Shardendu Kumar Singh, Mississippi State Univ, Dept of Plant and Soil Sciences, 117 Dorman Hall, Box 9555, Mississippi State, MS 39762 and K.Raja Reddy, Mississippi State University, Department of Plant and Soil Sciences, 117 Dorman Hall, Box 9555, Mississippi State, MS 39762.
Drought is the major abiotic stress factor that causes extensive losses to agriculture production worldwide. Developing simple and accurate tools to identify genetic variability among cultivars for drought tolerance will be useful in crop breeding programs. The objective of this study was to evaluate the dynamics of leaf photosynthesis, chlorophyll fluorescence and water use efficiency of cowpea cultivars for drought tolerance. An experiment was conducted using fifteen cowpea cultivars seeded in 12-L pots, filled with fine sand, and irrigated with half-strength Hoagland’s nutrient solution from emergence to 34 days after sowing (DAS). Thereafter, one set of plants continued to receive optimum water and the other set received no water for another 20 days. Photosynthesis (A), water use efficiency and fluorescence (Fv’/Fm’) parameters along with soil water content (SWC) were measured. Soil water content during the drought stress period varied from 0.003 to 0.045 m3 water m-3 soil. Photosynthesis and Fv’/Fm’ declined linearly with decreasing SWC in all cultivars, and stomatal conductance showed a non-linear reduction with SWC. Maximum photosynthesis and Fv’/Fm’ at optimum SWC, and slopes of A and Fv’/Fm’ with SWC varied among cultivars. Similarly, intrinsic water use efficiency, calculated as the ratio of assimilation rate over stomatal conductance and the inverse of (ci/ca)min, an indicator of maximum water use efficiency, also varied among cultivars. Cumulative drought response index, CDRI, (unitless), of each genotype calculated as the sum of four individual stress response indices derived from photosynthesis and photochemical parameters and two water use efficiency parameters, was used to group genotypes for drought stress tolerance. Even though genotypes can be separated based on photosynthesis and photochemical and water use efficiencies, the CDRI of photosynthesis and water use efficiency, we found no significant correlation between these parameters indicating tolerance mechanisms in assimilation and water use processes operate differently.
See more of Graduate Student Oral Competition--Crops
See more of The 2007 SAAS Convention
