Four pure mulberry silkworm breeds viz., Pure Mysore, Nistari, NB4D2 & CSR2 and two hybrid (Pure Mysore x CSR2 and Nistari x NB4D2 ) silkworms were selected for the present study. The specific activity of esterase in the haemolymph, midgut and fat body tissues was estimated. The qualitative analysis of esterase was carried out by Native-PAGE. The commercial characters viz., fecundity, larval weight, larval duration, cocoon weight, shell weight, shell ratio, filament length, denier and renditta were selected. The esterase activity levels were subjected for regression analysis against selected commercial characters to know the level and kind of correlation between them. The results of statistical analysis clearly showed that the haemolymph esterase activity levels exhibited positive correlation with denier, filament length, larval duration, shell ratio, cocoon weight and shell weight. The midgut esterase activity levels showed positive correlation with denier, fecundity, filament length, larval weight, shell ratio, cocoon weight and shell weight. Also, the activity levels of fat body esterase indicated positive correlation with denier, fecundity, filament length, larval weight, shell ratio, cocoon weight and shell weight only. The zymograms of esterase also exhibited variation among the selected silkworm breeds.
