Manifestation of the dilute black (bd) mutation and constitution of the bd locus in Bombyx mori

A Bombyx mori mutant named dilute black (bd), which has the multiple alleles bd, bd^sw and bd^f, each affecting both the larval body color and female fertility, was investigated for the manifestation of these pleiotropic traits by mating experiments with the k40, k42 and k452 strains harboring bd, bd^sw and bd^f, respectively, in the heterozygous state. It was shown that bd, bd^sw and bd^f were strong, intermediate and weak, respectively, in the degree of larval body color. On the other hand, bd and bd^sw were identical to each other in terms of female sterility, whereas bd^f was as fertile as normal. The degree of body color and the female sterility showed a high parallelism with each other. On the basis of these results, we proposed that the bd locus consists of closely linked two domains, one for the larval body color and the other for the female fertility.