Abstract: 【Aim】 Re-nd, a non-diapause red egg mutant of the silkworm, Bombyx mori, is a new egg color mutant. It was obtained by mutagenesis of the C108 strain induced by the chemical mutagen N-methyl-N-nitrosourea (MNU), belonging to serous membrane mutation. This study aims to analyze the mechanism of mutant phenotype by traditional genetic methods, so as to lay a foundation for further cloning, functional research and application of the mutant genes of Re-nd. 【Methods】 The hybridizing, sib mating and backcrossing between non-diapause mutant Re-nd and the wild-type diapause bivoltine Dazao strain and non-diapause polyvoltine N4 strain of B. mori, respectively, and the genetic analysis were carried out. Meanwhile, the hybridizing, sib mating and backcrossing between Re-nd and diapause egg color mutants with the known mutants such as white egg mutant w-2, peach red eye white egg mutant pe and red egg mutant re of B. mori, respectively, and the genetic analysis were also carried out. 【Results】 The results showed that the non-diapause eggs of F₁ hybrids of Re-nd with Dazao and N4 were both in light red. The non-diapause eggs of F₂ generation of sib mating were in red, light red and light yellow with the ratio of the number of red eggs (including light red eggs) to the number of light yellow eggs basically conforming to 3∶1. The nondiapause eggs of backcross B1 generation were in red and light yellow, with the ratio of the number of red eggs to the number of the light yellow eggs being basically consistent with 1∶1. The diapause eggs of F₁ hybrids of Re-nd with w-2 and pe were in light brown. The diapause eggs of F₂ hybrid of Re-nd with w-2 were in normal dark brown, light brown, yellow and light yellow with slightly red, while the non-diapause eggs of F₂ hybrid were in red, light yellow with slightly red, orange-yellow and light yellow. The F₂ hybrid eggs of Re-nd with pe were all diapause eggs in normal dark brown, light brown, light yellow with slightly red and red. The hybrid diapause eggs of Re-nd with re in F₁were in light brown, and those of in F₂ were all diapause eggs in normal dark brown, light brown and red. The diapause eggs in re parents were in red, and no new egg color separation was found in the hybrid eggs of Re-nd with re in F₂. 【Conclusion】 Through the hybridization and genetic analysis, it was confirmed that Re-nd mutant is an independent dominant inheritance, and the mutant gene of Re-nd should be located in the downstream of the mutant genes of w-2 and pe and may be involved in the process of further metabolism of 3-hydroxy-caninuric acid to ommatins at the later stage of ocular pigment biosynthesis, which is different from the wild-type egg pigment metabolism branch.

Key words: Bombyx mori, non-diapause red egg, ommochromes, hybridization, genetic analysis, pigment metabolism