Physiological Responses and Yield Component Changes of Winter Wheat Genotypes Under Irrigated, Terminal Drought, and Rainfed Conditions.

Drought conditions occur frequently in southeastern Idaho due to low rainfall during spring and summer, and wheat production in this area is largely affected. However, wheat yield varies greatly between varieties under different water regimes. The yield differences between genotypes could derive from their various physiological traits. Investigating these traits may help us identify plant traits contributing to grain yield, and improve grain yield under low water availability. The objective of this study were to evaluate yield performance in response to different water regimes, and identify physiological traits contributing to grain yield and yield components. Drought tolerant and susceptible varieties and breeding lines were selected based on yield performance of previous years. Experimental plots were established at Rockland (rainfed) and Aberdeen (irrigated and terminal drought), ID. Irrigation was applied throughout the growing season for the irrigated field, whereas irrigation was withheld after the heading stage in the field of terminal drought. Post-anthesis canopy temperature, and leaf gas exchange and leaf senescence of flag leaf exhibited significant differences between genotypes and environments. Grain yield also differed between genotypes and environments, and the yield differences attributed to various physiological characteristics and yield components.