A study of grain number in two contrasting wheat cultivars

Abstract

The origin of the grain number difference between two contrasting wheat cultivars (WW 15, Mexican semidwarf; Timgalen, Australian) was studied in terms of (i) the production and distribution of dry matter during the pre-anthesis development of the ear; (ii) the number of florets initiated; and (iii) interaction between grains during grain set. Grain yield was much more closely related to harvest index than to total dry weight, and harvest index appeared to be largely a function of the number of grains produced per unit area. The difference in grain number between the cultivars bore no relation to the number of florets initiated by them. Nor was the inhibition of grain set in the distal florets of spikelets by rapid growth of grains in basal florets involved. Large differences in grain number occurred between the cultivars where there was no detectable difference between them in the production and distribution of dry matter during pre-anthesis ear development, i.e. the semidwarf cultivar was superior in setting grains for some reason other than the pattern of distribution of dry matter between grain and straw.