The introduction of hybrids and exploitation of heterosis had played a vital role in Indian sericulture industry, which clearly depicted a quantum jump in silk production during the last four decades. A systematic procedure to identify the best combiners by the breeders included combining ability test, line x tester analysis or D2 analysis for maximum expression of heterosis. The expression of heterosis expressed in crossbreed population was determined by the interaction between genotype and prevailing environmental factors. Except few exceptions, heterosis was found invariably higher in single crosses compared to three-way and double crosses. An attempt was made in this review article to elucidate briefly the concepts of heterosis, causes of heterosis, utilization of heterosis, manifestation of heterosis and its significance in silkworm breeding.
