Grain yield increase in recent argentine wheat cultivars

This study analyzes differences in potential yield among six semidwarf awned spring bread wheat (Triticum aestivum L.) cultivars recently selected in Argentina. Yield was considered as the product of number of grain per square meter (NG) and weight per grain. The NG was analyzed in terms of (i) duration of the inflorescence growth period (excluding grains), (ii) crop growth rate during that period, (iii) partitioning of crop dry matter to spikes during the same period, and (iv) grain/spike weight ratio (i.e., number of grains per gram of spike). The data were obtained from two field experiments in the Province of Buenos Aires. Grain yield (range: 453-689 g m(-2)) was related more to NG (range: 13.3-21.3 x 10(3) grain m(-2)) than to weight per grain. Duration of spike growth period was the same (27 d) for all cultivars, During this period, intercepted photosynthetically active radiation, radiation-use efficiency (mean: 2.7 +/- 0.28 g MJ(-1)), and crop growth rate (mean: 26 +/- 2.5 g m(-2) d(-1)) were similar for all the cultivars examined, Differences among cultivars in partitioning to spikes (ranges: 28-34%) were significant. The NG, however, was not related to partitioning to the spike. There were clear differences among cultivars in the grain/spike weight ratio (range: 61-106 grain g(-1)); NG was more closely related to this ratio (r = 0.96, P < 0.01) than to dry weight of spikes at the end of their growth period (r = -0.30). increments in potential yield by means of high grain/spike weight ratio were not previously reported and may be a path to future potential yield improvements.