Evaluation of selected polyvoltine silkworm (Bombyx mori L.) genotypes under stress environmental condition in hotspots

Ten polyvoltine silkworm genotypes along with two control races viz., Pure mysore and Nistari have subjected to study for abiotic stress tolerance in the adverse climatic condition (high temperature and high humidity / high temperature and low humidity) under four selected hotspots to identify the phenotypically stable and stress tolerance genotypes for further utilization in the silkworm breeding programme. Eleven important economic traits including few raw silk parameters have been evaluated during the year 2005 to 2007. The data was subjected to analyze the phenotypic stability. The pooled ANOVA revealed that there is a significant variation among the test genotypes for 9 economic traits except pupation rate and shell ratio. The genotype-environment interaction coupled with environmental variation indicated significant variation for hatching %, matured larval weight, filament length and non-broken filament length. Based on the results, 4 genotypes viz., BMI-0045, BMI-0025, BMI-0027 and BMI0060 have been recommended for high temperature and low humidity zones preferably during summer months; and 4 genotypes viz., BMI-0027, BMI-0025, BMI-0040 and BMI-0016 have been recommended for high temperature and high humidity especially in north-east zones of Assam as they have showed better performance than both controls. It is also interesting to note that the genotypes BMI-0040 and BMI-0016 have showed regional specific performance for high temperature and high humidity; similarly, BMI-0060 has showed regional specificity for high temperature and low humidity. The above potential polyvoltine silkworm genotypes are recommended for use as a potential parents in the thermo-tolerance silkworm breeding programme.