Heritable Variation in a Polypeptide Subunit of the Major Storage Protein of the Bean, Phaseolus vulgaris L.

Electrophoretic analysis of the major seed protein, G1 globulin, from four strains of Phaseolus vulgaris L. revealed a three-banded pattern for two strains having a high methionine content (BBL 240 and PI 302,542). The other two strains (PI 207,227 and PI 229,815) known to have a lower seed methionine content, had a two-banded subunit pattern for the G1 globulin. Analytical ultracentrifugation confirmed that globulin from the two-banded strains underwent pH-dependent reversible dissociation similar to that previously found for a three-banded cultivar; additionally, the protomer molecular weight showed that three subunits of about 50,000 molecular weight each were present in the G1 globulin of the two-banded strain. Gel patterns of G1 globulin from the two strains used as parents, BBL 240 and PI 229,815, showed differences in the largest subunit, which appeared as either a 53,000 molecular weight polypeptide known to be present in the three-banded strain, or as a shorter polypeptide having a molecular weight close to 47,000. Analysis of G1 protein from portions of single hybrid seeds showed a banding pattern intermediate between the two- and three-banded types. The subunit pattern from all seeds with intermediate-banded parents segregated in a manner consistent with that expected for control of the polypeptide by a single Mendelian gene. The remaining portions of the seeds were grown to confirm that they represented true crosses. The procedures used are essentially nondestructive, and can be used as a basis for selecting seeds having different protein characters.