The effects of 'gibberellin-insensitive' dwarfing alleles in wheat on grain weight and protein content.

Three series of near-isogenic wheat lines differing in dwarfing alleles, in the varietal backgrounds of 'Maris Huntsman', 'Maris Widgeon' and 'Bersee', and the F2 grain on intravarietal F1 hybrids, produced with a chemical hybridising agent, were examined for grain size and protein content. Individual F2 grains from Rht1/rht, Rht2/rht and Rht3/rht F1 spikes were classified for Rht genotype by assaying embryo half grains in a gibberellic acid seedling response test, while the remaining half was used for protein determination. Mean grain weight and protein percentage were lower in all homozygous isogenic lines and the Rht/rht F1 hybrids than in the respective tall lines, in an allele dose-dependent manner. In all the hybrids, the Rht genotype of individual F2 grains, which segregated within the spikes of F1 plants, had no significant effects on grain weight or protein. Consequently, the pleiotropic effects of the Rht alleles on these yield and quality components must be attributed to their presence in maternal plant tissues rather than in the endosperm or embryo tissues of individual grains.