The relationship between the Rht1 and Rht2 dwarfing genes and grain weight in Triticum aestivum L. spring wheat

The study was carried out in the first year on samples of random F5 lines, uniform in height and in heading date, of three crosses between semi dwarf spring wheat cultivars (Triticum aestivum L.), differing in grain weight and in their Rht gene. In the second year only the progenies of the early heading F5 lines were studied. All the material was grown in the absence of lodging. The culm-length genotypes of the different lines were identified by test crosses and by a seedling GA response test. No differences in grain weight were found between the two semi dwarf genotypes (Rht1Rht1rht2rht2 and rht1rht1Rht2Rht2). The tall genotype (rht1rht1rht2rht2) was significantly higher in grain weight than the two semi dwarf genotyes and the grain weight of these genotypes exceeded markedly the grain weight of the dwarf genotype (Rht1Rht1Rht2Rht2). These genotypic effects were independent of differences in plant height, heading date or number of grains per spike.