ASSESSMENT OF THERMOTOLERANT BIVOLTINE SILKWORM BREEDS THROUGH BIOCHEMICAL AND MOLECULAR RESPONSES OF SERINE PROTEASE INHIBITORS AND PROPHENOLOXIDASE CHALLENGED WITH Beauveria bassiana (Bals. - Criv.) Vuill
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Date
2022-03-29
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University of Agricultural Sciences GKVK, Bangalore
Abstract
study was conducted to assess the performance of thermotolerant bivoltine silkworm breeds against Beauveria bassiana infection by understanding the ctivities of serine protease inhibitors (SPI) and prophenoloxidase (PPO) in relation to susceptibility vis-a-vis resistance of silkworms to the fungus, during 019-2021 at the Department of Sericulture, UAS, Bangalore. The B. bassiana isolate used in the study was originally collected from Shidlagatta in Karnataka nd named as SHDL. In-vitro assessment of B. bassiana protease showed highest subtilisin-like (Pr1) activity than trypsin-like (Pr2) activity in both intracellular nd extracellular fractions. Standardization of working protocol for determining the SPI and PPO activities revealed that succinyl-(alanine) 2- prolinephenylalanine-p-nitroanilide and DOPA to be better substrates, respectively. Upon injection of extracellular fraction of B. bassiana protease to ten ilkworm breeds viz., B1, B2, B4, B6, B8, APS12, APS45, CSR2, CSR4 and Pure Mysore, B1 and B6 breeds recorded highest SPI activity both in the cuticle nd the haemolymph. B1 and B2 breeds exhibited highest PPO activity in the cuticle, whereas its activity in the haemolymph was highest in B4 and CSR2 reeds. Phenotypic performance of the breeds under high temperature and fungal stress conditions showed that, the thermotolerant breeds B1 and B4 thrived ell with respect to both survival and quantitative parameters under both the stresses. The expression of BmSPI38 and BmPPO1 genes in B1, CSR4 and Pure ysore showed strong expression of BmPPO1 gene in B1 breed than the other two. Further, prophenoloxidase gene expression markedly corresponded to esistance of silkworm breeds to B. bassiana inoculation. Thus, the thermotolerant breed B1 could be dual stress resistant as revealed by SPI and PPO ctivities, phenotypic performance and immune genes expression under B. bassiana infection