2023 Volume 31 Pages 35-40
Silk is attracting interested not only as a material for clothing but also as a medical and industrial material. Development of higher strength silk is anticipated for all applications. A high-strength silk thread producing silkworm strain “MC502” has been developed through selective breeding, whereas improving the raw silk yield is necessary to support its practical use. Earlier studies have demonstrated that “MC502 × J137” can improve the raw silk yield while maintaining high strength characteristics of MC502, although the effects of reverse crossbreeding “J137 × MC502” on cocoon thread character are not clear. Therefore, we investigated differences in rearing duration, cocoon thread character, and raw silk yield, if any, between forward and reverse crossbreeding of MC502 and J137. No significant difference was found in the rearing duration or reeling test score, between forward and reverse crossbreeding. Moreover, the raw silk yields were similar. Depending on the rearing year, some differences in cocoon shell weight and strength of the raw silks were found between forward and reverse crossbreeding. These differences were few and slight: both raw silks retained their high-strength character. Therefore, no marked difference in cocoon thread character was found between the forward and reverse crossbreeding of MC502 and J137.
