Limited Transpiration Trait in Crop Plants.

Drought stress is the most important abiotic factor restricting crop productivity throughout the world. Due to limited water availability and economic resources, irrigation is a non-viable substitute for many farmers. A plant trait that might be especially beneficial in drought-prone environments is partial stomatal closure to limit transpiration rate under high atmospheric vapor pressure deficit (VPD) resulting in conservation of soil water.  Water conservation early in the growing season would be especially beneficial to sustain physiological activity during the latter part of the season.  Significant intra- and inter-specific variation in crop species has been demonstrated in their stomatal response under high VPD. Genotypes expressing the limited-transpiration trait (TR) have now been identified in peanut, maize, sorghum, soybean, pearl millet, and wheat.  There is indication that the limited-transpiration traits may be associated with variations in plant hydraulic conductance. Approaches for screening for the trait using chemical inhibitors fed to leaves are being developed to facilitate breeding efforts.  In soybean, advanced breeding lines have already demonstrated superior yield in water-limited environments.