Genetic analysis of the new mutant, translucent Hime'nichi, in the silkworm, Bombyx mori

Abstract

A new translucent mutant silkworm was discovered in the genetic stocks of the univoltine Hime'nichi Japanese race of Bombyx mori held by the National Institute of Agrobiological Sciences. In some egg batches of this mutant, many embryos died immediately after pigmentation. Additionally, larvae died frequently at the 4th and 5th larval stages. These observations revealed the weak constitution of the mutant insect. The degree of the translucency in the mutants was considered intermediate in comparison with other translucent mutants. Interestingly, in addition to mutant progeny resulting from sibmating of mutants, the F₁ generation also segregated several normal phenotypes. Genetic analysis showed that the mutant gene was recessive and different from other translucent genes reported previously. The mutant was given the name, Hime'nichi translucent (ohi). Linkage analysis showed that ohi was linked to the 16th chromosome. The ohi locus was determined to be at the 30.5 cM position using a three-point test with two typical genetic markers, cts and lu, on the 16th chromosome.