Molecular Mapping of D₁, D₂ and ms5 Revealed Linkage between the Cotyledon Color Locus D₂ and the Male-Sterile Locus ms5 in Soybean

In soybean, genic male sterility can be utilized as a tool to develop hybrid seed. Several male-sterile, female-fertile mutants have been identified in soybean. The male-sterile, female-fertile ms5 mutant was selected after fast neutron irradiation. Male-sterility due to ms5 was associated with the “stay-green” cotyledon color mutation. The cotyledon color trait in soybean is controlled by two loci, D₁ and D₂. Association between cotyledon color and male-sterility can be instrumental in early phenotypic selection of sterility for hybrid seed production. The use of such selection methods saves time, money, and space, as fewer seeds need to be planted and screened for sterility. The objectives of this study were to compare anther development between male-fertile and male-sterile plants, to investigate the possible linkages among the Ms5, D₁ and D₂ loci, and to determine if any of the d₁ or d₂ mutations can be applied in hybrid seed production. The cytological analysis during anther development displayed optically clear, disintegrating microspores and enlarged, engorged pollen in the male-sterile, female-fertile ms5ms5 plants, a common characteristic of male-sterile mutants. The D₁ locus was mapped to molecular linkage group (MLG) D1a and was flanked by Satt408 and BARCSOYSSR_01_1622. The ms5 and D₂ loci were mapped to MLG B1 with a genetic distance ~12.8 cM between them. These results suggest that use of the d₂ mutant in the selection of male-sterile line may attenuate the cost hybrid seed production in soybean.