Activity of Peroxidase and Catalase Enzymes in Thermotolerant Silkworms Bombyx mori. L. in Response to Beauveria bassiana (Bals. - Criv.) Vuill. Infection

With an intention to understand the mechanism of dual stress tolerance, a study on antioxidant enzymes activity in thermotolerant bivoltine silkworm breeds and hybrids under Beauveria bassiana infection was conducted at the Department of Sericulture, UAS, GKVK, Bengaluru during 2021-22. Thermotolerant bivoltine breeds viz., B1, B4 and B8 and their hybrids with CSR4 along with Pure Mysore as a muscardine resistant and CSR4 as a muscardine susceptible breeds were used in this study. All the breeds and hybrids were raised following CRD experimental design and were inoculated with B. bassiana immediately after 4th moult and another group was reared under normal condition. The haemolymph was collected from these breeds and hybrids at 24, 48, 72, 96 and 120 hours post inoculation (hpi) from both the batches and utilized for the estimation of total protein content and peroxidase and catalase enzyme activities in the haemolymph. The total protein content increased from 24 h to 120 h in all the breeds and hybrids under both control and muscardine inoculation, but being lesser under inoculation. The peroxidase activity was found higher in B1 breed from 48 hpi to 120 hpi under both control and inoculated conditions, but decreased at 24 hpi under inoculation. Catalase activity was enhanced at all time intervals under inoculated conditions in Pure Mysore, B1, B4 and B8 breeds and B4×CSR4 hybrid compared to control condition. Thus increased catalase activity in B1 and B4 breeds and decreased peroxidase activity in B1 breed could be associated with their better performance for survival and economic parameters under inoculated condition.