Resistance of silkworm variety resources from Yunnan sericultural areas to Bombyx mori nucleopolyhedrovirus (BmNPV)

ObjectiveThe present study investigated resistance of silkworm variety resources from Yunnan sericultural areas to Bombyx mori nucleopolyhedrovirus(BmNPV) in order to search for disease-resistant materials and breed resistant varieties adapting to local conditions. MethodBmNPV of the same concentration were added into silkworm feed for the 3rd instar larva. BmNPV disease resistance of 200 silkworm varieties(strains) was evaluated. Based on indexes like survival number per day and survival rate at each growth period, BmNPV resistance level of the silkworm varieties in Yunnan seri-cultural areas, morbidity and death regularity, death time of different resistant varieties, and resistance comparison be-tween different strains of the same varieties were analyzed. ResultMediately resistant varieties in Yunnan sericultural areas included 731, 795, 854B, 872A, 966B, B Huangrousejian, P50, Shanhe B, Xuanerjiabai and Zhuyin; susceptible varieties were 955, 242A, 242B, 963B, DW3, Jinxiu A, Jinxiu B, Ri, Yeyi and Yunxia A You. The difference in silk-worm death occured at 96 h post inoculation for resistant varieties while 48 h post inoculation for susceptible varieties. Disease-resistant varieties was 48 h later than susceptible varieties in the emergence of death. For some disease-resistant varieties, the resistance to BmNPV in autumn was weaker than in sprig. There was no significant difference in resistance between A starin and B strain belonging to the same varieties(P>0.05). ConclusionMost varieties of the silkworm resources in Yunnan are mediately resistant to BmNPV. P50 has the strongest disease resistance. When evaluating resistance to BmNPV of unknown varieties, 168 h post inoculation can be consider as a key time point.