Response Estimation of Wheat Synthetic Lines to Terminal Heat Stress Using Stress Indices

Twenty eight synthetic wheat lines were evaluated for terminal heat tolerance by normal (non-stress) and late (stress) planting in field in randomized block design with three replications for two crop seasons; 2008-09 and 2009-10. The genotypes differed significantly for thousand grain weight in non-stress and stress conditions. The stress susceptibility and tolerance indices were calculated for thousand grain weight and genotypes differed significantly for stress indices also. The stress tolerance indices; Stress tolerance index, Geometric mean production and Mean production had significant positive correlation with thousand grain weight in non-stress and stress conditions. The first two principal components explained more than 89 and 98% of variation during two crop seasons respectively. The study using bilpot analysis revealed that stress tolerance indices can be selection criteria for identification of tolerant genotypes. Using three dimensional plot, the genotypes which performed well in both environments or in one of the environments only or in none of the environments were identified. The synthetic wheat lines S9, S37, S44 and S57 had high thousand grain weight with heat tolerance during both years and genotypes S8, S22, S23, S49 and S77 had poor performance in both environments.