Evaluation of yield components and heat susceptibility of pakistani wheat (TRITICUM AESTIVUM L.) germplasm subjected to induced terminal heat stress

A set of 205 Pakistani wheat genotypes was evaluated to access the endogenous potential for heat tolerance and agromorphological genetic diversity in wheat population subjected to induced terminal heat stress. About 10 out of 21 agromorphological traits, showed higher coefficient of variation (CV%) in comparison to control, which was directly associated with extent of variability in subjected population. Various traits showed a strong positive correlation in case of treatment and control. First two axes of bi-plot, F1 and F2 of principal component, PC1 as well as PC2 explained 17% and 12% for year 2017-18, 16% and 15% for year 2018-19, as well as 14% and 12% variability under control conditions respectively. Total of 8 genotypes showed heat susceptibility index (HSI≤ 0.5), hence designated as highly heat tolerant (HHT) genotypes. These genotypes also showed ≤ 20% cumulative reduction in 1000-kernel weight in comparison to control. On the bases of green leaf retention (GLR) scale, population was classified into 4 categories i.e., 11, 11% resistant (R), 48, 41% moderately resistant (MR), 22, 41% moderately susceptible (MS) and 19, 7% susceptible (S) during year 2017-18 and 2018-19 respectively. This data will be used to perform genome wide association studies (GWAS) to identify QTLs associated with heat stress tolerance.