Interpreting Cultivar × Environment Interactions for Yield in Upland Rice

Many morphological and physiological traits have been suggested as potential mechanisms of cultivar differences in rice (Oryza sativa L.) drought tolerance, but few data are available to link those traits to variation in grain production in water‐limited field environments. We evaluated 45 rice cultivars in managed stress environments to relate cultivar × environment (C × E) interaction for yield to specific putative drought‐adaptive mechanisms. Cultivars were sown in aerobic (nonflooded) fields across three seasons, under a range of irrigation systems, to generate nine contrasting environments. Data were collected on yield, plant height, maturity, leaf area, relative water content (RWC), epidermal conductance, root pressure, canopy temperature (CT), and chlorophyll content. Mean grain yield ranged from 0.6 to 2.0 Mg ha−1 across environments. Correlations between grain yields measured in different environments ranged from −0.14 to 0.86. Pattern analysis revealed different cultivar responses in environments with continuous stress or stress during grain filling compared with environments with ample water or environments with adequate drip irrigation. Traits related to C × E interaction scores for yield included anthesis date, leaf percentage fresh weight (%FW), root pressure, leaf area, and rooting depth. Early maturity was found to be advantageous under drought, even when stress was applied at specific developmental stages for each cultivar. Separate pattern analyses for yield components confirmed that cultivar groups that interacted differently with environments for spikelet fertility and thousand‐grain weight (TGW) also differed in specific drought‐related traits.