Genetic analysis of grain weight in wheat

The reciprocal monosomic analysis (RMA) technique of intervarietal chromosome manipulation was used to investigate the genetic control of grain weight in two varieties of wheat (Spica and Chinese Spring). The method enabled major genetic differences between the two varieties for this quantitative character to be assigned to individual chromosomes. The RMA was extended by the extraction of reciprocal disomic F 3 families, of which individual ears were analysed at maturity for grain weight at each position within the ear. Chromosomes 1A, 1D and 7A of the large-grained parent, Spica, increased grain weight relative to the homologous chromosomes of the small-grained parent, Chinese Spring. The effect of chromosomes 1D and 7A were proportionately similar throughout the ear, while that of 1A was disproportionately greater in the distal florets of each spikelet. None of these differences involved simultaneous effects on grain number and thus could be considered to be specific genetic effects on grain growth.