Inheritance and characteristics of a novel low-temperature sensitive gray-egg mutation in Bombux mori

A recessive mutation affecting the eggshell character was found spontaneously in some strains stocked in Kyushu University. It had characteristics of the so-called “gray egg”, wherein the eggshell is opaque or white to various degrees. This trait was expressed only when female pupae were chilled at 8 to 10°C for 24hr (usually to suppress pupal-adult development). Control animals continuously kept at 25°:C did not produce such eggs. The ratio of cold-induced gray eggs to the total eggs was about 7% per batch. Linkage analysis using one the sensitive strains (cll) showed that the gene controlling this character was linked to the ok gene which belongs to the 5th linkage group. The novel mutant gene was named the “low-temperature sensitive gray-egg” with the gene symbol tsg.