Studies on the isolation of promising polyvoltine breed ND7 and its F1 hybrid performance with productive bivoltine races.

摘要

A breeding programme was initiated during August-September, 2003 utilizing one polyvoltine silkworm breed, BL67. During the maintenance of BL67, some larvae with prominent eye spots on second thoracic segment were observed and separated. By following directional selection for subsequent generations, the line, ND7 was isolated and stabilized. The F1 hybrid performance of ND7 was evaluated at 7th generation by crossing with eleven bivoltine silkworm breeds. One hybrid, ND7 x CSR2 showed its superiority for several economic characters such as fecundity, pupation rate, cocoon yield/10 000 larvae by weight, filament length and raw silk %. The new hybrid exhibited the highest average evaluation index value and recorded evaluation index value >50 for nine out of ten characters. Ten hybrids revealed higher magnitude of hybrid vigour for cocoon yield/10 000 larvae by weight, cocoon weight, cocoon shell weight and reelability. Advantages of commercial exploitation of ND7 x CSR2 have been discussed.