LATE PLANTING INDUCED HEAT STRESS TOLERANCE IN WHEAT

Wheat crop with late planting is rapidly subjected to stress due to high temperature which severely affects crop growth, grain filling, and eventually grain yield. Present studies aim to recognize the heat stress tolerant wheat genotypes by using stress selection indices, principal components, and biplot analyses. Hence, 24 wheat genotypes (including six advanced lines and 18 commercial wheat cultivars) were evaluated through genotype by environment interactions. Wheat genotypes were grown in a randomized complete block design with a factorial arrangement under normal (non-stress) and late (stress) planting environments with three replications. Stress selection indices i.e., tolerance index (TOL), mean productivity (MP), stress tolerance index (STI), trait stability index (TSI), trait index (TI), and the principal component (PCA) and biplot analyses were used to assess the response of wheat genotypes. Significant (p<0.01) variations were observed between environments, while genotypes and genotype by environment interactions revealed significant (p<0.01) differences for the majority of the traits. Because of reduced heat stress emphasis and sufficient growth period, genotypes with optimum planting performed better compared to late planting. Under the late planting environment, cultivars Khaista-2017, Shahkar2013 and Zincol-16 performed better for grain yield and its components. With non-stress and stress (Yn and Ys) conditions, the grain yield was found significantly and positively correlated with stress selection indices i.e., MP, STI, TSI, and TI whereas the yield relationship was negative with TOL. Genotypes Zincol-16, Pakistan-13, and Khaista-2017 were identified as stress-tolerant and high yielding under both environments indicating their potency to tackle late planting and heat stress. Traits with indirect positive effects could be used as selection criteria, and the promising genotypes could be used as a source population in the development of heat stress-tolerant wheat cultivars in the future breeding program.