Relationship between time of anthesis and grain yield of wheat genotypes with differing developmental pattern

This paper reports studies of the effects of time of planting and genotype on wheat grown with and without irrigation in Queensland. Under irrigation, and in the absence of frost damage, the grain yield of a number of semidwarf wheat genotypes was highest when anthesis occurred in midwinter. There was a linear decline in grain yield with departure from this anthesis period, associated with rising evaporative demand and daily mean temperature. Genotype variation in this yield pattern was due to different growth durations and in particular to the leaf areas developed by anthesis, which were often limiting yield especially in very early planting of quick genotypes. Under dryland conditions similar patterns of grain yield variation with anthesis date occurred, although the genotype variation about this pattern depended upon the interaction between growth duration and leaf area development on the one hand, and water use on the other. These results suggest that some consideration be given to altering the agronomy, in regions of low frost risk, to take advantage of the higher yield potential associated with midwinter anthesis dates. The effects of growth duration, anthesis date and environment could be integrated into a yield index of the form Grain yield index = a + b(T/E0) x (l/Tm), where a and b are constants, T, E0 and Tm are transpiration (mm), pan evaporation (mm) and mean daily temperature (¦C) respectively, all estimated or measured within ¦ 10 days of anthesis (r2 = 0.801, n = 112). The regression slope was constant across sites, times of planting and irrigation treatments for closely related semidwarf genotypes, but was significantly lower for a group of taller wheats tested. These groupings were associated with differences in grain number per mZ. The similarity between this yield index and the crop growth index of de Wit suggests that grain yield in wheat is closely linked to the growth potential over a short period around anthesis.