Pattern of genetic variability for morphological and productive traits in wheat genotypes having differential photothermo response

Forty wheat (Triticum aestivum) genotypes were classified on the basis of their photothermal response into five groups. In the high temperature-and photo period responsive genotypes, sowing under high temperature and long days of October caused reduction in number of days to heading, tillers/plant, plant height, spikelets/spike, grains/spike, and grain yield/plant, but such reduction was not observed in the photothermo-non-responsive genotypes. Maximum resolution of variability for tiller number and plant height was recorded in December sowing among all the genotypes. However, maximum variability for other traits wasexpressed differently among genotypes of different groups in different environments. The genotypes possessing high degree of thermo tolerance may be used by plant breeders in hybridization to develop heat tolerant strains or may be directly promoted as cultivar.