Effect of late planting heat stress on membrane thermostability, proline content and heat susceptibility index of different wheat cultivars

Abstract

Four wheat cultivars e.g., Aghrani, Kanchan, CB-30 and Sonora were tested under normal and post anthesis heat stress condition by seeding them on November 30 and December 30 to evaluate the heat tolerance of wheat in relation to proline content. Time to exceed 50% membrane leakage was about four times longer in Aghrani, Kanchan and CB-30 (120-150 min.) and the cultivars were grouped as heat tolerant (HT) than in Sonora (30 min) which considered as heat sensitive (HS). Due to post anthesis heat stress condition the HS cultivar Sonora in comparison to heat tolerant (HT) genotype exhibited larger decrease in kernel proline (47.2%) along with larger increase in flag leaf proline (122%). The heat tolerant cultivars exhibited distinctly higher relative individual kernel dry weight, higher kernel number per spike, higher relative grain yield and low susceptibility index for grain yield under post anthesis heat stress condition compared to heat sensitive cultivar. Strong correlation existed between heat killing time in membrane thermostability test and relative change to normal in proline content (both in flag leaf and kernel) and between heat susceptibility index for grain yield and relative change to normal in proline content.