Screening Switchgrass for Water Stress Tolerance.

SCREENING SWITCHGRASS FOR WATER STRESS TOLERANCE Mohamed Fahej*, Tanka P. Kandel, and Gopal Kakani Department of Plant and Soil Sciences, Oklahoma State University, Stillwater, OK Abstract Water stress can have a major effect on biomass production. Better understanding of the parameters that correlate with the tolerance to this abiotic stress can help identifying genotypes for high biomass production. The objective of this study is to evaluate growth and physiological parameters and identify switchgrass traits that can contribute to increased water use efficiency. Thirteen genotypes were studied; three lowland (Carthage, Alamo, and Kanlow) and ten upland (Southlow, Cave-in-Rock, Forestburg, Blackwell, Nebraska 28, Shelter, Shawnee, Dacotah, Sunbrust, and WI Ecotype). Seeds were sown in 12 L pots filled with pure sand medium inside greenhouse facility at OSU in Summer of 2009. At 74 days after emergence, two sets of plants were subjected to water stress through automatic drip irrigation system. This was achieved by reducing water supplied to get two levels of water stress (60%WW and 20%WW) of control (well watered plants (WW)). Physiological parameters were measured including photosynthesis, fluorescence, electron transport rate and stomatal conductance using LI-6400 portable photosynthesis measurement system. Multivariate analysis was carried out to identify the tolerant genotypes and traits contributing to tolerance. Total biomass and biomass components of all genotypes were measured at final harvest. Genotypes responded differently to water stress treatments. Water stress had a significant effect on decreasing photosynthesis rate and the decrease was greater in 20%WW compared with 60%WW. Genotypes Carthage (lowland) and Forestburg (upland) had the least decrease in photosynthesis at both 60%WW and 20%WW conditions. In general, biomass and its components decreased with increase in water stress. Exceptions for this included upland genotypes Forestburg, Blackwell, Shelter, Sunburst and WI ecotype. These genotypes exhibited either an increase or minimum decrease in biomass under water stress conditions. Among the various traits evaluated, plant height, stem elongation rate, and photosynthetic and fluorescence parameters were indicative of water stress tolerance. Genotypes and traits identified in this study can be used in breeding programs to improve switchgrass performance under water stress conditions.