.) Presl.

Portulacaceae Portulaca oleraceae L.

1.0 ± 0.5 mn 29.7 ± 1.1 h-k 18.9 ± 17.0 k-o 22 1.0 ± 0.7 mn 30.8 ± 0.9 i-k 2.1 ± 2.6 no 25 0 n 0 0 24.0 ± 16.5 k-o 29

0 n 0 0 30.9 ± 16.2 i-o 29

0 n 0 0 14.1 ± 4.6 l-o 32

0 n 0 0 10.3 ± 3.3 mno 31

Onagraceae Ludwigia octovalvis (Jacq.) Raven 0 n 0 0 1.1 ± 1.00 34

CV (%) 66.4 66.5 66.6 LSD (0.1) 36.7 13.9 0.6 LSD (0.5) 27.9 10.6 0.5

a Av of 10 replications. In a column, means followed by a common letter are not significantly different (P <0.01) by LSD statistical test.

b survival (%) = × 100. c n = 10. d 1 = best, 34 = worst. Larvae pupating (no.)

Total larvae (no.)

Table 2. Life history of M. separata. a IRRI greenhouse, May-Mar 1990.

X ± SD

Egg incubation (d) 3.0 ± 0.4 Larval stadium (d) genera and 9 families were recorded in 30 nurseries in Kafr El-Sheikh

Weed species in rice seedling Twenty species belonging to 13

I 3.4 ± 0.7

RRTC, Sakha, Kafr El-Sheikh, Egypt commonly were Cyperus difformis, V 4.9 ± 0.3

governorate, Egypt II

nurseries. Grasses and broad-leaved weeds accounted for 74% of the species 3.2 ± 0.4

III 4.0 ± 0.7 Center (RRTC), and A. N. Rao, IRRI/Egypt, IV 4.4 ± 0.5 S. M. Hassan, Rice Research and Training (see table). Those occurring most

Prepupa (d) 2.0 ± 0 Pupa (d) Total developmental period (d) 30.2 ± 2.0 Moth longevity (d) Eggs laid (no./female) 220.0 ± 59.6 governorate in Egypt during 1992 All of the farmers surveyed hand

Echinochloa crus-galli, Ammannia 8.3 ± 0.7 We surveyed weeds in farmers’ rice baccifera, E. colona, E. oryzoides, and

10.8 ± 2.8 seedling nurseries in Kafr El-Sheikh Dinebra retroflexa.

summer season. weeded the nurseries, achieving 50-70% a n = 10.

24 IRRN 19:1 (March 1994)

Weed species recorded in rice seedling nurseries in Kafr El-Sheikh governorate of Egypt. 1992 summer season.

Absolute Family presence a Constancy b

(n = 30)

Cyperus difformis L. Cyperaceae 28 0.93 Echinochloa crus-galli (L.) Poaceae 27 0.93

Ammannia baccifera L. Lythraceae 24 0.80 E. colona (L.) Link Poaceae 21 0.70 E. oryzoides (Ard.) Fritsch. Poaceae 17 0.5 Dinebra retroflexa (Vahl) Poaceae 16 0.5

Bergia capensis L. Elatinaceae 10 0.3 Cyperus longus L. Cyperaceae 10 0.3

E. phyllopogon Poaceae 9 0.30

Paspalum distichum L. Poaceae 9 0.30 A. multiflora Roxb. Lythraceae 9 0.30 Cyperus rotundus L. Cyperaceae 8 0.27 Leersia hexandra Sw. Poaceae 8 0.27 Eclipta prostrata (L.) L. Asteraceae 7 0.23 A. auriculata Willd. Lythraceae 7 0.23 Lemna gibba L. Lemnaceae 6 0.20 Xanthium strumarium L. Asteraceae 5 0.17 Lotus arabicus L. Fabaceae 4 0.13 Chara sp. Characeae 3 0.10 Azolla pinnata R. Br. Azollaceae 2 0.07

P. Beauv.

Panzer

(Stapf.) Koss.

weed control. Hand weeding cannot control Echinochloa spp. due to their morphological similarities with rice seedlings; they are therefore transplanted with rice.

The farmers all pulled seedlings in bunches, along with the soil, to avoid making rice seedling bundles. This is another practice that results in transplant- ing rice and weeds, including E. crus- galli, E. oryzoides, E. colona, and C. difformis.

Between 5 and 30% of rice hills were infested with transplanted weeds, which are highly competitive with rice.

a Number of nurseries in which the species was recorded. b Number of nurseries in which the species was recorded/total number of nurseries surveyed.

Slash-and-burn upland rice production in Bolivia’s chapare region J. A. Litsinger, 1365 Jacobs Place, Dixon, CA 95620, USA; E. Ayala and D. Cruz, lnstituto Boliviano de Tecnologia Agropecuaria, Casilla no. 4067, Cochabamba, Bolivia

The chapare region of the Department of Cochabamba in Bolivia is located at the foot of the Andes in the Amazonian lowlands. Soils are acidic with pH of 4.0- 5.5. Annual rainfall declines progres- sively from 5,000 mm in the southwest to 2,500 mm in the northeast. Bolivia has more than 120,000 ha of rice; all of it is upland on nonsloping land, and most is grown under mechanization on large farms. More than 15,000 ha are planted under slash-and-burn culture, however, which represents 6-10% of the country’s total rice production of 225,000 t. About two-thirds of Bolivia’s slash-and-burn

rice is planted in the chapare. Farmers have holdings of 5-50 ha. Lowland farm families consume an average 0.6-1.2 t milled rice per year. We interviewed 31 farmers from eight villages in Mar 1993 to describe the prevailing system of rice culture.

Rice is normally planted in Oct with the onset of the wet season. The forest is cleared from Jul to Sep during dry season. Farmers slash brush and fell trees ( chacear ), with time spent clearing depending on number of trees and average tree diameter. Virgin forests require a mean 36 d/ha to clear while regrowth ( chume ) requires a mean 26 d/ha. Brush and trees are left to dry for 1-2 mo before burning. Logs left after the first burn are piled for a second burning

On cleared virgin forest land, farmers usually plant two rice crops, followed by maize and/or cassava in the third year. The land is fallowed for an average of 7 yr before being returned to rice.

On the chume land, few soils are

(9 d/ha).

sufficiently fertile for two consecutive rice crops. Land is left fallow for an average of 3 yr after cropping. In richer chume soils, banana follows the second year; in poorer soils, citrus and other fruits are planted. In the least fertile chume areas, rice is planted after clearing, and land is then fallowed for 3-7 yr before again planting rice.

Most popular cultivars are long- grained and about 1 m tall. Blue Bonnet was grown by 31% of the farmers during the 1992-93 season, followed by Pico Negro (23%), Carolina (22%), Blue Belle (8%), Cateto (8%), CICA8 (4%), Dominicana (2%). and Argentina (2%). Blue Bonnet, CICA8, Dominicana, and Argentina mature in 140 d, the others in 90 d. Farmers prefer later maturing cultivars for higher yield and earlier maturing ones to escape pests or for more immediate food consumption.

Seeds are planted in hills 25-40 cm apart using a dibble stick; on average, 9 seeds/hill are used. No purchased fertilizer is used. Virgin forest land

IRRN 19:1 (March 1994) 25

Weed species

Due to availability of irrigation water in India’s northern Bihar region, rice-based sequences of two or three crops a year have replaced the traditional rice mono- crop. Irrigation water availability varies in the region.

We studied the performance of various cropping sequences under different water regimes. The experiment was conducted in a medium lowland site at the RAU Farm with five cropping sequences: rice - wheat - green gram, rice - winter maize - black gram, rice - potato - green gram, rice - Indian mustard - green gram, and rice - gram (chickpea) - green gram. Three levels of irrigation treatments were used in winter and summer seasons based on either irrigation water depth-cumulative pan evaporation ratio (IW:CPE) or days after sowing. Early rice variety Saket was transplanted on 20-25 Jul during 1986-91;

require an average of 0.8 weeding (mean of 8 d/ha) the first year and 1.6 weedings (17 d/ha) the next compared with chume land at 2.3 weedings (21 d/ha). Fifty-four percent of farmers sprayed insecticide for the large plant-sucking insect petilla ( TiBraca limbativentris ) or seed bugs. Some farmers reported losses to petilla of

Rice is harvested panicle-by-panicle with a hand knife, and threshing is done by foot. Rice is not winnowed. Yields

50-80%.

reported from the past two seasons averaged 0.8 t/ha. The highest yield any farmer obtained was 3.7 t/ha.

All of the farmers indicated weeds and lack of fertility to be their most important constraints, followed by petilla (80% of respondents). Other problems were mentioned by less than 27% of the farmers.

Other insect pests are grasshoppers and spittle bug ( Zulia sp.). Common diseases are both leaf and neck blast,

brown leaf spot, narrow brown spot, and leaf scald. Blast is the most important of these, but it does not cause yield loss every year.

involved in slash-and-burn rice culture and stagnated yields, rainfed puddled rice culture might be an alternative in this high-rainfall area.

Because of the high labor input

Yield ability and net return of rice-based cropping sequences under different water regimes in Bihar, India Crop sequence Suboptimal Optimal Supraoptimal

Table 2. Rice equivalence yield and net profit as influenced by irrigation levels and types of cropping sequences. a Bihar, India. 1986-91.

Level of irrigation

U. K. Prasad, T. N. Prasad, and R. D. Singh, Agronomy Department, Rajendra Agricultural University (RAU), Bihar, Pusa (Samastipur)

Yield Net return

(t/ha) ($/ha) Yield Net return Yield Net return (t/ha) ($/ha) (t/ha) ($/ha)

848125, India Rice - wheat - 7.9 343.4 8.2 360.7 8.7 377.6

Rice . winter maize 8.7 360.2 9.4 395.2 9.9 409.8

Rice - potato - 12.6 409.9 - black gram

14.5 519.2 15.2 544.1

Rice - Indian 6.9 283.5 7.7 322.3 8.2 343.0 mustard - green gram

green gram

green gram

Rice - gram - 7.0 290.9 7.4 306.8 7.6 315.7 green gram

Yield Net profit

SEM ± CD (0.05) SEM ± CD (0.05)

Irrigation (I) at same 0.1 0.3 6.8 18.9 level of cropping sequence (C)

C at same level of I 0.1 0.4 8.7 24.3

a Av of 6 yr.

irrigation water was kept at 7 cm 3 d after and summer irrigation in the main plots disappearance of ponded water. and cropping sequence in the subplots,

The experiment was laid out in a split- replicated three times. Irrigation sched- plot design with a combination of winter ules and amounts for each crop were

Table 1. Irrigation schedules and amounts for each crop of different sequences. Bihar, India. 1986-91.

Indian Green gram and Wheat Maize Potato mustard Gram black gram

Irrigation level Schedule Amount Schedule Amount Schedule Amount Schedule Amount Schedule Amount Schedule Amount

(IW:CPE) a (cm) (IW:CPE) (cm) (IW:CPE) (cm) (DAS) b (cm) (DAS) (cm) (DAS) (cm)

Suboptimal 0.5 12 0.5 18 0.6 12 Rainfed 0 Rainfed 0 Rainfed 0 Optimal 0.7 18 0.7 24 0.9 12 60 6 45 6 30 6 Supraoptimal 0.9 24 0.9 30 1.2 18 30, 60 12 45, 75 12 20,40 12

a IW:CPE = irrigation water depth - cumulative pan evaporation ratio. b DAS = days after sowing.

26 IRRN 19:1 (March 1994)

An improved protocol for nonradioactive DNA analysis using digoxigenin labeling

determined (Table 1). Optimum levels were based on regression lines developed at the site using 6-7 irrigation levels. (In a regression line, a point above optimum was termed supraoptimum; a point below, suboptimum.)

The soil is a sandy loam calcareous (23% CaCO 3 ) with pH of 8.4 (1:2 soil:water), developed from silty allu- vium sediments with EC less than 0.6 dS/ m. The water table was 2.0-6.1 m from the surface. Soil sampled from 0-30 cm contained 275 kg N/ha, 21.5 kg P/ha, and 83 kg K/ha.

Variation in irrigation levels and cropping sequences caused significant

differences in yield. The interaction between irrigation and cropping sequence was also significant. At each irrigation level, rice - potato - green gram yielded the most, followed by rice - winter maize - black gram. At the suboptimal and optimal levels, yields did not differ significantly between sequences contain- ing mustard and gram. At the supraoptimal level, gram had a signifi- cant decrease in yield compared with mustard because gram does not respond to more frequent irrigation (Table 2).

tion level and cropping sequence was significant, as was the interaction effect

Variation in net return due to irriga-

Research methodology DNA labeling by random priming.

Probe DNA template is denatured for 10 min in a boiling water bath and chilled immediately on ice. The following are

R. Mauleon, R. Scott, and R. Nelson, IRRI then added to every 10 µl of template

We report here a simplified protocol for primer mix (random hexanucleotides, detecting membrane-bound DNA based

and 2 mg/ml bovine serum albumin), steroid which occurs naturally only in MgC1 2 , 0.1 M; dithioerythritol, 1 mM; on digoxigenin (DIG) labeling. DIG is a 62.5 U/ml; Tris-HCl, 0.5 M (pH 7.2);

digitalis plants ( Digitaria lunata and D. 2 µl 10X dNTP mix (dATP, 1 mM; purpurea ). The possibility of contaminat- dCTP, 1 mM; dGTP, 1 mM: dTTP, ing most biological samples with DIG- 0.65 mM; and DIG-11-dUTP, 0.35 mM), containing compounds is, therefore, 5 µl sterile distilled water, and 1 µl minimal. In this procedure, the DIG- Klenow enzyme (2 U/µl). The resulting labeled DNA is hybridized to the target

sodium acetate, and 100 µl of cold DIG-labeled probe. The physical location µl of tRNA (2 mg/ml), 3.5 µl of 3 M alkaline phosphatase is bound to the labeled probe is precipitated by adding 10 an anti-DIG antibody conjugated to adding 2 µl of 0.2 M EDTA (pH 8). The detected in a two-step procedure, where at 37 °C. The reaction is stopped by DNA. The labeled DNA hybrid is then mixture is incubated for 2 h to overnight

of the hybrids is then determined by absolute ethanol. The addition of tRNA is using chromogenic or luminescent optional but beneficial if labeling a small substrates for alkaline phosphatase. amount of DNA. The labeled DNA is

DNA labeling with 70% ethanol, vacuum-dried, and DIG is purchased as a labeled DNA resuspended in 200 µl TE-SDS (Tris- precursor, DIG-11-dUTP (Boehringer HCl, pH 8, 10 mM; EDTA, 1 mM; SDS, Mannheim). This can be incorporated 0.1 %). A fifth of the reaction is added to into a probe DNA by one of three every 10-15 ml of hybridization buffer. methods: nick translation, random The rest of the probe keeps indefinitely at priming, or amplification using the 20 °C. polymerase chain reaction (PCR). Our DNA labeling using PCR ( adapted

(100 ng to 3 µg DNA): 2 µl of 10X

pelleted at 12,000 rpm for 5 min, rinsed

random priming and PCR labeling from a procedure from the International procedures are described. Maize and Wheat Improvement Center ).

between irrigation and cropping se- quence. Net return grew significantly with each increase in irrigation level for rice - potato - green gram, but for rice - winter maize - black gram, net return increased only up to the optimum irrigation level. Net returns were not significantly different between rice - wheat - green gram and rice - winter maize - black gram at the suboptimal level; at higher levels, net return was superior for the latter (Table 2).

A reaction mixture for thermal amplifica- tion is made with the following constitu- tion: distilled water, 29.6 µl; 10X Taq incubation buffer (Tris-HCl, pH 8, 100 mM; MgCl 2 , 15 mM; KCl, 500 mM; and gelatin, 1 mg/ml), 5 µl; 10X DIG-dNTP mix (dATP, dCTP, and dGTP, 2 mM each; dTTP, 1.65 mM; and DIG-dUTP, 0.35 mM), 5 µl; primer mix (1 µM each

5'-GTAAAACGACGGCCAGT-3' and of M13-20 =

M13-R= 5'-AACAGCTATGACCATG-3'), 5 µl; Taq polymerase (5 U/µl), 0.4 µl; and template DNA (1 ng/µl), 5 µl. Thermal cycling is performed using the following program: 94 °C (1 min), 1 cycle; 94 °C (1 min), 55 °C (2 min), and 72 °C (1 min), 25 cycles; and 72 °C (1 min), 1 cycle. The amplified product is precipitated by adding 5 µl of 3 M sodium acetate and 100 µl of chilled absolute ethanol, rinsed with 70% ethanol, vacuum-dried, and resuspended in 50 µl of TE (Tri-HCl, pH 8, 10 mM; and EDTA, 1 mM). Typical yield is 2.5 µg. The M13 primers work for sequences cloned in pUC, pGEM, and pBluescript plasmids.

Hybridization and washing The choice of blotting membrane is extremely important. We have had best results with positively charged nylon membrane (Hybond N + , Amersham). The

IRRN 19:1 (March 1994) 27

membrane is manipulated with utmost care and is only handled at the edges with forceps. The following is our procedure for hybridizing probes to DNA trans- ferred on Hybond-N + .

Blots are hybridized at 68 °C over- night in plastic boxes or sealed plastic bags using the following hybridization solution: 5X SSC; dried skim milk, 0.5%; sarcosyl, 0.1 %; SDS, 0.02%; and salmon sperm DNA, 100 µg/ml. Blots are pre- hybridized initially for at least an hour in the solution without the probe. About 2.5 ml of probe-containing hybridization solution is used per 100-cm2 blot. Probes are denatured by boiling for 15 min in a water bath prior to addition to the hybridization solution. After hybridiza- tion, the following stringency washes are performed: twice for 5 min at room temperature with 2X SSC, 0.1 % SDS; and twice for 15 min at 68 °C with 0.1X SSC, 0.1 % SDS. The prehybridization and probe-containing hybridization solution may be kept at -20 °C and reused several times. The probe should be denatured, however, by boiling the solution in a water bath for 15 min before use.

Detection of hybrids Chromogenic method. The following incubations for detection of probe- hybrids are performed at room tempera- ture. The blot is washed for 1 min with buffer 1 (Tris-HCl, pH 7.5, 100 mM; and 150 mM NaCl) and incubated in buffer 2 (buffer 1 with 100 µg/ml sheared salmon sperm DNA and 2% dried skim milk or casein, or 0.5% blocking reagent [Boehringer Mannheim]) for 30 min. Buffer 2 is replaced with buffer 1 containing 1.50 mU/ml anti-DIG alkaline phosphatase conjugate (anti-DIG-AP [Boehringer Mannheim]) and the blot is incubated for another 30 min. Unbound anti-DIG-AP is then removed by two rinses of buffer 1 (plus 0.3% Tween 20), each for 15 min. The blot is washed for 2 min in buffer 3 (Tris-HC1, pH 9.5, 100 mM; NaCl, 100 mM; and MgCl2, 50 mM) and incubated with color substrate. The color substrate is prepared by adding 45 µl NBT (nitroblue tetrazolium salt, 75 mg/ml in 70% dimethylformamide) and 35 µl BCIP

28 IRRN 19:1 (March 1994)

(toluidinium salt of 5-bromo-4-chloro-3- indolyl phosphate, 50 mg/ml in dimethyl- formamide) to 10 ml of buffer 3. Hybrid signals are visible after 1-2 h. The intensity of the signals is adjusted by shortening or prolonging the incubation of blots in the color substrate, but this is normally less than a day. After maximum strength of signals is reached, the blots are washed twice in distilled water and dried. Buffer 2 can be reused several times if kept frozen during storage. The anti-DIG-AP solution in buffer 1 may also be reused if several blots have to be processed but it is only active within 12 h at 4 °C. Color blots can be reprobed, although somewhat laboriously, by washing off the stain with dimethyl- formamide at 65 °C. After decolorization, the probe is stripped off by incubating the blots twice in 0.4 M NaOH for 15 min at 45 °C. Blots are then rinsed with water and washed twice for 5 min with 2X SSC

Nonradioactive DNA analysis using biotin labeling and chemiluminescent detection C. M. Vera Cruz, Plant Pathology Depart- ment, Kansas State University (KSU), Manhattan, Kansas; A. K. Raymundo, Institute of Biological Sciences, University of the Philippines at Los Baños, Philippines; and J. E. Leach, KSU, Kansas, USA

The most common method for detecting DNA in blots involves using radioac- tively labeled probes. Technical advances in nonradioactive detection methodolo- gies have made these attractive alterna- tives. The reagents for nonradioactive DNA analysis are relatively stable (the half-life of the most commonly used radioisotope, 32 P, is 14 d). Using non- radioactive labeling reduces the fre- quency of shipping perishable and hazardous materials. Using nonradio- active probes eliminates exposure to radioactive materials and disposal of radioactive waste. Additionally, labeled probes are stable for at least several months.

Several types of labeling and detection kits are available commercially. They vary in molecules used for labeling DNA (the ligand) and the labeling and detec-

at room temperature. The blots may be stored dry or used directly for reprobing.

Luminescent method. This is the method of choice for blots that require frequent reprobing and is based on the emission of light during the dephos- phorylation of AMPPD (3-[2'-spiro- adamantane]-4-methoxy-4-[3'-phos- phoryloxy]-phenyl-l,2-dioxetane). This procedure is similar to the chromogenic technique except that the substrate solution contains AMPPD instead (100 µg/ml AMPPD in buffer 3). Blots in AMPPD solutions are wrapped neatly in clingfilm. X-ray film is exposed to these blots for 15 min or more (depending on the intensity of signals). Multiple expo- sures are possible since the light emission persists for 24 h. The AMPPD solution in buffer 3 can be reused up to five times within 2 mo of preparation. Probes are stripped in a manner similar to that in the chromogenic method.

tion methods. The biotin-avidin system is one of the most widely used nonradio- active labeling methods. Biotin is incorporated into the probe DNA as biotin- 11 -dUTP. Subsequently, avidin conjugated to alkaline phosphatase is bound to the biotin. The complex is detected using a chemiluminescent substrate for alkaline phosphatase (AMPPD, 3-[2'-spiroadamantane]-4- methoxy-4-[3'-phosphoryloxy]-phenyl-1, 2-dioxetane). A simplified protocol based on the biotin-avidin system follows.

DNA labeling and detection Biotin, purchased as biotin-11-dUTP, is substituted for dTTP in labeling reac- tions. The biotin can be incorporated into the DNA probe by nick translation, random priming, or amplification using polymerase chain reaction (PCR). Commercially prepared kits are available for each of these methods. The protocols for labeling and detection described here have been used with kits from Tropix (47 Wiggins Ave., Bedford, Massachusetts 01730, USA).

DNA labeling using nick translation. Add the following to a microcentrifuge tube: 10 µ1 of DNA sample containing 0.03-2 µg DNA, 3 µl of dNTP mixture,

1 µl of biotin-11-dUTP, 2 µl of buffer concentrate, 2 µl of sterile distilled water, and 2 µl of enzyme mix. Mix by repeated pipetting. Centrifuge for a few seconds. Incubate tube for 30-60 min at 15 °C. Add composition or heat at 65 °C for 10 min to stop reaction. The labeled probe can be used without further purification.

Hybridization and washing Hybridization. Prehybridize blot in a plastic bag or box with sufficient hybridization solution to cover it (Table 1). Incubate for 6 h at 65 °C without shaking. Denature the labeled probe by boiling for 10 min. If desired, include labeled marker DNA corre- sponding to size standard on blot. Add denatured probe directly to hybridiza- tion solution. Mix and reincubate for 6-14 h at 65 °C with gentle shaking. Store hybridization solution at -20 °C for future use.

Washing of blots. Wash blots twice with wash solution 1 for 5 min each time at 65 °C with gentle shaking and then twice with wash solution 2 for 15 min under the same conditions. (See Table 2 for preparation of wash solu- tions.)

Signal detection by the AMPPD method All steps are done with gentle shaking at room temperature. Wash blots briefly in 1X SSC. Wash blots in blocking buffer twice for 5 min and once for at least 20 min. (Blocking buffer is prepared by adding 0.1% Tween 20 [polyoxy- ethylene sorbitan monolaurate] to 1X conjugate buffer [stir 1 % dried skim milk or casein into 1X phosphate buffered saline (PBS) (Table 2) and microwave for 45 s or dissolve under low heat and mix].) Blots can be left overnight at this point. Cover the blot with 10 ml of the AVIDx-AP conjugate buffer and incubate for 30 min. (AVIDx-AP conjugate buffer [1:10000] is prepared by spinning AVIDx-AP conjugate for 4 min and then adding 1 µl supernatant to 10 ml conjugate buffer.) Adjust amount so that blot is submerged, about 10 ml/100 cm 2 blot. Wash blots once in blocking buffer for

Table 1. Hybridization solution.

Amount Solution Stock

ml/50 ml ml/100 ml

1 mM EDTA 0.5 M EDTA 0.1 0.2 7% SDS 20% SDS 17.5 35.0 0.25 M disodium 0.5 M 25.0 50.0

Boiled salmon sperm 10 mg/ml 1.5 3.0 phosphate, pH 7.2

DNA, 300 µg/ml a

a 10 mg/ml salmon sperm DNA in distilled water. Autoclave twice, aliquot, and store at -20 °C. (Herring sperm DNA is an alternative to salmon sperm DNA.)

Table 2. Solutions for detection of biotin-labeled DNA.

Amount Stock (m1/100 ml)

Solution SSC SDS SSC SDS

2X SSC, 1.0% SDS (Solutlon 1) 20X 20% 10 5 0.1X SSC, 1.0% SDS (Solution 2) 20X 20% 0.5 5 1x SSC 20X 5

10X phosphate buffered saline a

0.58 M Na 2 HPO 4 0.17 M NaH 2 PO 4 0.68 M NaCl

1000 ml 82.3 g Na 2 HPO 4 23.5 g NaH 2 PO 4 H 2 O 40.0 g NaCl

a Mix Na 2 HPO 4 in 500 ml in small amounts at low heat to dissolve completely. Add NaH 2 PO 4 •H 4 O in small amounts until completely dissolved. Add NaCI: dissolve completely (pH 8.2: 1X solution is about pH 7.3-7.4).

10 min. Wash in wash buffer four times for 5 min, and with assay buffer twice for 5 min. (Wash buffer is prepared by adding 0.3% Tween 20 to 1X PBS. Assay buffer is prepared by using 0.1 M diethanolamine [if solid, liquefy at 37 °C], 0.96 m1/100 ml and 1 mM MgCl 2 , [stock is 0.5 M], 0.20 m1/100 ml.)

Incubate blots singly in AMPPD solution (50 µg/ml in assay buffer) for 5 min. Store used AMPPD solution at 4 °C; it can be reused at least eight times. Remove excess solution from blot by laying it briefly on a paper towel. Wrap the blots in plastic wrap and arrange in an X-ray cassette. In the dark room, place a film on the blots in the cassette and expose it for a 30-min test exposure. Develop the film. Expose for a longer or shorter period if needed. Luminescence continues for at least 24 h.

rapidly for 5 min at room temperature. Repeat twice. Wash blots twice for 5 min with 1X SSC at room temperature and air-dry or store wet in plastic wrap at 4 °C.

Reprobing Keep blot moist in plastic wrap if it is to be reprobed. Heat 1X SSC with 1% SDS to 95 °C. Pour over the blot and agitate

IRRN 19:1 (March 1994) 29

IRRN REMINDER

Reprint service. All items included in the Rice literature update are available

at the IRRI Library and Documentaion Service. Photocopies of original documents (not to exceed 50 pages) are supplied free to rice scientists of developing countries. Rice scientists elsewhere are charged US$0.20 for each page or part of a page copied, plus postage. Make checks or money orders payable to Library and Documentaion

Service, IRRI. Address requests to Library and

Documentation Service, IRRI, P.O. Box 933, Manila 1099, Philippines. Fax: (63-2) 818-2087, electronic mail:

IN%"C. AUSTRIA@.CGNET.COM"

Aseptic mass collection of anthers for increasing effi- ciency of anther culture in rice breeding H. P. Moon, K. H. Kang, and S. Y. Cho, Rice Breeding Division, Crop Experiment Station, Rural Development Administration, Suwon 441-100, Korea

Anther culture is widely used in rice varietal improvement programs in Korea. The first anther-derived rice cultivar, Hwaseongbyeo, was developed in 1985. Five more have been developed since: Hwacheongbyeo, Hwajinbyeo, Hwaryeongbyeo, Joryeongbyeo, and Hwaseonchalbyeo. These cultivars are being grown on more than 10% of the

Comparison of anther-plating efficiency and anther culture response between vacuum collection and the conventional method used in rice anther culture. a

a) The assembled apparatus for aseptic mass collection of anthers consists of a vacuum source and an aseptic anther- collecting part; b) close-up of the anther-collecting part, made of a stainless steel cylinder body, 10- ml tube, and extracting tip.

rice area in Korea. Anther plating Anther culture response

increased callus induction and plant collecting Anthers Time Time/100 Callusing Plant regenerationb

regeneration, thus increasing the effi- ciency of anther culture breeding. Methods normally used for extracting

time-consuming. They are not appropri- on media, however, are laborious and

Conventional 1743 601 34.5 303 17.4 364 20.5 anthers from rice florets and placing them Vacuum 5980 592 9.9 1046 17.5 2224 40.5

regenerated plants. b Plant regeneration (%) = ate for breeding programs requiring many

Recent advances have resulted in Anther-

method plated elapsed anthers (no.) (min) (min) no. % no. %

a Mean of 6 replications with 5 japonica genotypes.

No. of plants regenerated No. of anthers plated

× 100.

We devised a simple apparatus for aseptic mass collection of anthers. Assembled, it consists of a vacuum source (Fig. la) and an aseptic anther- collecting part, made up of a stainless steel cylinder body, 10-ml tube, and extracting glass pipet-tip (Fig. 1b). After being autoclaved, it is used directly in the assembled apparatus.

stage (uninucleate-binucleate) are clipped and then sucked up by the vacuum with power pressure of 14-20 mm Hg. The collected anthers are immediately transferred from the tube to callus induction medium with a sterilized spatula or forceps in a laminar flow cabinet or clean benches.

We conducted a simple test that showed the anther-plating efficiency of vacuum-collecting to be three times more efficient than that of the conventional method. It took 592 min to plate 5,980 anthers on callus medium with vacuum collection and 601 min to plate 1,743 anthers using the conventional method (see table).

Rice florets with anthers at the proper

Frequency of callus induction from anthers was similar for both methods. Plant regeneration rate and absolute number of plantlets were far greater using the vacuum-collecting method (see table). Possible damage and desiccation of immature anthers from suction did not harm anther culturability.

With the vacuum-collecting method,

Polymerase chain reaction amplification of DNA from bacterial pathogens of rice using specific oligonucleotide primers B. Cottyn, A. T. Bautista, and R J. Nelson, IRRI; J. E. Leach, Plant Pathology Depart- ment, Kansas State University, USA, J. Swings, Laboratory of Microbiology, Rijks Universiteit Gent, Belgium. and T. W. Mew, IRRI

The polymerase chain reaction (PCR) is a powerful molecular technique that allows a segment of DNA to be amplified more than a millionfold even when the tem-

large amounts of anthers can be gathered quickly and easily, with reduced contami- nation during collection and plating. This method can enhance efficiency, particu- larly when sampling large breeding populations. It can also be useful in pollen culture where many isolated pollens are needed for culturing and in in vitro selection at haploid level.

plate DNA is present in a very tiny amount. The technique involves cycles of denaturation of duplex template DNA, annealing of two oligonucleotide primers to specific regions in the DNA, and extension of the region flanked by the two primers. This process results in an exponential increase in copy number of the flanked region, permitting specific DNA sequences to be detected with extraordinary sensitivity. Thus PCR can provide a useful diagnostic technique when a high degree of sensitivity is required.

We investigated the possibility of amplifying DNA from bacterial patho-

30 IRRN 19:1 (March 1994)

Amplification of different bacterial genomic DNA using 10 different primerpairs.

33 Xoo strains Amplification with all 10 primerpairs; banding

32 Xocola strains Amplification with 9 primerpairs; 7 primerpairs

X. campestris pv. cerealis Amplification with 5 primerpairs; all identical to X. campestris pv. graminis Xoo pattern X. campestris pv. poae

patterns all identical to each other

identical to Xoo pattern 11 reference strains of X. campestris pathovars

X. campestris pv. armoraciae X. campestris pv. citri X. campestris pv. campestris X. campestris pv. phaseoli X. campestris pv. holcicola X. campestris pv. vasculorum X. campestris pv. vesicatoria

Nonspecific amplification

5 Xanthomonas reference strains X. fragariae Amplification with 6 primerpairs; all identical

X. albilineans Nonspecific amplification X. axonopodis X. maltophilia x. populi

to Xoo pattern

22 Philippine Pseudomonas rice seed isolates Nonspecific amplification 8 Pseudomonas reference strains Nonspecific amplification

P. aeruginosa P. avenae P. fluorescens P. fuscovaginae P. glumae P. marginalis P. plantarii P. putida

(a) Location of the primers in relation to the sequence of the repeti- tive element IS1112 from Xoo. (b) Gel electrophoresis banding pattern of the different DNA fragments ampli- fied by each primerpair. Lanes 1 to 10 depict amplification by primerpairs Ad, At, Ac, Xd, Bd, Xt, Av. Bt, Xc, and Bc, respectively, of plasmid DNA containing the repetitive element IS1112. Lanes 11 and 12 depict amplification of Xoo and Xocola DNA, respectively, by primerpair Bd resulting in a double band for Xoo and a single band for Xocola. Lane 13 con- tains a molecular weight marker.

2 Philippine Erwinia rice isolates 2 Erwinia reference strains

E. herbicola E. stewartii

Nonspecific amplification Nonspecific amplification

gens of rice by using primers constructed from the repetitive DNA element IS1112 isolated from the genome of Xantho- monas oryzae pv. oryzae (Xoo), the causal organism of bacterial blight (BB) in rice. Three upstream and four down- stream 20-basepair (bp) oligonucleotide primers were commercially synthesized based on the DNA sequence of elements IS1112. The upstream primers were designated with capital letters A, B, and X and the downstream primers with small letters c, d, t, and v. By combining these primers, 10 different primerpair combina- tions were formed: Ac, Ad, At, Av, Bc, Bd, Bt, Xc, Xd, and Xt. Based on the structure of IS1112, each primerpair would be expected to amplify a discrete fragment of between 96 and 797 bp (see figure).

rice pathogens and other Xanthomonas were analyzed using the primers. For DNA isolation, bacterial cultures were grown in nutrient broth to early log phase. Cells were then harvested using a centrifuge at 12,000 rpm for 10 min. The supernatant was discarded, and the cells resuspended in 2 ml of 100 mM Tris-HCl pH 8.3 and 1 mM EDTA (1 X TE). Sodium dodecylsulfate (250 µl of 10%

Different bacterial DNA samples from

IRRN 19:1 (March 1994) 31

SDS) and proteinase K (50 µl of 10 mg/ ml) were added, and tubes were incu- bated at 37°C for 1 h with gentle shaking. Then 0.45 ml of 5M NaCl was added. After thorough mixing, 0.4 ml of hexadecyltrimethylammonium bromide (CTAB) solution (10% CTAB in 0.7 m NaCl) was added, and the tubes were incubated at 65°C for 20 min. An equal volume of chloroform:isoamyl alcohol (24:l) was added. The mixture was shaken for 30 min, then centrifuged for 30 min at 15,000 rpm. The aqueous (upper) phase was transferred with a bent Pasteur pipette to a fresh tube containing an equal volume of cold isopropanol and mixed gently until the DNA had precipi- tated. This was hooked out using a bent Pasteur pipette and washed in 70% ethanol. Purified bacteria DNA was dissolved in 1X TE and stored at -20°C. Additional purified DNA samples were obtained from other sources.

approximately 20 ng of DNA as template The PCR reaction mix included

in a 50 µl-reaction volume that contained 10 mM Tris-HCl pH 8.3, 50 mM KCl, 200 M each of dNTP, 0.4 M each of primer, and 1.5 units of Taq polymerase (Perkin Elmer Cetus or Boehringer Mannheim). Amplification was per- formed on a Perkin Elmer Cetus DNA Thermocycler with an initial denaturation step at 94°C for 2 min. This was followed by 40 cycles of a denaturation step at 94°C for 1.5 min, a primer annealing step at 62°C for 2 min, and an extension step at 72°C for 2 min. An additional exten- sion step of 72°C for 5 min was per- formed after the 40th cycle. PCR products were visualized by gel electrophoresis on 2% agarose in Tris- Borate-EDTA at 2 volts per cm and staining with ethidium bromide.

Amplification was possible for DNA from all the different bacteria (see table). The bands amplified for the two closely related rice pathogens, Xoo and X.o. pv. oryzicola (Xocola), were very similar and matched the expected band sizes. The

other bacteria either showed no amplifi- cation for all 10 primerpairs or exhibited banding patterns different from the expected patterns. Banding patterns different from those expected were described as “nonspecific amplification”. One primerpair, Bd, differentiated Xoo from Xocola by amplifying a double band for Xoo and a single band for Xocola (see figure).

The results show the utility of the primers for amplification and for possible PCR detection of these rice pathogens. PCR amplification of Xoo DNA could provide an extremely sensitive method for detecting and diagnosing BB patho- gen. This method could be used without isolation and purification of the organism and might be particularly applicable for diagnosis of seedborne inoculum. It could be used also as a sensitive method for detecting Xoo in studies aimed at under- standing the ecology and epidemiology of pathogens.

News about research collaboration Computers help predict how rice blast disease will react to climate changes How will global climate change influence rice production? IRRI scientist Paul S. Teng believes some of the greatest impact will be on fungal pathogens such as those that cause rice blast, the most devastating disease in temperate and subtropical ricefields.

IRRI and the U.S. Environmental Protection Agency are cooperating to learn how climate factors-enhanced UV-B radiation, temperature, and rainfall—could change the distribution of rice blast and the damage it could cause to rice production.

Teng and his coresearcher, Luo Yong of China, are using computer simulation models to help answer their questions. They are using historical weather data of 61 locations in seven Asian countries with a model of the rice crop and a simulation of rice blast disease.

They learned that variations in rainfall did not change where blast was found nor the severity of its epidemics. On the other hand, a 1-3° C shift in mean temperature significantly changed the disease's impact, but this varied by ecological zone. In the cool subtropical zones of Japan and northern China, raising the ambient temperature increased the risk of a rice blast epidemic. In the humid tropics and subtropics, the risk became greater with lower ambient temperatures.

geographic information systems tech- nology to display these data on risk maps. The next step is to prepare maps that will help policymakers understand the issues, by graphically illustrating the potential losses that could be caused by blast under several scenarios of temperature change. This is another example of rice scientists anticipating potential problems rather than correcting damage after it occurs in farmers’ ricefields.

The IRRI scientists have used

Bangladesh and IRRI: more than 20 years of rice research collaboration The completion of the Bangladesh Rice Research Institute (BRRI)-IRRI Project marks more than two decades of highly successful collaboration between IRRI and Bangladesh. The production gains achieved during these years, the result of rice research and development programs, have helped Bangladesh become nearly self-sufficient in rice.

But the close working relationship is continuing. IRRI is keeping its liaison office in Dhaka to maintain active ties with Bangladesh's dynamic rice research program. BRRI is a participant in the Rainfed Lowland Rice Research Consor- tium, focusing on drought problems in the ecosystem.

BRRI released 24 improved rice varieties for planting by farmers in Bangladesh, making a major contribution to doubling the country’s annual produc-

32 IRRN 19:1 (March 1994)

tion to 28.5 million tons of rough rice. These varieties were also shared with other countries.

Seven IRRI scientists were posted in Bangladesh from 1971 to 1993 to work along with BRRI researchers. Through the project, 126 BRRI personnel obtained master's and doctorate degrees, doing their thesis research at IRRI.

Through the BRRI-IRRI Project, the country took part in international networks for rice genetic evaluation, soil fertility, and farming systems research. The U.S. Agency for International Development and the Canadian Interna- tional Development Agency were the major providers of financial support to the project. Other donors contributing to

its success have been the Australian International Development Assistance Bureau, the International Development Research Centre, the International Fund for Agricultural Development, and the Asian Development Bank.

GIS: a new tool for analyzing rice germplasm How do you analyze rice seeds? Scien- tists have dozens of ways, such as by their genetic traits, economic value, where they are grown, their uses, and their origin. Scientists at IRRI are now using geographic information systems (GIS) technology to aid in this work.

A global positioning system (GPS) network of navigation satellites that can be used to pinpoint a site anywhere on earth will probably become a standard tool on future germplasm-collecting explorations. In early 1993, Duncan Vaughan, then a geneticist at IRRI, used GPS for the first time in collecting wild rices in southern Africa. By recording the exact location of where he found the wild rices in Botswana and Zambia, it will be possible to relocate the same populations in the future.

GPS makes it easy to use GIS compu- ter programs to link information about a site—such as its elevation. slope, distance

from a water source, and soil—with socioeconomic factors and other data.

and GIS laboratory are mapping the locations of cultivated and wild rices in South and Southeast Asia. According to Michael T. Jackson, GRC head, this will correlate the germplasm distribution with environmental parameters and help in selecting samples for genetic comparison of diversity. Scientists in the United Kingdom at the University of Birming- ham and at the Cambridge Laboratory of the John Innes Centre, Norwich, are collaborating with the IRRI researchers in making these comparisons. They are identifying broadly diverse samples of rice to be conserved in safety duplicate collections to be maintained at other genebanks around the world. Jackson believes that being able to pinpoint the locations of origin and cultivation of rices greatly improves IRRI's efforts to conserve germplasm and to make it available to researchers worldwide.

The Genetic Resources Center (GRC)

SARP theme leadership production, crop and soil management, shifting to NARS and IRRI and crop protection. Starting this past

January, SARP had a new structure and Rice scientists have used computer scope. The focus is on practical applica- modeling for nearly a decade as one tions of modeling, including building approach to their research. Working with interactions with clients—policymakers, the Wageningen Agricultural University extensionists, and farmers. Scientific and the Centre for Agrobiological leadership is coming from national Research in the Netherlands, IRRI programs and IRRI personnel who are the scientists have been building SARP, the research theme coordinators. This change Systems Analysis and Simulation in Rice in SARP leadership is another step in Production project. Sixteen national programs taking on greater multidisciplinary SARP teams in nine research responsibilities. countries are integrating their knowledge in studies of practical problems and applying simulation and systems analysis four themes: agroecosystems, potential

Ministry in Vietnam endorses no early spray policy Farmers in Vietnam can expect to reduce their use of insecticides by at least 20% by forgoing early spraying of rice crops. The Ministry of Agriculture and Food Industry has endorsed this new integrated pest management (IPM) policy, the result of collaborative research by IRRI and Vietnamese scientists.

Currently, more than 80% of farmers in the Mekong Delta spray their rice early—within 30 days after transplanting or 40 days after direct seeding. They mistakenly believe that spraying reduces the yield losses caused by insect damage to rice leaves. Farmer participatory research in 1992 in Angiang, Tiengiang, and Cantho provinces has shown that early spraying is not necessary.

The 20% reduction in insecticides means a saving of US$15 per hectare in a season, without a loss in rice yield. Another advantage is reduced risk of brown planthopper outbreaks, which is caused in part by early application of broad-spectrum insecticides.

The research base for the new IPM policy was developed by Nguyen Thi Thu Cuc of the University of Cantho and Sam Fujisaka, Dale G. Bottrell, and K. L. Heong of IRRI.

~~

IRRN 19:1 (March 1994) 33

Announcements Postdoctoral research fellowships at IRRI The International Rice Research Institute invites applicants for postdoctoral research fellowships: Epidemiology/modeling of cultural control of rice sheath blight. The success- ful candidate will participate in a multidisciplinary research project aimed at developing the epidemiologic theory for empirical evaluation of cultural control strategies, developing computer simula- tion models of sheath blight development for integration of cultural control and cropping practices in a systems frame- work, and interfacing a sheath blight- cultural control model with rice crop growth models to estimate losses.

Candidates must have a Ph D in plant pathology or related biological science. Experience with quantitative epidemiol- ogy and modeling is essential; experience with tropical pathosystems is desirable. The appointment is for 1 year, with a possible extension to 2 years subject to performance appraisal. The position is funded by the United Nations Develop- ment Programme-World Bank.

To apply, send curriculum vitae, university transcripts, and three letters of

recommendation to P. S. Teng, plant pathologist, Entomology and Plant Pathology Division, IRRI.

Soil microbiology. The successful candi- date will work on a Danish International Development Agency-funded research project seeking to assess the opportunities for symbiotic nitrogen fixation in rice. The objective is to identify and improve existing or novel associations between rice and nitrogen-fixing bacteria and to assess the metabolic potential of rice for nodulation.

Applicants should have a Ph D in soil microbiology or related discipline in the areas of microbial ecology, rhizobiology, or biological nitrogen fixation. Training or experience in cellular and molecular . biology is advantageous. The position is for a period of up to 3 years and is available immediately. It will remain open until a satisfactory candidate is identified.

Send curriculum vitae, availability date, names and addresses of three references (with telephone and fax numbers) to J. K. Ladha, soil microbiologist, Soil and Water Sciences Division, IRRI.

Plant breeding—rainfed lowland rice. The successful candidate will work on identi-

fying genes controlling root system development in rice. The work involves developing a marker-aided selection scheme for deep roots, collaborating in studies on root morphology of cultivars adapted to drought-prone environments, and assisting in screening of breeding materials.

Candidates must have a Ph D in plant breeding or related field. Experience in molecular genetics is preferable, experi- ence in rice is desirable. Applicants must be fluent in English.

at Ubon Rice Research Center, Ubon, Thailand. The appointment will initially be for 2 years and is available immedi- ately. It will remain open until a satisfac- tory candidate is identified. The position is supported by a grant from the Rockefeller Foundation.

Research will be conducted at IRRI and

Send curriculum vitae, university transcripts, and three letters of recommen- dation to S. Sarkarung, plant breeder, IRRI, Rice Research Institute Building, Department of Agriculture, P. 0. Box 9- 159, Bangkok 10900, Thailand, Fax: (66- 2) 561-4894, or N. Huang, plant molecular geneticist, Plant Breeding, Genetics, and Biochemistry Division, IRRI.

Tropical agriculture conference

The Faculty of Agriculture of the University of the West Indies is sponsor- ing a conference on Advances in Tropical Agriculture in the 20th Century and Prospects for the 21st Century: TA 2000. The conference will be held from 4 to 9 September in Port-of-Spain, Trinidad.

The conference program will record advances in tropical agricultural develop- ment in the 20th century, trace their genesis in applied policy, management and technology, and evaluate prospects and strategies for further advances in the 21 st century. Specific objectives include reviewing tropical agriculture from around the world, examining advances made in the 20th century in crop and

livestock production, soil and land management. economic and social issues in agricultural development. and provid- ing for the scholarly exchange on advances, successes, and prospects for tropical agriculture in the 21 st century.

Send requests for details to the Secretariat, TA 2000, Office of the University Dean, Faculty of Agriculture, University of the West Indies, St. Augustine, Trinidad, West Indies. Tel: (809) 662-2686. Fax: (809) 662-1182.

New IRRI publications New publication Modelling crop-weed inter-actions The 1994 information please environ-

Grain quality evaluation of world rices Hammond. Order from World Resources

IRRI 1992-1993: rice in crucial envinron- Hampden Station, Baltimore, MD 21211, ments USA.

mental almanac. Edited by Allen

Institute Publications, P. O. Box 4852,

34 IRRN 19:1 (March 1994)

IRRI extends deadline for • two of the nominee’s published Nominations and reference letters nominating young women papers or technical reports issued during should be sent to

scientists for 1994 award 1989-93, Chairperson • curriculum vitae or biodata state- Outstanding Young Women

Young women in rice science from China ment, with certificate of birthdate (born in Rice Science Award to Burundi have already been nominated for the 1994 Outstanding Young Women in Rice Science Award.

This is the foremost international recognition to honor young women working in developing countries whose scientific research is making significant contributions to rice productivity. It is sponsored by IRRI and DANIDA, the Danish International Development Agency.

receiving nominations to 1 June, rather than 1 February. The original deadline had been set so the awardees could be part of the International Rice Research Confer- ence (IRRC) that was planned for April. Since there will not be an IRRC this year, the 1994 winners will come to IRRI in September to present seminars on their research projects and to receive their awards.

IRRI has extended the deadline for

Other additions have been made to the competition to motivate research agencies

women in rice research and promote their professional improvement. Each of the five regional winners will receive US$1,000 to further her research as well as a plaque and a travel grant to visit IRRI. Every woman nominated for the 1994 award will be presented a certificate of achievement.

The new chair of the awards committee is Gelia Castillo, eminent rural sociologist of the University of the Philippines at Los Baños.

Extending the deadline to 1 June will allow even more young scientists to be nominated by their institutions. One award will be made for each of the five major rice-producing regions of the developing world: Africa, South Asia, West Asia, Southeast Asia, and Latin America and the Caribbean.

Each nomination should include • a nomination description, in not more

than 1,000 words, of the nominee's current rice research work and previous

to encourage greater participation by

accomplishments,

since 1 Jan 1954), c/o Information Center • five copies of a current photograph, IRRI.

and Complete details on the 1994 pro- • recommendations from three gram, including how to prepare a

references to support the nomination. nomination, are available by writing to this address or by sending a fax message to (632) 828-2087.

Rice dateline 18 Apr-8 May SARP Mega Workshop, IRRI ............................. M. J. Kroppf, IRRI

19-21 Apr Korea-IRRI Planning Meeting, IRRI ................................................ N. K. Park/B. S. Vergara, IRRI

4-7 May Vietnam Rice Research Conference, Hanoi, Vietnam ............................. D. W. Puckridge/F. A. Bernardo/

G. L. Denning, IRRI

10-13 May IRRI-UNIFEM Workshop on Enhancing the Incomes of Rural Women Through Engineered Systems, IRRI .................... G. R. Quick, IRRI

11-12 May China-IRRI Planning Meeting, China .............. B. S. Vergara, IRRI

16-20 May 7th Annual Meeting of the Rockefeller Foundation International Program on Rice Biotechnology, Bali, Indonesia ..................................................... G. S. Khush, IRRI

30 May-2 Jun Are Insecticides Necessary in Tropical Rice?, IRRI ........................................... K. L. Heong, IRRI

30 May-4 Jun Constraints, Opportunities, and Innovations for Wet Seeded Rice, Bangkok, Thailand .................................................. K. Moody, IRRI

20-24 Jun Clean Seed for Pest Management/ Crop Protection, Thailand ..................................... T. W. Mew, IRRI

Call for news IRRI address Individuals, institutions. and organiza- tions are invited to tell readers about upcoming events in rice research or related fields in the Rice Dateline. Send announcements to the Editor, Interna- tional Rice Research Notes, IRRI.

International Rice Research Institute P.O. Box 933 Manila 1099 Philippines Tel: (63-2) 818-1926 Fax: (63-2) 8 18-2087 Telex: (ITT) 40890 RICE PM E-mail: IN%“postmaster@CGNET.COM”

IRRN 19:1 (March 1994) 35

IRRI group for 1994

training courses

IRRI will conduct 14 short-term group training courses for 1994.

IRRI provides a limited number of scholarships for participation in these courses. To be considered for an IRRI- funded scholarship, a scientist must be affiliated with a national institution that has an official collaborative agreement with IRRI in rice-related research and training projects. A scientist interested in an IRRI-funded scholarship should apply directly to his or her institution and not to IRRI.

IRRI also accepts scientists from other institutions and agencies for the courses if they are working in rice or rice-related areas. Their applications to participate in courses must be endorsed to IRRI by their employers and specify funding sources to cover costs. IRRI’s group course training fee is approximately US$1,200/month; this does not include a participant’s roundtrip international airfare, enroute expenses, or shipping allowance upon return home.

The courses are conducted at IRRI headquarters unless otherwise indicated. For additional information, contact the Head, Training Center, IRRI.

Date Course

4 Apr-1 May Engineering for Rice Agriculture

9-25 May Training Course for Collaboration of the IRRI-UNDP-GEF International Research Program on Methane Emission from Ricefields

6 Jun-1 Jul Training on Video Production

18 Jul-9 Sep Integrated Pest Management (University of the Philippines at Los Baños/National Crop Protection Center)

25 Jul-16 Sep Integrated Nutrient Management

3 Oct-4 Nov Rice Seed Health

10 Oct-2 Dec Rice Production Research (Pathum Thani Rice Research Center, Thailand)

17 Oct-4 Nov Upland Rice Breeding

31 Oct-11 Nov Scientific Programming

4-25 Nov Research Management

14-25 Nov Gender Analysis

Rice literature update reprint service

Photocopies of items listed in the Rice literuture update are available from the IRRI Library and Documentation Service. Reprints of original documents (not to exceed 40 pages) are supplied free to rice scientists of developing countries. Rice scientists elsewhere are charged US$0.20 for each page or part of a page copied, plus postage. Make checks or money orders payable to Library and Documentation Service, IRRI.

Address requests to Library and Documentation Service, IRRI. E-mail: IN%“C.AUSTRIA@CGNET.COM”

36 IRRN 19:1 (March 1994)

Instructions for contributors

NOTES IRRN categories. Specify the category in which the note

General criteria. Scientific being submitted should appear. notes submitted to the IRRN for Write the category in the upper possible publication should right-hand corner of the first • be original work, page of the note. • have international or pan- national relevance, GERMPLASM IMPROVEMENT • be conducted during the genetic resources immediate past three years or genetics be work in progress, breeding methods • have rice environment yield potential relevance, grain quality • advance rice knowledge, pest resistance • use appropriate research diseases design and data collection Insects methodology, other pests • report pertinent. adequate stress tolerance data, drought • apply appropriate statistical excess water analysis, and adverse temperature • reach supportable conclu- adverse soils sions. other stresses

Routine research. Reports of ment

Fertilizer, cropping methods, rainfed lowland and other routine observations upland using standard methodologies flood-prone (deepwater to establish local recom- and tidal wetlands) mendations are not ordinarily seed technology accepted. Examples are single- season, single-trial field CROP AND RESOURCE experiments. Field trials should MANAGEMENT be repeated across more than soils one season, in multiple soil microbiology seasons, or in more than one physiology and plant nutrition location as appropriate. All fertilizer management experiments should Include inorganic sources replications and an internation- organic sources ally known check or control crop management treatment. integrated pest management

Multiple submissions. Insects Normally, only one report for a weeds single experiment will be other pests accepted. Two or more items water management about the same work submitted farming systems at the same time will be farm machinery returned for merging. Submit- postharvest technology ting at different times multiple economic analysis notes from the same experi- mentis highly inappropriate. ENVIRONMENT Detection Will result in the SOCIOECONOMIC IMPACT

integrated germplasm improve-

screening trials of varieties, irrigated

diseases

rejection of all submissions on EDUCATION AND COMMUNI- that research. CATION

RESEARCH METHODOLOGY

Manuscript preparation. Arrange the note as a brief statement of research objec- tives, a short description of project design, and a succinct discussion of results. Relate results to the objectives. Do not Include abstracts. Do not cite references or Include a bibliog- raphy. Restrain acknowledg- ments

Manuscripts must be in English. Limit each note to no more than two pages of double- spaced typewritten text. Submit the original manuscript and a duplicate, each with a clear copy of all tables and figures. Authors should retain a copy of the note and of all tables and figures.

Apply these rules, as appropriate, in the note: • Specify the rice production ecosystems as irrigated, rainfed lowland, upland, deepwater, and tidal wetlands. • Indicate the type of rice culture (transplanted, wet seeded, dry seeded). • If local terms for seasons are used, define them by character- istic weather (wet season, dry season, monsoon) and by months. • Use standard, internationally recognized terms to describe rice plant parts, growth stages, and management practices. Do not use local names. • Provide genetlc background for new varieties or breeding lines. • For soil nutrient studies, Include a standard soil profile description, classification, and relevant soil properties. • Provide scientific names for diseases, Insects, weeds, and crop plants. Do not use common names or local names alone. • Quantify survey data, such as infection percentage, degree of severity, and sampling base • When evaluating susceptibil- ity, resistance, and tolerance, report the actual quantification

of damage due to stress, which was used to assess level or incidence. Specify the mea- surements used • Use generic names, not trade names, for all chemicals. • Use International measure- ments. Do not use local units of measure. Express yield data in metric tons per hectare (t/ha) for field studies and in grams per pot (g/pot) for small-scale studies • Express all economic data in terms of the US$. Do not use local monetary units. Economic information should be pre- sented at the exchange rate US$:local currency at the time data were collected. • When using acronyms or abbreviations, write the name in full on first mention, followed by the acronym or abbreviation in parentheses. Use the abbreviation thereafter. • Define any nonstandard abbreviations or symbols used in tables or figures in a footnote, caption, or legend.

Tables and figures. Each note can have no more than two tables and/or figures (graphs, illustrations, or photos). All tables and figures must be referred to in the text; they should be grouped at the end of the note, each on a separate page. Tables and figures must have clear titles that adequately explain the contents.

Review of notes. The IRRN editor will send an acknowledg- ment card when a note IS received. An IRRI scientist, selected by the editor, reviews each note. Reviewer names are not disclosed. Depending on the reviewer’s report, a note will be accepted for publication, rejected, or returned to the author(s) for revision.

(continued on back cover)