Monday, November 5, 2007
63-6

Screening for Tolerance to Waterlogging in Brachiaria Hybrids.

Idupulapati M. Rao, Joisse Rincón, García Ramiro, Jaumer Ricaurte, and John Miles. International Center for Tropical Agriculture (CIAT), 7343 NW 79th Ter., Medley, FL 33166-2211

In the tropics, Brachiaria pastures during the rainy season occassionally face waterlogging conditions that severely limit pasture productivity and animal performance. Waterlogging or flooding reduces the availability of soil oxygen to the plant. A pot experiment was conducted to determine differences in tolerance to waterlogging among 60 Brachiaria genotypes including 48 hybrids of BR04NO series, 3 parents and 9 checks. Waterlogging treatment was imposed by applying excessive water to the pots (5 cm over soil surface). The trial was planted as randomized complete block with 3 replications. Plants grew for 50 days under 100% field capacity of soil moisture. Leaf chlorophyll content and photosynthetic efficiency were measured at weekly intervals for 3 weeks on a full expanded young leaf marked at the initiation of waterlogging treatment. After 21 days of waterlogging, green leaf biomass, total shoot and root biomass, root volume and root length and mean root diameter of adventitious roots were measured. At 21 days after waterlogging, several hybrids were dead. Results on adventitious root development during waterlogging indicated that this could be a strategy to overcome hypoxia but not all genotypes seem to use this as a mechanism. Significant genotypic variability in green leaf biomass was observed after 21 days of waterlogging. Two checks, B.dictyoneura CIAT 6133, BR02NO/1485, were outstanding in green leaf biomass production. Among the BR04NO series of hybrids tested, three hybrids BR04NO/3069, BR04NO/3207 and BR04NO/2774 were superior in their production of green leaf biomass than the others hybrids. These three hybrids were superior in their tolerance to waterlogging based on greater values of green leaf biomass production and leaf chlorophyll content and lower values of dead leaf biomass. These three plant attributes could serve as criteria for selection for waterlogging tolerance in Brachiaria. This work is partially supported from the funds of Grupo Papalotla, Mexico.