Heat and photothermal indices and their relations to phenology in wheat

Thirty wheat varieties (10 varieties each of early, medium and late maturing groups) were sown on November 10, 1988; November 30, 1989 and December 20, 1990 with three replications in randomized block design. Observations on 10 randomly selected plants in each plot were recorded for phenophases, growing degree-days summations, and photothermal units. The duration from commencement of crop emergence to flowering can best be explained by photothermal units for different genotypes except cultivars WH 157 and HD 2122. On the contrary, the duration from flowering to physiological maturity is best explained by the number of degree-days in all the genotypes irrespective of their maturity groups. The varieties WH 157 and HD 2122 may be recommended through out the globe provided the temperature is not the limiting factor.