Interrelationships among different grain characteristics of wheat grown under optimum and late sowning date conditions in the Eastern Indo-Gangetic plains of India

Wheat growth has been severely affected by increases in global temperature. The Eastern Indo-Gangetic Plains of India face similar constraints due to the traditional wheat–rice cropping system where wheat planting is often delayed leading to high temperature induced terminal heat stress. Grain characters like grain length, width, area along with starch synthesis are affected severely during heat stress. Considering the importance of grain traits, we screened the response of 55 wheat genotypes under terminal heat stress conditions to ten grain characteristics. We found that the means of all the grain traits were reduced in heat stress conditions. The effect of heat stress shows a significantly reduced grain width and perimeter, but the extent of damage is less on different grain starch characteristics e.g., grain starch area (GSA), grain starch length (GSL) and grain starch volume (GSV). Stepwise multiple regression analysis revealed that grain starch area and grain volume are the best predictors of yield under optimum sowing date conditions whereas, grain width is the best predictor under late sowing date conditions. Interrelationship studies among ten grain characters showed that the genotypes with higher levels of grain starch characteristics (GSA, GSL and GSV) in combination with the five grain size characters (grain length, grain width, grain perimeter, grain area, A/B-type starch granules) under late sowing date conditions should be promoted for the cultivation of wheat in heat stress prone areas. The present study identified and recommends some heat tolerant wheat genotypes in terms of higher yield and grain starch characteristics namely, CRPW-33, CRPW-17, CRPW-12, CRPW-126 and CRPW-21