Development of productive multi-viral disease-tolerant bivoltine silkworm breeds of Bombyx mori (Lepidoptera: Bombycidae)

Bombyx mori densonucleosis (BmDV), infectious flacherie (BmIFV) and nuclear polyhedrosis (BmNPV) viruses inflict huge losses in sericulture. The study was envisaged to develop productive bivoltine silkworm hybrid, tolerant to these viruses, employing marker-assisted breeding. One hundred and twenty diverse bivoltine silkworm breeds, B. mori L. (Lepidoptera: Bombycidae) in India were screened against BmDV, BmIFV and BmNPV. Eight SSR markers were identified with distinct amplification profiles between virus-tolerant and susceptible populations. Two specific populations derived from the bivoltine silkworm breeds-HBM10 and PAM117-exhibited multi-viral tolerance (PAM117: 36-67%; HBM10: 24-65%) and these lines were designated as PAM117-MVT and HBM10-MVT. The resultant foundation cross (HBM10-MVT x PAM117-MVT) showed 37% enhanced survival (BmDV: 71-75%, BmIFV: 71-74% and BmNPV: 71-72%) over the parental stocks. A productive and multi-viral-tolerant bivoltine double hybrid (RDIN1) was developed by crossing with productive foundation cross (CSR52 x CSR27). The rearing and reeling performance of RDIN1 {(CSR52 x CSR27) x (HBM10-MVT x PAM117-MVT)} was on par with the popular bivoltine double hybrid {(CSR2 x CSR27) x (CSR6 x CSR26)} across the locations. The identified SSR markers could be utilized to develop robust and resilient silkworm hybrids for commercial exploitation.