Effect of Heat Stress on the Performance of Six Generations of Six Crosses for Different Metric Traits Under Two Different Environments

The present investigation was conducted with an objective to study the impact of high temperature stress on yield and its components for selecting heat tolerant genotypes. Nine genetically diverse homozygous genotypes of wheat, viz., PBW 343, WH 283, WH 542, PBW 435, UP 2565, UP 2425, EIGN1, EIGN8 and Raj 3765, were selected to generate the experimental material which comprised six parental and segregating generations (P1, P2, F1, F2, BC1 and BS1 of BC1). Observations were recorded on 12 morphological traits. Based on generation mean analysis, highly significant differences were found among the generations with respect to all the 12 morphological characters studied in timely and late sown environment. It was observed that the performance was influenced by high temperature under late sown conditions, as evident from the decreasing pattern for all the characters. The duration of linear grain growth was greatly reduced as temperature increased in late sown heat stress condition. Grain growth rate among the parental genotypes was highest in UP 2425 and cross PBW 343 * PBW 435 in both the environments. Based on the mean performance of crosses in normal and late sown conditions, it can be concluded that cross EIGN 1 * Raj 3765 was found best for 1000-grain weight, biological yield and grain yield. Grain growth rate among the parental genotypes was highest in UP 2425 and cross PBW 343 *PBW 435 in both the environments. These offered promise for selection of wheat genotypes possessing inherent mechanisms for tolerance to terminal heat stress