Physiological and biochemical responses of garden pea genotypes under reproductive stage heat stress.

High temperature causes several morphological, physiological, and biochemical changes in crop plants, and garden pea is highly sensitive to a higher temperature than other legume crops. This study assessed garden pea genotypes' physiological and biochemical responses during a reproductive stage in regular and heat stress season at the Division of Vegetable Science, Indian Agricultural Research Institute, New Delhi (India). Forty-five garden pea genotypes, including 15 tolerant, 15 moderately tolerant, and 15 susceptible genotypes, were analyzed for three physiological, six biochemical, and 11 quantitative morphological traits under regular and heat stress seasons. Our results showed a considerable decrease in leaf water content, greenness index, and membrane stability index in heat stress season and a substantial increase in malondialdehyde, hydrogen peroxide, and antioxidant enzymes in heat stress season compared to the regular season. The 15 heat-tolerant genotypes showed a significant increase in antioxidant enzymes compared to the 15 heat-susceptible genotypes, which impart thermotolerance by scavenging reactive oxygen species generated in high-temperature stress conditions. Further, correlation and biplot analysis of morpho-physiological and biochemical traits indicated that physiological and biochemical traits were important in determining yield and related traits under heat stress conditions in garden pea genotypes. Thus, estimating critical physiological and biochemical traits could facilitate in differentiating thermotolerant genotypes from susceptible genotypes in garden peas and aid in heat-tolerant breeding programs of similar cool-season legume crops. [ABSTRACT FROM AUTHOR]