Some thermotolerant bivoltine silkworm breeds tolerate white muscardine diseases caused by beauveria bassiana (bals.-criv) vuill. infection

Abstract

To look into the possibilities of dual tolerance for both abiotic and biotic stresses in silkworms, thermotolerant bivoltine silkworm breeds were infected with Beauveria bassiana and their growth response was studied. Ten thermotolerant bivoltine silkworm breeds of which eight breeds viz., B1, B2, B3, B4, B5, B6, B7 and B8 from CSRTI, Mysore and two breeds viz., APS12 and APS45from APSSRDI, Hindupur along with CSR2 as control were inoculated with Beauveria bassiana spores. The B4 breed showed highest LC50value (68,625.71 spores / ml) indicating to be more tolerant to fungal infection than others. The quantitative traits in B4 thermotolerant bivoltine silkworm breed under both muscardine inoculation and high temperature treatment revealed significantly highest ERR, fifth instar larval weight, cocoon yield by number, cocoon yield by weight, single cocoon weight, shell weight, filament length and filament weight. However, shell ratio was higher in B4 under muscardine infection but in B3 under high temperature treatment. Thepupal weight showed non-significant difference in all the breeds under muscardine infection but showed significant difference under high temperature treatment. The Correlation between the performance of the breeds under thermal treatment and muscardine infection revealed significant positive correlation with respect to fifth instar larval weight (0.80), shell weight (0.58), filament length (0.79) and filament weight (0.83). Under both muscardine infection and high temperature treatment the regression analysis revealed that the cocoon yield by number per 1000 worms (2.35 and 3.02, respectively) and single cocoon weight (1823.32 and 4771.60, respectively) had a positive contribution to cocoon yield under both the conditions.