Characterization of seed coat post harvest darkening in common bean (Phaseolus vulgaris L.).

Seed coat post harvest darkening (PHD) represents a problem for producers and consumers of several market classes of dry bean. There are three PHD phenotypes: (1) non-darkening (ND), (2) slow darkening (SD) and (3) regular darkening (RD). The inheritance of PHD was elucidated by evaluating populations derived from crosses among multiple RD, SD and ND genotypes. Results indicate that at least two unlinked major genes control the PHD trait in common bean. Recessive epistasis with three phenotypic classes explains the segregation ratios of populations from crosses between SD and ND parents. One gene, J, is responsible for whether a bean will darken as seeds from plants that are jj do not darken at all. Another gene, sd, influences how quickly a seed coat will darken with sdsd individuals darkening more slowly than those with the dominant Sd allele.