Identification and characterization of new fertility restorers in cytoplasmic genetic male sterility (CGMS) of cotton [Gossypium hirsutum (L.)] derived from Gossypium harknessii

Abstract

Cytoplasmic-nuclear male sterility (CGMS) is a maternally inherited trait, in conjuction with nuclear genome, suppresses the production of viable pollen grains, while not affecting the female fertility. Male sterile plants are able to set seeds as long as viable pollens are provided. The presence of certain nuclear genes, Rf (reetoring fertility), can effectively suppress the male-sterile cytoplasm and restore pollen fertility. The application of CMS/Rf system has proved to be an effective means to produce commercial F1 hybrid seed in a wide range of more than 150 plant species. Most CMS types have occurred naturally or in interspecific crosses [1]. The success in development of cotton hybrid largely depends on availability of the effective restorer and precise basic knowledge on the genetics of fertility restoration of such lines. The first F1 line of commercial cotton was introduced by crossing an upland cotton (G, hirsutum) as a male parent to a wild species G. harknessii [2]. Therefore cytoplasmic male sterility (A), maintainer (B) and restorer (R) line, system can be used to develop hybrid cotton varieties, Reduction in cost of hybrid seed production is possible by using male sterility, The best-known sterile cytoplasmic source available for heterosis breeding in cotton is from G. harknessii developed by Meyer [3]. Gossypium harknessii Brandagee (02-2) which is a diploid (2n = 26) was used as female by Meyer [4] to transfer G, hirsutum genome in the cytoplasm of G. harknessii. The resultant triploid was made hexaploid (2n = 78) using colchicine. Male sterile tetraploid plants were recovered from cross between hexaploid and tetraploids. The use of this CGMS source is limited for want of potential restorers. In case of cytoplasmic male sterility system the abnormality of disintegration before pollen mother cell undergo meiosis has been reported by Khadi et al. [5],