Screening and Identification of Thermo-Tolerant Silkworm (Bombyx mori L.) Breeds for Sustainable Sericulture Under Thermal Stress Using the Evaluation Index Method

Abstract

Thermal stress is one of the major environmental constraints affecting silkworm productivity and silk quality, particularly under tropical and sub-tropical conditions. The present study was conducted at SKUAST-Jammu in the year 2022 using Completely Randomized Design (CRD) with three replications. The study aimed to evaluate thermotolerance in different silkworm breeds using the Evaluation Index (EI) method to identify heat-resilient genotypes suitable for high temperature rearing conditions. The breeds were reared under ambient and elevated temperature regimes, and key economic and physiological traits such as fecundity, pupation rate, cocoon yield, cocoon weight, shell weight, shell ratio, filament denier and filament length were recorded. The collected data were statistically analyzed, and the overall performance of each breed was assessed through the Evaluation Index method, which integrates multiple traits into a single composite score to enable comparative ranking. Breeds exhibiting higher EI values under high temperature conditions were considered thermo-tolerant and stable in performance. The results revealed significant variation among breeds in their response to thermal stress. Certain breeds like ND5, U-4, U-6 and U-3 maintained higher pupation rate, cocoon traits, and filament quality under elevated temperature, resulting in superior EI scores. The identified heat-tolerant breeds may be utilized in breeding programs and commercial rearing to sustain silk production under changing climatic conditions.