Absence of hybrids between the domesticated silkmoth, Bombyx mori, and the wild mulberry silkmoth, B. mandarina, in natural populations around sericulture farms

Abstract

The domesticated silkmoth, Bombyx mori, and the wild silkmoth, B. mandarina, are close relatives. Fertile hybrids can form by the mating of female moths of B. mori with male moths of B. mandarina. Recent studies, however, have found no gene flow from domesticated silkmoths into natural populations. Here, we directly analyzed the rate of interspecific hybridization in conventional sericulture by examining the mitochondrial genotype of silkmoths caught around sericulture farms. Results showed that all of the 3,750 moths had B. mandarina-type mitochondrial genomes; there were no F₁ hybrid moths. This result was supported by experiments showing that no moths emerged after 2,964 F₁ larvae had been released on the ground close to a mulberry tree. These results indicate practically no genetic introgression from B. mori to B. mandarina, therefore suggesting that transgenic silkworm rearing in sericulture farms does not have adverse effects on biological diversity through hybridization.