Heterosis and Combining Ability for Earliness and Its Related Traits in Cotton (gossypium Hirsutum L.)

Cotton is one of the most important commercial crops in India, playing a key role in national economy. Short duration and high yielding varieties are always required for better quality and lint production. Early maturing crops avoid disease and pest epidemics due to which plant breeders have positioned adequate pressure on the development of early maturing crop plants (Singh, 2004). Term earliness is particular to crop production that refers to harvest the crop as early as possible without incurring significant yield losses. Average vegetative growth period of cotton throughout the world is found to be 135-150 days (Kassianenko, 2003). India is pioneer in commercialization of heterosis in cotton. A noticeable heterosis is reported in cotton by many workers (Khadi et al., 1993). Even though heterosis occurs in cotton, it has not been utilized widely as compared to maize and castor due to difficulties in producing cheap commercial F1 hybrid seed production. For better exploitation of heterosis in cotton, development of simple and economically viable hybrid seed production technique is essential. Commercial exploitation of heterosis is possible only when it is high and consistent across the diversified environments for large scale hybrid seed production. Exploiting heterosis is one of the methods used to increase cotton yields that have stagnated in recent years. The important reasons attributed for this is the lack of systematic efforts made to develop hybrid oriented populations, derived lines with improved combining ability and develop new hybrids based on such genetically diverse high combiner lines (Choudhary et al., 2014).