Genetic Control of Quantitative Variation in Phaseolin Seed Protein of Common Bean

Three populations of near-homozygous inbred backcross lines of common bean ( Phaseolus vulgaris L.) were produced using ‘Sanilac’ as the recurrent parent and 3 donor parents, ‘BBL 240’, 15R-148, and ‘Swedish Brown’. The method for producing inbred backcross lines included 2 successive backcrosses to the recurrent parent followed by 3 or 4 generations of self-fertilization using single seed descent. There was no conscious selection during the backcrossing or selfing stages. Lines were grown in the Held and analyzed for seed protein content, percentage of protein, seed yield, and seed size. In each population, the frequency of lines recovered having enhanced levels of phaseolin (compared to ‘Sanilac’) suggested that one or a few major genes (effective factors) for phaseolin had been contributed by the donor parent. In population 2, derived from ‘Sanilac’ crossed to ‘BBL 240’, there was evidence for possible linkage between enhanced phaseolin and the gene(s) controlling the electrophoretic banding pattern of the phaseolin polypeptide subunits. The nonprotein portion of the seeds of these lines was also less than that of the recurrent parent, resulting in generally smaller seeds. In contrast, some families in population 6 (donor 15R-148) having enhanced phaseolin also showed increased levels of the nonprotein constituents of the seed. Population 8 (donor ‘Swedish Brown’) was unique since lines with enhanced levels of phaseolin were recovered although the donor parent had a low phaseolin concentration (phaseolin/100 g flour) but large seeds with a high concentration of the nonprotein fraction. These results show that breeding lines with increased levels of phaseolin seed protein can be produced either directly by increasing the phaseolin concentration or indirectly by decreasing the nonprotein fraction of seed.