25.1/2000

International Rice Reasearch Notes

Copyright International Rice Research Institute 2000

International Rice Research Institute IRRI home page: http://www.cgiar.org/irri Riceweb: http://www.riceweb.org Riceworld: http://www.riceworld.org IRRI Library: http://ricelib.irri.cgiar.org IRRN: http://irriwww/IRRIHome/irrn.htm http://www.cgiar.org/irri/irrn.htm

The International Rice Research Notes (IRRN) expedites communication among scientists concerned with the development of improved technology for rice and rice-based systems. The IRRN is a mechanism 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 three times a year in April, August, and December by the International Rice Research Institute.

About the cover Indonesian scientists are trained on how to use the chlorophyll meter in Sukamandi, Java.

Inset: Chlorophyll (SPAD) meter for need-based, real-time nitrogen management in rice. Cover photos: V. Balasubramanian

Editorial Board Michael Cohen (pest science and management), Editor-in-Chief Zhikang Li (plant breeding; molecular and cell biology) David Dawe (socioeconomics; agricultural engineering) Bas Bouman (soil, nutrient, and water management; environment) Bao-Rong Lu (genetic resources) Shaobing Peng (crop management and physiology)

Production Team Katherine Lopez, Managing Editor Editorial Bill Hardy and Tess Rola Design and layout CPS design team, Grant Leceta, and Arleen Rivera Artwork Juan Lazaro and Emmanuel Panisales Word processing Arleen Rivera

Contents4MINI REVIEW Adaptation of the chlorophyll meter (SPAD) technology for real-time N management in rice: a reviewV. Balasubramanian, A.C. Morales, R.T. Cruz, T.M. Thiyagarajan, R. Nagarajan, M. Babu, S. Abdulrachman, and L.H. Hai

RESEARCH NOTESPlant breeding

9 Evaluation of anther culture-derived linesunder upland conditions for the North Eastern Hill of IndiaA. Pattanayak and H.S. Gupta

11 Performance of cold-tolerant rice lines developedthrough anther culture for mid-altitude areas of Meghalaya, IndiaA. Pattanayak, R.N. Bhuyan, H.S. Gupta, M. Sreedhar, and M.S. Prasad

10 Petei and Mocoi: two rice cultivars developedthrough anther culture in ArgentinaM.A. Marassi, J.J. Marassi, J.E. Marassi, and L.A. Mroginski

12 Reactions to an inferred resistance of Indian andBangladesh rice varieties to bacterial blightK.S. Lee, E.R. Angeles, and G.S. Khush

2

April 2000

Pest science & management

14 Effect of variety and sowing date on false smutincidence in upland rice in Edo State, NigeriaM.O. Ahonsi, A.A. Adeoti, I.D. Erinle, M.D. Alegbejo, B.N. Singh, and A.A. Sy

17 Pathogenicity of cyst nematode, Heteroderasacchari, on rice in sand and clay soilD.L. Coyne and R.A. Plowright

18 A simple method for evaluating the virulence 15 Stem borer species compositionin Tamil Nadu, IndiaJ.C. Ragini, D. Thangaraju, and P.M.M. David

of the brown planthopperK. Tanaka

20 Hymenopteran diversity in single- and double16 An integrated approach to managingrice stem nematodesS. Chakraborti

cropped rice ecosystems in Kerala, IndiaS. Pathummal Beevi, K.R. Lyla, and T.C. Narendran

Soil, nutrient, & water management

22 Comparative efficiency of N managementpractices on rainfed lowland rice in Batac, PhilippinesA.C. Morales, E.O. Agustin, M.P. Lucas, T.F. Marcos, D.A. Culanay, and V. Balasubramanian

27 Evaluation of N management practices forirrigated transplanted rice in Pondicherry, IndiaR. Balasubramanian, S. Ramesh, D. Maniamran, S. Anbumani, B. Vijayalakshmi, D. Tiroutchelvame, and R.S.S. Hopper

23 Assessing genotypic variation in N requirementsof rice with a chlorophyll meterT.M. Thiyagarajan, S. Aruna Geetha, and V. Balasubramanian

28 Polymer-coated urea: an efficient controlledrelease N source for irrigated transplanted riceT.M. Thiyagarajan, S. Aruna Geetha, Mir Zamman Hussain, P. Saradha, P. Janaki, and V. Balasubramanian

24 Effect of planting density on chlorophyll meterbased N management in transplanted riceP. Janaki, T.M. Thiyagarajan, V. Balasubramanian

Crop management & physiology

30 Control of red rice seed banks under differentlowland management systemsLuis Antonio de Avila and Enio Marchezan

31 Identifying and grading limiting factors of uplandrice yields in farmers fields of northern ThailandK. Van Keer, G. Trbuil, and Eric Goz

34 NOTES FROM THE FIELD 37 RESEARCH HIGHLIGHTS 39

40 NEWS 47 INSTRUCTIONS TO CONTRIBUTORS

IRRN 25.1

3

MINI REVIEW

Adaptation of the chlorophyll meter (SPAD) technology for real-time N management in rice: a reviewV. Balasubramanian, A.C. Morales, IRRI; R.T. Cruz, Philippine Rice Research Institute (PhilRice); T.M. Thiyagarajan, Tamil Nadu Agricultural University; R. Nagarajan, M. Babu, Soil and Water Management Research Institute (SWMRI), India; S. Abdulrachman, Research Institute for Rice, Indonesia; and L.H. Hai, Ministry of Agriculture and Rural Development (MARD),Vietnam E-mail: v.bala@cgiar.org

lanket or package fertilizer recommendations over large areas are not efficient because indigenous nutrient supply varies widely among rice fields in Asia (Dobermann and White 1999, Olk et al 1999). Rice crops thus require different amounts of nutrients in different fields, depending on native nutrient supply and crop demand. Farmers will benefit significantly if they can adjust N inputs to actual crop conditions and nutrient requirements. The chlorophyll meter can be used to monitor plant N status in situ in the field and to determine the right time of N topdressing in rice (Peng et al 1996b, Balasubramanian et al 1999).4

B

By using this tool, we can synchronize fertilizer N application with actual crop demand. This paper reviews the development and adaptation of the chlorophyll meter technique for efficient N fertilization in rice. Chlorophyll meter The chlorophyll meter (or SPAD meter) is a simple, portable diagnostic tool that measures the greenness or relative chlorophyll content of leaves (Inada 1963, 1985, Kariya et al 1982). Meter readings are given in Minolta Company-defined SPAD (soil plantApril 2000

analysis development) values that indicate relative chlorophyll contents. There is a strong linear relationship between SPAD values and weight-based leaf N concentration (Nw), but this relationship varies with crop growth stage and/or variety (Takebe and Yoneyama 1989, Turner and Jund 1994), mostly because of leaf thickness or specific leaf weight (Peng et al 1993). The confounding effect of leaf thickness can be eliminated if foliar N concentration is expressed on a leaf-area basis. Leaf area-based N concentration (Na) has a unique linear relationship with SPAD values of rice plants at all growth stages (Peng et al 1995). The linear relationship between Na and SPAD values has led to the adaptation of the SPAD meter to assess crop N status and to determine the plants need for additional N fertilizer (Peng et al 1995, 1996b; Balasubramanian et al 1999). SPAD readings indicate that plant N status and the amount of N to be applied are determined by the physiological N requirement of crops at different growth stages. Suggested N rates for different growth stages are provided in Table 1. Measuring SPAD values in the field SPAD readings are taken at 7- to 10-d intervals, starting from 14 d after transplanting (DAT) for transplanted rice (TPR) and 21 d after seeding (DAS) for wet direct-seeded rice (DSR). Periodic readings continue up to the first (10%) flowering. The youngest fully expanded leaf of a plant is used for SPAD measurement. Readings are taken on one side of the midrib of the leaf blade, midway between the leaf base and tip. In early growth stages, when leaves are too narrow to allow SPAD measurements on one side of the midrib, the leaf tip can be used for measuring SPAD values. SPAD readings are more stable under the shade between 1000 and 1600 h of the day. Thus, it is recommended that SPAD readings be taken under the shade and at the same time of day, if possible. A mean of 10-15 readings per field or plot is taken as the measured SPAD value. Whenever SPAD values fall below the set critical values, N fertilizer should be applied immediately to avoid yield losses from N deficiency.Table 1. Amount of N (kg ha-1) to be applied when measured SPAD values fall below established critical values. Crop duration Growth phase Short Medium Long (100-115 d) (125-135 d) (145-165 d) N (kg ha-1) Dry season Wet season

SPAD threshold or critical value The SPAD threshold or critical value indicates the leaf area-based critical N concentration (Na) in rice leaves. Whenever SPAD readings fall below the critical value, the crop suffers from N deficiency, and yields will decline if N fertilizer is not applied immediately. For example, a SPAD threshold value of 35 is equal to 1.41.5 g N m-2 of leaf area in semidwarf indica varieties (Peng et al 1996b). The SPAD threshold is not affected by luxury consumption because a plant will produce only as much chlorophyll as it needs, regardless of how much N is in the plant (Peterson et al 1993). Different SPAD threshold values are needed to optimize rice yields under different conditions (see discussion below). Factors affecting SPAD values Several factors affect SPAD values: radiation differences between seasons, plant density, varietal groups, nutrient status other than N in soil and plant, and biotic and abiotic stresses that induce leaf discoloration (Peterson et al 1993, Turner and Jund 1994). Users should be aware of these interfering factors and should take adequate precautions against them while using the chlorophyll meter. Effect of radiation (season). Seasonal differences in radiation affect the SPAD critical value. For example, in the Philippines, a SPAD threshold value of 35 works well for semidwarf indica varieties in transplanted rice systems during the dry season (DS). This critical value has to be reduced to 32 for TPR during the wet season (WS) when radiation is low due to continuous, heavy cloud cover for most of the growing season (WS rice yields are less than 60% of the DS yields) (Balasubramanian et al 1999). In India, however, the critical SPAD value for TPR is 37 for the wet (kharif) season and 3537 for the dry and winter (rabi) season to obtain high yields (IRRI-CREMNET 1998). This could be due to higher radiation in both seasons in India. Effect of plant or tiller density. Plant density as determined by the method of crop establishment influences SPAD readings. In the Philippines, a SPAD critical value of 35 optimizes grain yields for TPR with productive tillers of 450500 m-2 in the DS. When the same threshold was used for wet direct-seeded rice (W-DSR), N rates were high and grain yields were low (Balasubramanian et al 1999). Janaki and Thiyagarajan (p 24, in this issue) showed that, when the same SPAD threshold was used for various plant densities (33100 m-2) in TPR, more N was needed to produce similar grain yields in Coimbatore, India. Under Philippine conditions, a SPAD threshold of 30 is optimum for broadcast W-DSR with around 800 productive tillers m-2 (grain yield = 6,848 kg ha-1 in 1997 DS) and 32 for row W-DSR with 650 productive tillers m-2 (grain yield = 6,830 kg ha-1 in 1997 DS) for both WS and DS (Balasubramanian et al 1998). It was observed earlier that foliar N concentration in broadcast-seeded rice was less than that of TPR at all growth stages, irrespective of amount of N applied (Peng et al 1996a). This could be due to excessive vegetative growth resulting in dilution of plant N (N5

Transplanted rice: DATa Early 14-28 Rapid 29-48 Late 49-flowering Direct-seeded rice: DASc Early 21-35 Rapid 36-56 Late 57-floweringa

14-42 14-63 43-70 64-85 71-flowering 86-flowering 21-56 21-70 57-84 71-90 85-flowering 91-flowering

30 45b 30 30 45b 30

20 30b 20 20 30b 20

DAT = d after transplanting.bApply the large dose of 30 kg N ha-1 in the monsoon season or 45 kg N ha-1 in the dry season only once or twice maximum during the rapid growth stage. cDAS = d after seeding.

IRRN 25.1

deficient canopy) when semidwarf rice varieties developed for TPR systems are planted by broadcasting (Dingkuhn et al 1991). Thus, the critical SPAD value is inversely related to plant or tiller density. We expect that the critical SPAD values will be 3032 for high-density (650800 productive tillers m-2) and 3335 for medium-density (400500 productive tillers m-2) DSR. Further research is needed to validate the suggested critical SPAD values for direct-sown rice at different densities. Critical SPAD values for rice varietal groups. Different threshold values may have to be used for different varietal groups (Table 2). We suggest SPAD thresholds of 3032 for traditional or improved local and aromatic rice varieties and 3537 for semidwarf indica varieties in the transplanted system. Tropical rice hybrids generally have thinner leaves and a slightly lower leaf N concentration than inbreds. Thus, the SPAD threshold for tropical hybrids will be equal to or slightly less than that of inbred cultivars (S. Peng, IRRI, 1999, pers. commun.). Suggested SPAD thresholds for traditional, aromatic, and hybrid rice varieties have to be confirmed by further research. Even varieties with different grain types (coarse, medium, and fine) were shown to require different rates and patterns of N application to optimize grain yields when a single SPAD threshold value was used for all three varieties. The finer the grain type, the larger the amount of N required and the higher the number of split applications, especially after panicle initiation (Thiyagarajan and Aruna Geetha p 23, in this issue). Further research is needed to confirm whether rice varieties with different grain types require different SPAD critical values to optimize N use efficiency. Effect of soil type and nutrient status. Phosphorus (P)-deficient rice plants produce dark green leaves that could show high SPAD values (e.g., 39, vs 35 for normal plants). Peng et al (1999) observed that SPAD values were 1-2 units higher for zero-P (P-deficient) rice plants than for P-fertilized plants at a given leaf N concentration during the vegetative phase (mid-tillering) but not at the panicle initiation stage. Thus, if the SPAD meter is used to accurately determine leaf N concentration, a different regression equation between SPAD values and leaf N concentration should be used for P-deficient and P-sufficient rice plants during the vegetative phase. Zinc and boron deficiency appears to have a minimal effect on SPAD values. SPAD readings are generally lower in peat (organic) and acid sulfate soils. Sulfur deficiency produces chlorotic leaves showing low SPAD values, and using the SPAD method for N fertilization of rice in S-deficient soils may be misleading (as we observed in Myanmar). If the SPAD method is properly adapted to different varietal groups and crop-growing conditions and if appropriate critical SPAD values are established, this method will be highly useful for fine-tuning N fertilization of rice crops. Suggested critical values are summarized in Table 2. These values can be refined by one to two seasons of testing for locally important rice varieties and crop (environmental, nutritional, cultural) conditions.

Table 2. Suggested critical SPAD values for different seasons, cropping conditions, and rice varieties. Crop establishment Transplanted rice Varietal group Traditional, improved local, aromatic rice Semidwarf indica varieties Hybrid rice Panicle density (m-2) 300-400 400-500 400-500 SPAD value Wet season 30a-32 32a-35 32a-35 29-30b 32a 32b 32-35 Dry season 32 35b-37 35-37 30b 35 32b 32-35

Wet directseeded rice Broadcast sown All varieties Row seeded (drum seeded) All varieties

High: ~ 800 Medium: ~ 400-500 High: ~ 600-650 Medium: ~ 400-500

a Under Philippine conditions where radiation is low in the WS due to continuous cloud cover for most of the growing season (mean WS yield is less than 60% of mean DS yield). b Validated in the Philippines.

Cost and utility of chlorophyll meter Because the chlorophyll meter is too expensive (US$1,400 per unit) for farmers in developing countries, we developed a simple and inexpensive leaf color chart that can be used as an alternative decision-making tool to determine the need for N application in rice. Under practical on-farm situations, the color chart has proven to be as good as the chlorophyll meter for high grain yield and improved N use efficiency (IRRI-CREMNET 1998). The SPAD meter, however, is highly useful as a research and training tool for researchers, extension specialists, and crop consultants. In all N-related experiments, the SPAD meter can be used to determine the N status of test crops at different growth stages for a better understanding of N dynamics in soil-plantfloodwater systems. With the chlorophyll meter, agronomists can study the N requirement of new rice varieties and develop precise N recommendations for well-defined domains. It is a quick and accurate method for breeders to evaluate segregating lines for N use efficiency, and for biotechnologists to choose N-efficient lines for identifying genes responsible for high N use efficiency. Extension specialists can verify the validity of existing N recommendations by monitoring crop N status for one to two seasons and refine them, if necessary. Extension agents and crop consultants can precisely advise clients/farmers on need-based N fertilization of rice crops after testing the N status of plants in the field. This practice will enhance the quality of the relationship and the level of confidence between the advisors and their clients. Comparative efficiency of chlorophyll meter technique for grain yield and N use The technical efficiency of applied N is expressed in two forms: (1) agronomic efficiency of applied N (AEN), calculated as the

6

April 2000

additional grain yield per kilogram of N applied over the control, and (2) partial factor productivity of applied N (PFP-N), calculated as the grain yield divided by the amount of N applied. The SPAD technique is useful in measuring the current fertilizer use efficiency of farmers in different areas. Here are two examples: An increase in grain yield but with a higher N fertilizer use: The efficiency values are similar for the farmers practice and the SPAD method, indicating the efficient fertilizer use by farmers as in the case of the Philippines (Table 3). A savings in N fertilizer use without reducing grain yield: Here grain yields are similar for both the farmers and SPAD methods, but the amount of N used is much lower in SPAD plots compared with the farmers practice. Therefore, efficiency values are higher for the SPAD method than for the farmers practice or local recommendation as observed in India and Vietnam (Table 3). The farmers N fertilization practice has to be improved. On-farm trials have demonstrated the advantage of using the SPAD technique on rice. The increase in N use efficiency values (AEN and PFP-N) was due to higher grain yield with lesser N application in the SPAD-N plots; average savings in N fertilizerTable 3. Comparison of chlorophyll meter (SPAD) method with farmers practice or local recommendation for N management in rice at selected sites in various countries.a Treatment N used (kg ha-1) Grain yield (t ha-1) AEN PFP-N 48.0 44.7 53.9 b 52.2 b 83.2 a 58.1 117.2 86.5 51.6 b 118.4 a 35.4 45.4 45.7 33.0 57.5

ranged from 32 to 65 kg N ha-1 for various locations in India and Vietnam (Table 3). An inexpensive alternative to chlorophyll meter One alternative to using the expensive chlorophyll meter is for local researchers and extension agents to use data obtained from these trials to modify local fertilizer recommendations in amounts per application and timing. A much better option is to calibrate the inexpensive leaf color chart (US$1 per unit) with the chlorophyll meter and train farmers in its use to promote needbased N application in rice. Research needs on chlorophyll meter method Further research is needed to determine specific SPAD threshold values for fine-grain type, aromatic, and hybrid rice varieties. The effect of SPAD-guided N management on head rice recovery and grain quality is yet to be established. Preliminary results of ongoing research indicate that differential rates of N application can be worked out based on observed SPAD values at critical stages of growth (early tillering, active tillering, panicle initiation, and first [10%] flowering). If these observations are confirmed, the number of SPAD measurements and split N applications will be reduced. Suggested graded levels of N application based on an observed range of SPAD values at critical crop growth stages are given in Table 4 for validation. Researchers speculate that rice plants exposed to SPADregulated N supply will be healthier and less susceptible to lodging and diseases such as blast and bacterial leaf blight. We need further research to clarify the effect of need-based, SPAD-regulated N supply on plant health and plant resistance to lodging and diseases. Similarly, the effect of SPAD-guided N management on weed pressure and rice-weed competition is not understood; we require well-planned studies to assess the effect of the SPAD method of N management on the weed ecology on rice farms. We do not use basal N application with the SPAD method. This may create problems in soils with very low soil organic matter and N contents. Removal of basal N application in such soils may reduce seedling vigor and tillering in the early growth stages. We have to develop well-defined soil criteria or indicators to distinguish soil types where basal N application will be essential in addition to SPAD-based N topdressing. Finally, we also need to study the long-term effects of needbased N application on soil quality and soil nutrient-supplying capacity. ReferencesBalasubramanian V, Morales AC, Cruz RT. 1998. Chlorophyll meter threshold values for N management in direct wet-seeded, irrigated rice. Paper presented at the National CREMNET Workshop-cum-Group Meeting, Directorate of Rice Research (DRR), 7-9 Jan 1998, Hyderabad, India.

Philippines: Nueva Ecija, 1996 DS, 12 farms Control 0 3.7 c Farmers practice 126 6.0 b 18.2 SPAD-35 150 6.7 a 19.7 Philippines: Nueva Ecija, 1997 DS, 12 farms Control 0 5.0 b Farmers practice 139 7.5 a 17.7 b SPAD-35 138 7.2 a 15.7 b UT/DP 87 7.2 a 25.3 a India: Old Cauvery Delta, Padugai soil series, mean of 1997 & 1998 DS Control 0 4.9 b Local recommendation 125 7.3 a 18.6 SPAD-35 65 7.6 a 41.2 Basal N + SPAD-35 85 7.4 a 28.4 India: New Cauvery Delta, 1996 DS, 4 farms Control 0 5.3 b Local recommendation 125 6.4 a 8.8 b SPAD-35 60 7.1 a 51.0 a India: New Cauvery Delta, 1998 DS, 20 farms Control 0 3.6 b STCR recommendation 142 5.0 a 10.3 SPAD-35 110 5.0 a 12.9 LCC-4 108 4.9 a 12.6 Vietnam: Cai Lay District, 1996 WS, 6 replications Control 0 2.8 b Local recommendation 120 4.0 a 9.8 SPAD-32 70 4.0 a 17.8a

AEN (agronomic efficiency of applied N) = kg additional grain over control per kg N applied, PFP-N (partial factor productivity for applied N) = grain yield divided by applied N, DS = dry season,WS = wet season. Values followed by the same letter in each column are not significantly different at the 5% level by DMRT.

IRRN 25.1

7

Table 4. Suggested graded levels of N application based on observed ranges of SPAD values at critical growth stages of semidwarf indica varieties (100-115 d) in transplanted (TPR) and direct-seeded rice (DSR) systems.a TPR Growth phase DAT Preplant/basal Early tillering 0 14-18 SPAD value/ control yield Yield > 3 t ha-1 Yield < 3 t ha-1 SPAD > 37 SPAD 35-37 SPAD < 35 SPAD > 37 SPAD 35-37 SPAD 32-34 SPAD < 32 SPAD > 37 SPAD 35-37 SPAD 32-34 SPAD < 32 SPAD > 37 SPAD 35-37 SPAD < 35 Apply N (kg ha-1) Nil 20 Nil 20 30 Nil 30 40 50 Nil 30 40 50 Nil 20 30 DAS 0 21-25 DSR SPAD value/ control yield Yield > 3 t ha-1 Yield < 3 t ha-1 SPAD > 35 SPAD 32-35 SPAD < 32 SPAD > 35 SPAD 32-35 SPAD 30-31 SPAD < 30 SPAD > 35 SPAD 32-35 SPAD 30-31 SPAD < 30 SPAD > 35 SPAD 32-35 SPAD < 32 Apply N (kg ha-1) Nil 20 Nil 20 30 Nil 20 30 40 Nil 20 30 40 Nil 20 30

Active tillering

28-32

35-40

Panicle initiation

42-46

50-54

First (10%) flowering

56-60

64-68

a Values shown are based on research conducted at different sites in Asia covered by the Reversing Trends in Declining Productivity project and the Crop and Resource Management Network. Further validation is ongoing.

Balasubramanian V, Morales AC, Cruz RT, Abdulrachman S. 1999. On-farm adaptation of knowledge-intensive nitrogen management technologies for rice systems. Nutr. Cycl. Agroecosyst. 53:93-101. Dingkuhn M, Schnier HF, De Datta SK, Dorffing K, Javellana C. 1991. Relationships between ripening-phase productivity and crop duration, canopy photosynthesis, and senescence in transplanted and directseeded lowland rice. Field Crops Res. 26:327-345. Dobermann A, White PF. 1999. Strategies for nutrient management in irrigated and rainfed lowland rice systems. Nutr. Cycl. Agroecosyst. 53:1-18. Inada K. 1963. Studies on a method for determining deepness of green color and chlorophyll content of intact crop leaves and its practical applications. 1. Principle for estimating the deepness of green color and chlorophyll content of whole leaves. Proc. Crop Sci. Soc. Jpn. 32:157-162. Inada K. 1985. Spectral ratio of reflectance for estimating chlorophyll content of leaf. Jpn. J. Crop Sci. 54:261-265. IRRI-CREMNET (International Rice Research Institute Crop and Resource Management Network). 1998. Progress report for 1997. Manila (Philippines): IRRI. Kariya K, Matsuzaki A, Machida H. 1982. Distribution of chlorophyll content in leaf blade of rice plant. Jpn. J. Crop Sci. 51:134-135. Olk DC, Cassman KG, Simbahan G, Sta. Cruz PC, Abdulrachman S, Nagarajan R, Tan PS, Satawathananont S. 1999. Interpreting fertilizer use efficiency in relation to soil nutrient-supplying capacity, factor productivity, and agronomic efficiency. Nutr. Cycl. Agroecosyst. 53:35-41.

Peng S, Garcia FC, Laza RC, Cassman KG. 1993. Adjustment for specific leaf weight improves chlorophyll meters estimation of rice leaf nitrogen concentration. Agron. J. 85:987-990. Peng S, Laza RC, Garcia FC, Cassman KG. 1995. Chlorophyll meter estimates leaf area-based N concentration of rice. Commun. Soil Sci. Plant Anal. 26:927-935. Peng S, Garcia FV, Gines HC, Laza RC, Samson MI, Sanico AL, Visperas RM, Cassman KG. 1996a. Nitrogen use efficiency of irrigated tropical rice established by broadcast wet seeding and transplanting. Fert. Res. 45:123-134. Peng S, Garcia FV, Laza RC, Sanico AL, Visperas RM, Cassman KG. 1996b. Increased N-use efficiency using a chlorophyll meter on high-yielding irrigated rice. Field Crops Res. 47:243-252. Peng S, Sanico AL, Garcia FV, Laza RC, Visperas RM, Descalsota JP, Cassman KG. 1999. Effect of leaf phosphorus and potassium concentration on chlorophyll meter reading in rice plants. J. Plant Prod. Sci. 2(4):227-231. Peterson TA, Blackmer TM, Francis DD, Scheppers JS. 1993. Using a chlorophyll meter to improve N management. A Webguide in Soil Resource Management: D-13, Fertility. Cooperative Extension, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, Nebraska USA. Takebe M, Yoneyama T. 1989. Measurement of leaf color scores and its implication to nitrogen nutrition of rice plants. Jpn. Agric. Res. Q. 23:8693. Turner FT, Jund MF. 1994. Assessing the nitrogen requirements of rice crops with a chlorophyll meter method. Aust. J. Exp. Agric. 34:1001-1005.

8

April 2000

Plant breeding

Evaluation of anther culture-derived lines under upland conditions for the North Eastern Hill of IndiaA. Pattanayak and H.S. Gupta, Division of Plant Breeding, ICAR Research Complex for North Eastern Hill Region, Umiam 793103, Meghalaya, India E-mail: rcnehr@x400.nicgw.nic.in

The low productivity of upland rice in the North Eastern Hill of India makes it an unprofitable crop; yet, it occupies about 2025% of the cultivated rice area. Most local upland cultivars are long-duration, low-yielding, tall types that lodge at maturity. They are mostly susceptible to diseases such as blast and leaf scald. Because blast is a serious disease, a breeding program was started to develop blast-resistant upland rice lines with a yield potential of 44.5 t ha-1 and that mature in 120130 d. The higher production potential is expected to increase productivity, whereas the shorter duration will help increase cropping intensity. Anther culture shortens the breeding cycle because of rapid attainment of homozygosity, thereby shortening the period for developing new varieties. We report here the production and evaluation of doubled-haploid (DH) lines that outyielded all checks under rainfed upland conditions. Nine DH lines were produced by anther culture of F2 plants of a hybrid between PSN and 6131, following the

method of Gupta and Borthakur (1987). These lines were evaluated in replicated yield trials for 3 yr (1996-98) under the dryseeded upland conditions of Barapani (950 m asl) in Meghalaya, India. All DH lines, improved checks, and the local check were sown in terraces in randomized complete blocks with five replications in 5.6-m2 plots. Row-to-row and plant-to-plant distances were 20 cm and 10 cm, respectively. Data on various agronomic characters were recorded from five randomly selected plants from each replication. Unmilled rice yield, however, was calculated from the yield of 5.6-m2 plots in each replication. Days to flowering were recorded when

more than 50% of the plants in a plot flowered. Data on disease reaction were recorded following the IRRI standard evaluation system for rice. The average yield of RCPL 1-29 for 3 yr was the highest (4.4 t ha-1), followed by RCPL 1-27 (4.2 t ha-1) and RCPL 1-24 (4.0 t ha-1). The highest yielding improved check (IET13459) yielded 3.1 t ha-1 and the local check (Bali) yielded 2.6 t ha-1 (Table 1). All three DH lines had a compact and erect habit and intermediate maturity (123127 d), and were semidwarf (109.9111.8 cm) with high spikelet fertility (79.683.8%) (Table 2). They exhibited significantly higher yield per plant (7.99.2 g).

Table 1. Grain yielda (t ha-1) of doubled-haploid (DH) lines, improved checks, and local check, Barapani, Meghalaya, India, 1996-98. DH lines Year RCPL 1-29 1996 1997 1998 Ava

Improved checks RCPL 1-24 2.9 c 3.3 c 5.8 a 4.0 ab IET13459 2.2 d 3.2 d 3.8 d 3.1 cd IET13783 1.7 e 2.3 f 4.1 c 2.7 cd

Local check Bali 1.4 f 2.9 e 3.4 d 2.6 d

RCPL 1-27 3.6 b 3.3 b 5.8 a 4.2 ab

4.3 a 3.5 a 4.9 b 4.4 a

Values in a row followed by the same letter are not significantly different at the 5% level by DMRT.

Table 2. Comparison of some agronomic charactersa of doubled-haploid (DH) lines and checks evaluated at Barapani, Meghalaya, India, 199698. 1,000grain Yield plant-1 weight (g) (g) Head rice Milling (%) recovery (%) Blast reaction (under field conditions)b HR (0) HR (0) HR (0) S (7) HR (0) S (8)

Variety/ line

Days to maturity

Plant height (cm)

Fertile tillers (no.)

Panicle length (cm)

Spikelets panicle-1 (no.)

Spikelet fertility (%)

Hulling (%)

DH lines RCPL 1-29 RCPL 1-27 RCPL 1-24 Improved checks IET13459 IET13783 Local check Balia

126 123 127 116 129 129

111.8 111.5 109.9 118.3 131.2 131.2

4.3 4.0 3.9 3.2 2.5 2.5

23.7 22.8 23.5 20.6 20.6 20.6

133.7 129.7 124.4 124.8 145.3 145.3

82 80 84 78 85 85

7.9 9.2 8.7 4.7 4.0 4.0

29.5 40.4 28.7 29.4 26.3 26.3

80 83 79 71 80 82

73 76 65 58 67 67

67 69 58 35 53 59

Av of 3 yr. bBased on a 0 (HR) to 9 (HS) scale; HR = highly resistant, HS = highly susceptible, S = susceptible.

IRRN 25.1

9

Petei and Mocoi: two rice cultivars developed through anther culture in ArgentinaM.A. Marassi, IBONE, Facultad de Ciencias Agrarias (FCA), Universidad Nacional del Nordeste (UNNE), C.C. 209, 3400Corrientes; J.J. Marassi, J.E. Marassi, Facultad de Ciencias Agrarias y Forestales (FCAF), Universidad Nacional de La Plata, C.C. 31 (1900) La Plata, Buenos Aires; and L.A. Mroginski, IBONE, FCA, UNNE, Argentina E-mail:marassi@agr.unne.edu.ar

We developed two rice varieties, Petei and Mocoi, through anther culture. These varieties were released in 1997 for commercial cultivation in Argentina. Petei was developed from a cross involving cultivars Quella and Guayquiraro, which were made available to the rice program at the Julio Hirschhorm Experimental Station, FCAF. Selected plants from the F2 population of this cross were used for anther culture at the biotechnology laboratory, FCA, UNNE. Mocoi was developed from crossing two F1s (H342 and H161-28-2-2-1). H342s parents were Guayquiraro and Nucleoryza, whereas H161-28-2-2-1 had Calady 40 and IR110315-10 as parents. Anther culture was performed on the F1s and progenies were multiplied for further evaluation. Anther culture was used following the protocol given by Marassi et al (1993). Panicles from F1 H353 and F2 H319 at the booting stage containing pollen at the miduninucleate stage were pretreated (8 C for 8 d). Anthers were plated on N6, a callus induction medium (Chu et al 1975) supplemented with 2 mg naphthalene acetic acid L-1 and 0.5 mg kinetin L-1, and10

incubated in the dark at 27 2 C. Shoots were obtained on the regeneration medium. Flasks were transferred under light at 27 2 C. Plantlets were transferred to a rooting medium composed of MS (Murashige and Skoog 1962) culture solution that was free of hormones and supplemented with 8% sucrose. Plants were then transferred to the soil in the greenhouse until maturity, and the progeny was multiplied by the pedigree method. Data on callus formation and plant regeneration from anther culture of the two crosses are given in the table. The efficiency of anther culture (proportion of plants transferred to the soil

to total number of anthers cultured from the two crosses) was 8.4% for H319 and 5.4% for H353. Petei is 90 cm tall, resists lodging, and has intermediate threshability. It matures in 115 d and its yield potential is 8.5 t ha-1. Its grain is 5.9 mm long and 2.7 mm wide (short grain and special commercial type). The variety has 24.9% amylose, intermediate gelatinization temperature, 9.4% protein, and moderate resistance to blast. Because of its short growth duration, tolerance for low temperature, and good performance on saline soils, Petei is suited for growing in temperate climate under saline soil

Callus formation and plant regeneration from anther culture of rice. Calli with shoots (%) 75 70 Green shoots (%) 85 80 100. Number of cultured anthers

Progeny

Anthers (no.) 8,900 8,100

Calli (%) 14.6 11.0

Plantlets transferred to soil (%) 90 87

Anther culture efficiencya (%) 8.4 5.4

H319 (F2) H353 (F1)a

Number of plantlets transferred to soil Anther culture efficiency =

April 2000

Senescence of leaves, especially that of the flag leaf, was slower in the DH lines than in the checks. These lines had long bold grains with white kernel. RCPL 1-29, RCPL 1-27, and RCPL 1-24 were resistant to leaf blast under field conditions, whereas improved check IET13459 and Bali were both susceptible to blast (Table 2). In addition, Bali lodged at maturity, whereas IET13459 and IET13783 lodged only under high-fertility conditions. In contrast, the DH lines did not lodge even under highfertility conditions. Hulling percentages of the DH lines were 83% in RCPL 1-27,

80% in RCPL 1-29, and 79% in RCPL 1-24 (Table 2). Milling percentages were 76% in RCPL 1-27, 73% in RCPL 1-29, and 65% in RCPL 1-24 (Table 2). A multilocation trial was conducted on regional research farms during the 1998 wet season in five states (Arunachal Pradesh, Manipur, Meghalaya, Mizoram, and Nagaland) of the North Eastern Hill. The average unmilled yields of RCPL 1-29, RCPL 127, and RCPL 124 were 3.3, 2.5, and 3.1 t ha -1, respectively. The yield performance of RCPL 1-29 in Manipur and Meghalaya did not show a significant

difference (4.7 t ha-1 in Manipur and 4.9 t ha-1 in Meghalaya). No blast incidence was recorded in the DH lines in any of the five states. Average yield improvement over local checks was 46% in Mizoram, 36% in Meghalaya, 28% in Arunachal Pradesh, 19% in Manipur, and 17% in Nagaland. ReferenceGupta HS, Borthakur DN. 1987. Improved rate of callus induction from rice anther culture following microscopic staging of microspores in iron alum-haematoxylin. Theor. Appl. Genet. 74:95-99.

conditions. Petei was released for cultivation in areas near 36 S in Buenos Aires Province. Mocoi has a height of 75 cm, resists lodging, and has intermediate threshability. It matures in 120 d and its yield potential is 10 t ha-1. Its golden grain is 7.3 mm long and 2.3 mm wide (fine long commercial type). The endosperm has a high amylose content (26.6%) and the

protein content is 8.4%. It is moderately resistant to blast. Mocoi is suited for cultivation at 32 S near Villageny City ` (central region of Entre Rios Province) and in Buenos Aires Province. Both Petei and Mocoi are adapted to the new rice area (temperate with some saline areas) in Buenos Aires Province (3436 S) where traditional varieties are not well adapted.

ReferencesChu CC, Wang CC, Sun CS, Chen H, Yin KL, Chu CY, Bi FY. 1975. Establishment of an efficient medium for anther culture of rice through comparative experiments on the nitrogen sources. Sci. Sin. 18:659-668. Marassi MA, Bovo OA, Lavia GL, Mroginski LA. 1993. Regeneration of rice doubled haploids using a one-step culture procedure. J. Plant Physiol. 141:610-614. Murashige T, Skoog F. 1962. A revised medium for rapid growth and bioassay with tobacco tissue culture. Physiol. Plant. 15:473-479.

Performance of cold-tolerant rice lines developed through anther culture for mid-altitude areas of Meghalaya, IndiaA. Pattanayak, R.N. Bhuyan, H.S. Gupta, Division of Plant Breeding; M. Sreedhar and M.S. Prasad, Division of Plant Pathology, ICAR Research Complex for North Eastern Hill Region, Umiam 793103, Meghalaya, India E-mail: rcnehr@x400.nicgw.nic.in

Rice grown in mid-altitude areas (800 1,300 m asl) of the North Eastern Hill of India is exposed to suboptimum temperature during its life cycle, causing incomplete panicle exsertion, asynchronous flowering, and spikelet sterility. These factors reduce yield from 20% to 35%. Therefore, high-yielding indica cultivars do not have a significant impact in these areas because of thermosensitivity. Direct introduction of cold-tolerant japonica cultivars in these areas was not successful either. In addition, the long crop season does not allow more than one crop of rice per year; consequently, conventional breeding requires more time to develop new cultivars. Anther culture of F1s, on the other hand, helps speed up the breeding cycle by rapid fixation of homozygosity and simultaneous transfer of genes from one parent to the other. We report here the development of anther culture-derived doubled-haploid (DH) lines with cold tolerance at the reproductive phase. One of the linesDH7was the most promising and outyielded all checks in the mid-altitude areas. IR70 was crossed with a local cultivar, Khonorullo, which possesses cold tolerance at the reproductive phase and isIRRN 25.1

grown in high-altitude areas (more than 1,400 m asl). F1-derived anther culture produced 21 DH lines. These lines were evaluated in initial trials and, based on their performance, two lines, DH7 and DH21, were selected for a replicated yield trial. Both DH lines were evaluated along with high-yielding indica (IR70 and IR72) and improved cold-tolerant checks (RCPL 1-874 and RCPL 1-87-8) in replicated yield trials in three replications for 3 yr (1996-98) as transplanted rice in rainfed lowlands. The cold-tolerant parent was not included in the replicated trial because its yield was poor in the mid-altitude areas.

Data were recorded using the IRRI standard evaluation system for rice. Unmilled rice yield (t ha-1) was calculated from the yield of 5-m 2 plots in each replication. The average unmilled rice yield of DH7 (3.9 t ha-1) was significantly higher than that of the indica checks and coldtolerant check RCPL 1-87-8. In addition, DH7 and DH21 matured 11 and 21 d earlier than the improved cold-tolerant checks RCPL 1-87-4 and RCPL 1-87-8, respectively (Table 1). Panicle length and seed fertility of both DH lines were either better than or comparable with those of improved cold-tolerant checks (Table 1). DH7 also

Table 1. Comparison of agronomic charactersa of doubled-haploid (DH) lines, indica checks, and cold-tolerant checks, Meghalaya, India, 1996-98.b Variety Days to maturity Plant height (cm) 72.0 a 75.2 b 67.4 b 58.8 c 70.8 ab 71.0 ab Fertile tillers (no.) 7.4 a 7.1 a 6.5 a 7.6 a 7.6 a 7.0 a Panicle length (cm) 21.6 a 22.2 a 20.2 cd 19.4 d 20.6 bcd 20.7 bc Spikelets panicle-1 (no.) 96.8 a 109.0 a 82.2 b 82.4 b 88.2 b 76.6 a Spikelet fertility (%) 79 a 74 a 64 b 63 b 78 a 76 a Brown rice yield (t ha-1) 3.9 a 2.3 d 3.2 c 2.4 d 3.6 b 3.3 bc

DH lines DH7 151 c DH21 141 e Indica checks IR70 158 b IR72 148 d Improved cold-tolerant checks RCPL 1-87-4 162 a RCPL 1-87-8 162 aa

Values followed by a common letter are not significantly different at the 5% level by DMRT. bAv of 3 yr.

11

performed well under upland conditions. In the trials of the All-India Coordinated Rice Improvement Project in 1998, this line ranked third overall in the advanced varietal trial (upland) group with an average yield of 2.8 t ha-1, significantly superior to that of the improved check (2.3 t ha-1) and local check (2.2 t ha-1). DH7, DH21, and all the checks were moderately resistant to leaf blast under field conditions at Barapani (Table 2). Among parents, IR70 was moderately resistant, but Khonorullo was susceptible. DH7 and RCPL 1-87-4 were resistant to sheath blight under field conditions, whereas DH21, RCPL 1-87-8, and Khonorullo were moderately resistant. In contrast, IR70 and IR72 were moderately susceptible to sheath blight. DH7 was moderately susceptible to leaf scald in the field, whereas DH21, all checks, and IR70

Table 2. Reaction of doubled-haploid (DH) lines, parents, and checks to various diseases under field conditions at Barapani, India (950 m asl). Disease reactiona Variety Leaf blast Sheath blight Leaf scald Grain discoloration (scale 0-9) HR (0.5) HR (2.4) HR (0.6) HR (0.2) HR (2.0) HR (0.2) HR (0.1)

DH lines DH7 MR (2.8)b DH21 MR (2.6) Parents IR70 MR (2.4) Khonorullo S (6.0) Indica check IR72 MR (2.8) Improved cold-tolerant checks RCPL 1-87-4 MR (2.2) RCPL 1-87-8 MR (2.6)

R (1.0) MR (3.0) MS (5.0) MR (3.0) MS (5.0) R (1.0) MR (3.0)

MS (4.0) MR (3.3) R (1.7) S (6.0) R (2.2) HR (0.3) R (1.2)

a HR = highly resistant, R = resistant, MR = moderately resistant, MS = moderately susceptible, S = susceptible. bNumbers in parentheses are average disease scores over 3 yr on a scale of 0 (highly resistant) to 9 (highly susceptible).

were resistant to the disease. The coldtolerant parent Khonorullo, however, was susceptible to leaf scald. All lines were

highly resistant to grain discoloration although IR70 showed some grain discoloration in some replications (Table 2).

Reactions to an inferred resistance of Indian and Bangladesh rice varieties to bacterial blightK.S. Lee, E.R. Angeles, and G.S. Khush, Plant Breeding, Genetics, and Biochemistry Division, IRRI E-mail: k.s.lee@cgiar.org

Bacterial blight (BB) caused by (Xanthomonas oryzae pv. oryzae, Xoo) is one of the most important diseases of rice that cause substantial yield losses. Yield losses from this disease range from 10% to 30% under field conditions (Reyes et al 1983). In the absence of effective chemical control, cultivation of resistant varieties is the most practical, effective, and economical approach for managing this disease to keep losses below economic injury levels. Thus, incorporation of BB resistance has been a major component of most rice improvement programs in Asia (Khush et al 1989, Mew and Khush 1981). Ogawa et al (1991) classified BBresistant rice cultivars into eight groups based on their reaction patterns to four Philippine races of Xoo and the BB genes they possess. These groupings made it possible to determine gene(s) for12

resistance to Xoo in BB-resistant cultivars. We tested 170 cultivars from the International Rice Germplasm Center (IRGC) of IRRI for reactions to six Philippine races of Xoo to determine genes for resistance to BB. A set of near-isogenic lines (NIL) for genes with BB resistance, IRBB4 (Xa4), IRBB5 (xa5), IRBB13 (xa13), and IR24 (the susceptible check), to all races of Xoo was inoculated to confirm the six isolates of Xoo. Results showed that 39 (23%) of the cultivars were resistant to races 1, 2, 3, and 5; moderately susceptible to race 4; and susceptible to race 6. This reaction pattern is typical of varieties belonging to the DZ192 group (see table). Thus, these cultivars possibly carry xa5. All cultivars classified in this group originated from Bangladesh. The BJ1 group represents 62 (36%) cultivars and was resistant to all six races of Xoo (see table). These cultivars may carry

xa5 and xa13. Gene xa5 governs resistance to races 1, 2, 3, and 5, whereas xa13 conveys resistance to race 6. On the other hand, the high level of resistance to race 4 in these cultivars is due to the complementary action of the two genes. Cultivars assigned to this group come from India and Bangladesh. The remaining 69 cultivars (41%) showed resistance to races 1, 2, 3, 4, and 5 but are susceptible to race 6, suggesting that they may possess Xa4 and xa5 genes (Makhmal Mehi group). Cultivars classified under this group come from India and Bangladesh (see table). The classification of 170 cultivars into varietal groups based on reactions to BB pathotypes is useful in selecting for donor parents in resistance breeding programs. It is also a simple way to determine resistance genes in resistant cultivars.April 2000

ReferencesKhush GS, Mackill DJ, Sidhu GS. 1989. Bacterial blight of rice. In: Breeding rice for resistance to bacterial blight. Manila (Philippines): IRRI. p 207-217. Mew TW, Khush GS. 1981. Breeding for bacterial blight resistance in rice at IRRI. In: Proceedings of the Fifth International Conference on Plant Pathogenic Bacteria. Cali (Colombia): Centro Internacional de Agricultura Tropical (CIAT). p 504-510. Ogawa T, Busto GS, Tabien RE, Romero GO, Endo N, Khush GS. 1991. Grouping of rice cultivars based on reaction pattern to Philippine races of bacterial blight pathogens (Xanthomonas campestris pv. oryzae). Jpn. J. Breed. 41:109-119. Reyes RC, Vera-Cruz CM, Aballa TC, Baraoidan MR, Mew TW. 1983. Bacterial disease of rice. In: Rice production manual. Laguna (Philippines): UPLB College of Agriculture. p 341-352.

Grouping of cultivars based on reaction pattern to six Philippine races of Xoo. Group DZ192 Cultivars DF1, Mohishdo, Molla Diga, Chengri, Hanumanjata, Katakchikou, Pankhiraj, Bilat Kolom, Aus15, Aus18, Aus21, Aus22, Aus70, Aus 76, Aus114, Aus225, Aus268, Aus277, Aus320, Aus323, Aus330, Aus334, Aus367, Aus447, Aus450, Aus462, Aus143, Chungur Bali, Holai, Sultanjata, Bangal Bokri, Bolorum, Kachilon, Jholi Aus, Porangi, Sthania Shon, Surjamoni, Bazail 424, Maitura Bazail 407, ARC10025, Phcar Tien P65, Beri, Terabali, Kaika, Dudh Bhawalia, Hida, Dholi Boro, Boteswar, Hanpa, Loroi, Aus28, Aus128, Aus133, Aus154, Aus175, Aus176, Aus190, Aus207, Aus265, Aus267, Aus283, Aus287, Aus355, Aus364, Kali Atia, Korchamuri, Norai, Saita, Baila Borki, Kalonchi, Taothabi, Lal ahu, Rerm Bilash, ARC10376, Sabakari, Marich Ful, Begun Bahar, Inda, Kali Haitya, Laksmilota, Saita, Choudda Mugur, Dulpi, AC10-38, Bazail 197, Bazail 1187, Dharial, Baishbish, Chinsurah 2, Kalimekri 391, ARC6068, ARC7128, ARC10313, ARC10520, Bakoi, Jhur, India Dular, Laksmi Dia, Laksmijota, Aswina Laki 659, Lakhsmi Digha, Bhaturi, Pankiraj, Bolium, Baturi, Ngasein Kalagyi, DD96, ARC7098, ARC10372, ARC11332 Benamuri, Garia, Munshilhail, Tepi Boro, Bowalia 2, Goria, Lema, Aus19, Aus35, Aus46, Aus77, Aus98, Aus126, Aus142, Aus148, Aus151,Aus157, Aus159, Aus173, Aus218, Aus243, Aus259, Aus269, Aus301, Aus304, Aus350, Aus464,Aus270, Aus272, Aus273, Aus275, Aus282, Aus297, Aus306, Aus307, Aus310, Aus314, Aus333, Aus340, Aus341, Aus342, Aus349, Aus406, Aus455, Aus456, Jogli, Kalamanik, Banshi Kolom, Banshiraj, Bazail 924, Bazail 975, ARC6608, ARC7327, Latu, Manik-Mundu, Kamoni Sail, Dharial, Dular Origin Bangladesh

BJ1

Bangladesh and India

Makhmal Mehi

Bangladesh and India

Digital Literacy for Rice ScientistsTo help rice scientists take advantage of new information and communication technologies, the IRRI Training Center has developed the Digital Literacy Course for Rice Scientists. The course aims to provide scientists with information about what resources are available on the Internet and how they can go about accessing these resources. The course is unique in that, it focuses on the needs of rice scientists, it provides a forum for rice scientists to share their experiences and Internet resources with other rice scientists online, and it establishes a learner-centered knowledge network in the form of an online community centered on rice research. The topics covered by the course include What is the Internet What is the World Wide Web and what makes it work Key Internet terminology How to use the Internet for communication with other scientists How to use Web browsers How to search for information efficiently and effectively What are some of the good sources of information for rice scientists available on the Internet How to cite Internet documents What training opportunities are available online Connection to the Internet offers national scientists with a low-cost communication medium with other scientists linked to the Internet, gives them access to the ever-growing body of information available on and through interlinked computers throughout the world, and provides access to formal and informal training offered online from virtually anywhere. The course was developed by Robert T. Raab and Buenafe Abdon of the IRRI Training Center. Watch for more announcements in subsequent issues of IRRN.IRRN 25.1

13

Pest science and management

Effect of variety and sowing date on false smut incidence in upland rice in Edo State, NigeriaM.O. Ahonsi, A.A. Adeoti, I.D. Erinle, M.D. Alegbejo, Crop Protection Department, Institute for Agricultural Research, Samaru, PMB 1044; Ahmadu Bello University, Zaria; B.N. Singh, West Africa Rice Development Association (WARDA), c/o International Institute of Tropical Agriculture, Ibadan, Nigeria; and A.A. Sy, WARDA, Bouak, Cte dIvoire E-mail: m.ahonsi@cgiar.org

Table 2. Effect of sowing date on false smut incidence at two sites on the outskirts of OvbiowunEmai, Edo State, Nigeria. Sowing date 2-3 Apr 16-17 Apr 2-3 May 16-17 May 2-3 Jun 16-17 Jun LSD (0.05) CV (%) Sowing date Site Sowing date site Assessment date 30-31 Jul 13-14 Aug 29-30 Aug 14-15 Sep 29-30 Sep 13-14 Oct Mean disease incidence (%) 0.0 3.1 1.2 51.6 48.5 29.6 8.65 33.19 0.0001 0.7643 0.5262 Pr>F

About IRRIs Library and Documentation ServiceDid you know... ... that IRRI has the worlds biggest rice library? ... that it provides a free photocopy service1 to rice scientists everywhere? ... that its catalogue and rice bibliography are available on the World

14

False smut induced by Ustilaginoidea virens (Cke.) Tak. is a prevalent inflorescence disease of upland rice in Edo State, southern Nigeria. The incidence is high in areas 75150 km northeast of Benin City in Edo State. Widely grown varieties FARO 3 (Agbede) and FARO 46 (ITA150) are severely infected. The disease has been observed yearly since 1989. Two field experiments were conducted in farmers fields during the 1993 and 1994 wet seasons to evaluate the effect of plant variety and sowing date on false smut incidence. Each experiment was conducted at two sites approximately 20 km apart on the outskirts of OvbiowunEmai (longitude 67 E and latitude 67 N) and 90 km northeast of Benin City. The location is in a humid forest zone. Incidence was taken as percentage of hills infected in a quadrant of 4 m2 in each replicate. In the first experiment, seven upland rice varieties were planted on three different dates depending on maturity period to ensure flowering by late August. Varieties reacted differently to false smut infection (Table 1). Although false smut incidence was apparently higher at one of the sites, the reaction of varieties to the disease followed the same trend at both sites and the site variety interaction was not significant. Varieties ITA150, FARO 49 (ITA315), FARO 3 (Agbede), and ITA335 were the most susceptible to false smut. ITA316 and Ex-China showed some resistance, while FARO 41 (IRAT170) was completely free from infection. In the second experiment, Agbede was planted on six dates at 2-wk intervals. False smut incidence on this variety at both

sites on the respective planting dates was not significantly different. Rice sown with early rains, between 2 April and 3 May, was virtually free from the disease (Table 2). But rice sown between 16 May and 3 June was the most infected. It is evident that varietal differences occur in false smut infection and planting dates affect disease incidence. Planting resistant varieties such as IRAT170 and Ex-China and early planting (by April) reduce false smut damage.

Table 1. Incidence of false smut in seven upland rice varieties tested under field conditions at two sites on the outskirts of Ovbiowun-Emai, Edo State, Nigeria. Variety ITA315 ITA335 ITA316 ITA150 IRAT170 Ex-China Agbede (FARO 3) LSD (0.05) CV (%) Variety Site Variety site Mean disease incidence (%) 40.5 43.3 8.6 36.1 0.0 2.3 40.6 12.09 41.30 0.0001 0.0271 0.2744 Pr>F

Wide Web for searching, 24 hours a day2? ... that IRRI Library staff are waiting right now to receive your requests3? We hope to be of service to you soon!Maximum of 50 pages per request Web address: http://ricelib.irri.cgiar.org Write to Carmelita Austria at this address: Library and Documentation Service, International Rice Research Institute, MCPO Box 3127, Makati City 1271, Philippines E-mail address: c.austria@cgiar.org2 3 1

April 2000

Stem borer species composition in Tamil Nadu, IndiaJ.C. Ragini, D. Thangaraju, and P.M.M. David, Department of Agricultural Entomology, Agricultural College and Research Institute, Tamil Nadu Agricultural University, Killikulam, Vallanad 628252, India

Species composition (%) 90 80 70 60 50 40 30 20 10 0Tuticorin Kanyakumari Tirunelveli Madurai Tanjore Coimbatore Dharmapuri Vellore

YSB PSB DSB

Districts Fig. 1. Relative abundance of stem borer species in some districts of Tamil Nadu.Vertical lines indicate standard deviation.

Species composition (%) 100 YSB PSB DSB

80

60

40

20

ReferencesDutt N, Kundu DK. 1983. Stem borer complex of paddy in West Bengal. Indian J. Entomol. 45:229-236. Heinrichs EA. 1994. Insect pests of rice planttheir biology and ecology. In: Heinrichs EA, editor. Biology and management of rice insects. New Delhi: Wiley. p. 363-486. IRRN 25.10 25/SS 40/ET 50/AT 70/MT 80/FL 100/HD Crop age/stageFig. 2. Relative abundance of stem borer species in relation to crop growth stage. Vertical lines indicate standard deviation. SS = seedling stage, ET = early tillering, AT = active tillering, MT = maximum tillering, FL = flowering, HD = heading.

15

We conducted a district-level survey in 199798 cropping seasons in major rice-growing areas of Tamil Nadu to understand the pattern of stem borer species occurrence. In each of two or three rice fields in each district where rice is transplanted in irrigated lowlands, at least 50 infested tillers showing deadhearts or whiteheads were dissected at various growth stages to identify the species of larvae involved (Heinrichs 1994). Species composition was calculated by the formula (total larvae of particular species) / (total number of larvae collected) 100. The survey revealed that rice was damaged by three species of stem borers yellow stem borer (YSB) Scirpophaga incertulas (Walker), pink stem borer (PSB) Sesamia inferens (Walker), and dark-headed stem borer (DSB) Chilo polychrysus (Meyrick). YSB was collectively more numerous (63.9%) than PSB (22.8%) and DSB (13.3%) (Fig. 1). These species have been recorded earlier from different parts of India (Pathak 1968, Dutt and Kundu 1983, Kushwaka 1988, Upadhyay and Diwkar 1992). YSB occurred predominantly in all districts and its composition varied between 52.7% in Tirunelveli and 82.8% in Vellore. The occurrence of PSB and DSB varied among survey districts. Although PSB was more abundant than DSB in Tuticorin, Madurai, Tanjore, and Dharmapuri (23.6 39.2%), DSB was more common in Tirunelveli, Kanyakumari, and Vellore (17.2 39.7%). The damage at seedling stage was fully due to S. incertulas, but the infestation decreased slowly at later stages (Fig. 2). On the other hand, PSB infestation, which was low at the seedling stage, increased steadily through tillering stages with a decrease in the YSB population in most districts. PSB was more abundant than YSB at later stages. DSB was always less numerous in all districts.

Kushwaka KS. 1988. Insect pest complex of rice in Haryana. Bull. Entomol. 25:100-102. Pathak MD. 1968. Ecology of common insect pests of rice. Annu. Rev. Entomol. 13:257-294.

Upadhyay KR, Diwkar MC. 1992. Present status of rice insect pests in India. Plant Prot. Bull. 44:38-39.

An integrated approach to managing rice stem nematodesS. Chakraborti, Department of Agricultural Entomology, Bidhan Chandra Krishi Viswavidyalaya Mohanpur 741252, India

Ufra disease caused by Ditylenchus angustus (Butler) has become prominent because of its increasing rate of occurrence and infestation intensity, and expansion in newer areas. It was first reported in east Bengal (Bangladesh) (Butler 1913); it now occurs in Bangladesh, Myanmar, Egypt, India, Madagascar, Malaysia, Thailand, and Vietnam. Ufra is found mainly in deep water and usually spreads through floodwater (Miah 1984), but it can also cause serious damage in irrigated and rainfed lowland rice (Cuc and Kinh 1981). It had been reported to cause 50100% yield loss in Vietnam (Cuc and Kinh 1981) and 4080% yield loss in India (Chakraborti et al 1985). The Northern Old Alluvial Zone of West Bengal, which is part of the prime rice tract of India, is a floodprone area. Submergence (0.51 m) for long periods has contributed immensely to the entrenchment of the nematode. There is, however, a lack of scientific documentation on the control or management of ufra disease in this zone. This called for a study on the efficacy of an integrated approach to ufra management. Irrigated transplanted rice (IET4094) was raised following standard agronomic practices including fertilizer management. The experiment was set out in a randomized block design with three treatments and five replications per treatment. Each plot measured 3 2 m. Spraying was done with a 5-L-capacity brass sprayer (400 L ha-1). Granules were applied

manually. Ten randomly selected hills plot-1 were observed for nematode and sheath rot-infected tillers at 15-d intervals. An ufra disease rating was taken using Butler (1913): Ufra I: Thor or swollen ufra panicles did not emerge and were completely enclosed within the flag leaf sheath. Ufra II: Pucca or ripe ufrapanicles emerged partially and bore some unfilled grains. An elaborate pilot study was made to test the effectiveness of individual components separately against the nematode and the fungus. Some components were nematode-specific; some were fungus-specific. An integrated package was designed to provide simultaneous protection against both because ufra becomes serious in the presence of sheath rot fungus. Treatment 1: An integrated approach, comprising a seed treatment with ethyl mercuric chloride (EMC) at 3 g ai kg-1; seedbed treatment with NSKP at 10 g ai m -2 and carbofuran at 2 g ai m -2; seedling root dipping for 1 h in neem seed kernel extract (NSKE) at 10 mL ai L-1 followed by 8 h in carbofuran at 2.5 g ai L-1; 3-wk delay in sowing; burning of crop residues after sundrying in the field; deep plowing followed by soil solarization; crop rotation of jutemustardrice; use of trap crop Magursal, a local rice cultivar as seedbed trap crop; neem cake at 300 kg

ha-1 7 d before transplanting; carbofuran at 1 kg ai ha-1 just before transplanting; NSKE at 8 kg ai ha-1 10 d after transplanting (DAT); carbofuran at 1.5 kg ai ha-1 at 30 DAT; carbendazim at 3 g ai L-1 at 35 DAT; and NSKE at 15 mL ai L-1 at 50 DAT. Treatment 2: Chemical method with carbofuran at 2.5 g ai L-1 for seedling root dipping; carbofuran at 1.5 kg ai ha-1 just before transplanting; carbofuran at 1.5 kg ai ha -1 once every 30 DAT; and carbendazim at 3 g ai L-1 once every 35 DAT. Treatment 3: Controlonly water was sprayed. Results (Table 1) showed that treatment 1 (integrated approach) was very effective against the nematode. The population was maintained at a steady low level (4.5% and 3.8% ufra infection at 45 and 60 DAT, respectively). Fresh tillers greatly compensated for the infection loss. Results also showed that treatment 1 was very effective against sheath rot (Table 2) and thus prevented severe ufra infection due to a combination of sheath rot infection; it also had a good yield (3.4 t ha-1). Treatment 2 was effective but the yield loss was quite substantial because sheath rot infection made ufra infection more severe. The integrated treatment was generally superior to the chemical method. Seedbed treatment, seedling root dipping, delayed sowing, burning of crop residues, deep plowing and soil solarization, nonhost crop rotation, use of trap crop,

Table 1. Mean percentage of ufra-infected tillers 10 hills-1, proportion of ufra types in ufra infection, and nematode population in 250 g of soil. Treatmenta 30 DATb 1 2 3 12.6 (21) c 25.2 (30) 42.2 (40) C.D. at 5% 3.64a

% ufra-infected tillers 45 DAT 4.52 (12) 15.93 (24) 48.37 (44) 5.28 60 DAT 3.85 (11) 14.23 (22) 54.27 (47) 5.43

Proportion of ufra types (%) Ufra I 19.38 (26) 26.35 (31) 32.86 (35) 3.58 Ufra II 80.62 (64) 73.65 (59) 67.14 (55) 4.54

Mean nematode population in 250 g soil (0-20 cm) (no.) Initial 302.1 304.5 296.6 10.13 Final 10.2 62.5 494.4 8.18

1 = integrated method, 2 = chemical method, 3 = control. bDAT = days after transplanting. cNumbers in parentheses are arcsine VP transformations.

16

April 2000

Table 2. Mean percentage of sheath rot-infected tillers 10 hills-1 and yield. Treatmenta % rot-infected tillers 30 DAT b 1 2 3 5.2 (13.17) c 11.1 (19.47) 45 DAT 2.8 (9.55) 8.3 (6.74) 60 DAT 2.7 (9.44) 8.6 (17.06) 3.4 2.8 1.6 0.64b

ReferencesButler EJ. 1913. Disease of rice: an eelworm disease of rice. Agric. Res. Inst. Pusa Bull. 34B:1-27. Chakraborti HS, Nayak DK, Pal A. 1985. Ufra incidence in summer rice in West Bengal. Int. Rice Res. Newsl. 10(1):15-16. Cuc NTT, Kinh DN. 1981. Rice stem nematode disease in Vietnam. Int. Rice Res. Newsl. 6(6):14-15. Das P. 1996. An integrated approach for management of rice stem nematode Ditylenchus angustus in deep water in Assam. Indian J. Nematol. 26(2):222-225. Miah SA. 1984. Disease problems and progress of research on ufra disease of rice in Bangladesh. Int. Rice Com. Newsl. 33(2):3538.

Yield (t ha-1)

% infected panicles % nonfilled grains 10 hills-1 panicle-1

7.0 (14.17) 18.5 (25.46) 48.3 (44.01) 4.25c

16.8 (24.21) 25.2 (30.12) 49.2 (44.55) 6.17

20.2 (26.69) 27.4 (31.53) 38.3 (38.22) C.D. (5%) 2.84 3.15 5.34

1 = integrated method, 2 = chemical method, 3 = control. DAT = days after transplanting. Numbers in parentheses are arcsine VP transformations.

a

and applying neem cake and carbofuran just before transplanting and NSKE at 10 DAT can check the inflow of primary nematode inocula. Seed treatment, seedbed treatment with NSKP, burning of

crop residues, deep plowing and soil solarization, and neem application were prophylactic against the fungus. Results of this investigation generally agree with those of Das (1996).

Pathogenicity of cyst nematode, Heterodera sacchari, on rice in sand and clay soilD.L. Coyne, Natural Resources Institute, Chatham Maritime, Kent ME4 4TB, and R.A. Plowright, CABI Bioscience, Bakeham Lane, Egham, Surrey TW20 9TY, UK E-mail: dannycoyne@compuserve.com

The cyst nematode, Heterodera sacchari, occurs on rice throughout West Africa (Bridge et al 1990) but is also found outside Africa. Oryza sativa cultivars can be highly susceptible to H. sacchari (Plowright et al 1999). Production losses from H. sacchari infection on rice can be high under upland conditions, but are less severe under flooded conditions (Babatola 1983). This study assessed the pathogenicity of H. sacchari on improved O. sativa cv. IDSA6 on two different soil types under upland conditions: sand (9% clay, 15% silt, 75% sand) and clay loam (20% clay, 24% silt, 56% sand). Two seeds were sown in 8-L plastic pots filled with steam-sterilized soil, and seedlings thinned to one at emergence. Pots measuring 30 cm in diameter and 25 cm deep were perforated at the base and were watered daily from the base. They were arranged on benches in a randomized complete block design. Mature cysts of H. sacchari were mixed into the upper 5 L of the soilIRRN 25.1

by hand, prior to sowing, at seven densities (Pi): 0, 10, 20, 50, 100, 200, and 400 cysts pot-1, with 10 replications. Cysts were derived from mature IDSA6 plant roots following several generations in the pot in the screenhouse. The number of juveniles hatching into water from a subsample of cyst inoculum was assessed to estimate viable egg density. At 84 d after sowing (DAS), plant height was measured and relative leaf chlorophyll content recorded, using the Minolta SPAD-502 meter on the uppermost fully developed leaf. At harvest, leaf dry weight was recorded after oven drying, root fresh weight was recorded after rinsing each root system and dabbing dry, and grain weight was recorded. All data were analyzed using ANOVA. The relationship between initial nematode egg density (estimated from hatching assay) and relative yield (Y) (yield obtained with no H. sacchari stress) was established using Yercurve for DOS software, which

fitted the equation: Y = Ymin + (1Ymin)z(P-T) where z is a constant