Investigations on exploitation of heterosis in cotton (Gossypium hirsutum L.) using male sterility

Study of cytoplasmic-genic and genetic male sterility (CMS and GMS) for exploitation of heterosis in cotton led to the identification of five suitable exotic Gossypium hirsutum, restorers of cytoplasmic-genic male sterility. The 29 CMS hybrids obtained by using 6 male sterile lines (A lines) and 5 restorer lines (R lines), as well as 172 GMS hybrids involving 9 genetic male sterile lines were compared with Several cotton genotypes for their seed cotton yield and eronomic characters. The GMS hybrids were superior to CMS hybrids, significantly surpassing the yield of the commercial Hybrid-4. The CMS hybrids did not show significant improvement in yield over the commercial cotton hybrid. The genetic background, local adaptability, and diversity of parents appeared to be responsible for the superiority of GMS hybrids over CMS hybrids. The presence of strong sterile cytoplasm may also be a probable reason for the poor performance of CMS hybrids, besides the limited number of hybrids based on cytoplasmic-genic male sterility system in contrast with genetic male sterility system, where large number of hybrid combinations were possible and thus produced and tested. The study also revealed that 4 out 01 172 GMS hybrids with high economic heterosis for yield and also superior to Hybrid 4 in four other economic characters can be commercially exploited. Since the female parents of these hybrids are male sterile, the cost of hybrid seed production can be substantially redured.