Identification of waterlogging tolerant Brachiaria hybrids Joisse Rincón, John Miles and Idupulapati Rao

International Center for Tropical Agriculture (CIAT), A.A. 6713, Cali, Colombia (E-mail: j.rincon@cgiar.org)

Two trials were conducted outside in Forages patio area of CIAT Palmira during 2008 to determine differences in tolerance to waterlogging among 79 Brachiaria genotypes (5 hybrids of BR02NO series; 8 hybrids of BR04NO series; 20 hybrids of BR05NO series; 10 hybrids of MX02NO series; 28 hybrids of BR06NO ; 3 parents - CIAT 606; B. Ruz 44-02; CIAT 6294; and 5 checks - CIAT 679; CIAT 6133; CIAT 26110; CIAT 36061; CIAT 36087). Waterlogging treatment was imposed by applying excessive water to the pots (5 cm over soil surface) for 15 days. The two trials were planted as randomized complete block with seven replications. Each experimental unit consisted of one pot filled with 3.5 kg of fertilized top soil (0-20 cm) from Santander de Quilichao’s Oxisol and sown with two vegetative propagules (stem cuttings). An adequate amounts of fertilizer were supplied to the soil at the time of planting. Plants grew for 60 days under 100% field capacity of soil moisture. Leaf chlorophyll content (in SPAD units) and leaf photosynthetic efficiency (Fv/Fm) were measured at weekly intervals during the treatment. At the end of the 15 days of treatment, green leaf area (cm2 pot-1), green leaf biomass (g pot-1), dead leaf biomass (g pot-1) and stem biomass (g pot-1) were measured and green leaf biomass proportion to total shoot biomass was determined.

Total chlorophyll content (SPAD)

20 25 30 35 40 45 50

0

20

40

60

80

100CIAT 6133

CIAT 679

CIAT 26110

CIAT 606BR04 2069

BR06 0850BR05 01609

MX02 03641BR05 0334BR05 01469

CIAT 36087CIAT 36061

BR02 1794 BR06 1132BR04 3207

CIAT 6294

Gre

en le

af b

iom

ass

prop

ortio

n (%

)

Mean = 34.5LSD0.05 = 5.46

Bruz 4402

Mean = 20.61LSD0.05 = 13.78

Table 1. Correlation coefficients (r) between green leaf biomass proportion (%) and other shoot traits of 79 Brachiaria genotypes under waterlogging in an Oxisol from Santander de Quilichao.

Plant traits Waterlogging Green leaf biomass (g pot-1) 0.91***Total chlorophyll content (SPAD) 0.48***Green leaf area (cm2 pot-1) 0.81***Dead leaf biomass (g pot-1) -0.66***Stem biomass (g pot-1) 0.36***Leaf photosynthetic efficiency (Fv/Fm) 0.44***

*, **, *** Significant at the 0.05, 0.01 and 0.001 probability levels, respectively.

Results

HarvestPhenotypic differences

Waterlogging treatment

Physiological variablesa. Chlorophyll contentb. Photosynthetic efficiency

a. b. d.

c.

c. Stem, green leaf, dead leaf biomass.d. Leaf area.

Waterlogging for two weeks

Figure 3. Relationship between green leaf biomass proportion and the total chlorophyll content for 79 Brachiaria genotypes under waterlogging. Brachiaria genotypes that developed greater green leaf biomass proportion and total chlorophyll content were identified in the upper, right hand quadrant.

Figure 4. Relationship between green leaf biomass and dead leaf biomass for 79 Brachiaria genotypes under waterlogging treatment for 15 days. Brachiaria genotypes that developed greater green leaf biomass and lower dead leaf biomass were identified in the upper, left hand quadrant.

Figure 1. Methodology for screening Brachiariagenotypes under waterlogging conditions.

Baruch Z. 1994. Responses to drought and flooding in tropical forage grasses. Plant and Soil 164: 87-96.Días-Filho M. B. 2001. Tolerance to flooding in five Brachiaria brizantha accessions. Pesq. Agropec. Bras., Brasilia, 37: 439-447.J. Rincón, R. Garcia, J.W. Miles and I. M. Rao (CIAT). 2007. Genotypic variation in waterlogging tolerance of preselected sexual hybrids of Brachiaria. In: Tropical Grasses and Legumes: Optimizing genetic diversity for multipurpose use (Project IP5). Annual report 2007. CIAT. Cali, Colombia, pp 46-47. I. M. Rao, J. Rincón, R. Garcia, J. Ricaurte and J.W. Miles (CIAT). 2007. Screening for tolerance to waterlogging in Brachiaria hybrids. Poster paper presented at the international annual meeting. ASA-CSSA-SSSA. 2007.

This work is partially supported from the funds of Grupo Papalotla, Mexico.

BR05 1609

BR05 1469

CIAT 6133

Check cultivar Tolerant hybrid Sensitive hybrid

Figure 2 . Influence of waterlogging on shoot growth at harvest time (15 days of waterlogging treatment). One check cultivar, tolerant hybrid and sensitive hybrid.

At 7 days after of establishment of waterlogging stress, the majority of plants turned chlorotic. At 15 days after waterlogging treatment, several hybrids were dead. Two checks, B. humidicola CIAT 6133 and CIAT 679 were outstanding in total chlorophyll content, green leaf biomass proportion to total shoot biomass and had lower dead leaf biomass (Figures 3 and 4). Three hybrids BR04NO/2069, BR06NO/0850 and BR05NO/1609 were superior in their production of green leaf biomass (Figure 4). Two other hybrids BR04NO/3207 and BR06NO/1000 showed moderate level of tolerance to waterlogging based on green leaf biomass proportion to total shoot biomass (Figure 3). Among checks the hybrid cv. Mulato 2 (CIAT 36087) showed lower level of waterlogging tolerance.

Identified three hybrids (BR04NO/2069, BR06NO/0850 and BR05NO/1609) that were superior to the other hybrids in their tolerance to waterlogging.

This study clearly showed that there is marked genotypic variation in waterlogging tolerance in Brachiaria and we could quantify the differences in waterlogging tolerance based on four plant traits including green leaf biomass, green leaf area, leaf chlorophyll content, dead leaf biomass and green leaf biomass proportion to total shoot biomass.

Introduction

Material and Methods

References

Conclusions

Centro Internac ional de Agricultura TropicalInternational Center for Tropical Agriculture

Dead leaf biomass (g pot-1)

0 2 4 6 8 10 12 14

Gre

en le

af b

iom

ass

(g p

ot-1

)

0

2

4

6

8

10

CIAT 6133CIAT 679

CIAT 26110

CIAT 606

BR04 2069 BR06 0850

BR05 1609

CIAT 36087BR05 0334

CIAT 6294BR06 1000

BR02 1794

BR05 1469

Mean = 7.68LSD 0.05 = 2.09

Mean = 1.96 LSD 0.05 = 1.51

CIAT 36061

MX02 03641

Acknowledgements