Development of PolyvoltinexBivoltine Hybrids of Mulberry Silkworm, Bombyx mori L. Tolerant to BmNPV

In the silkworm rearing, the usage of commercial silkworm hybrids resistant/tolerant to silkworm diseases is economical and better option particularly in tropical countries, where inadequate disinfection methods are practiced. Among the major silkworm diseases, grasserie caused by Bombyx mori Nuclear Polyhedrosis Virus (BmNPV) is controlled by polygens. In the present study, an attempt was made to develop BmNPV tolerant polyvoltine x bivoltine hybrids by utilizing newly evolved BmNPV tolerant polyvoltine breeds viz., AKP 1, AKP 2 and AKP 3 as lines and bivoltine breeds viz., AKB 6, AKB 7 and AKB 8 as testers by employing LinexTester analysis. Nine hybrid combinations were compared with the control hybrids viz., Pure MysorexCSR 2 and APM 1xAPS 8. Total score of positive traits of Specific Combing Ability (SCA), mid Parental Heterosis (MPH) and Better Parent Heterosis (BPH) was observed maximum in case of AKP 1xAKB 6 with 20 fallowed by AKP 1xAKB 8 (19), AKP 2xAKB 7 (13), AKP 3xAKB 6 (13). Least total score was observed in the case of AKP 1xAKB 7. Based upon the total scores (SCA, MPH and BPH), over dominance and E.I values, AKP 1xAKB 6 and AKP 1xAKB 8 were identified as promising tolerant hybrids against BmNPV with productive merits. These tolerant hybrids can be suggested to the farmers for utilization after conducting large scale trials.