Identification of fertility restorers for Gossypium harknessii based cytoplasmic male sterility system in cotton (Gossypium hirsutum L.)

Abstract

Cytoplasmic male sterility (CMS) is a maternally inherited trait conferring the inability to produce functional pollen because of interaction between cytoplasm and nuclear genes. Since CMS does not affect female fertility, male sterile plants are able to set seeds as long as viable pollens are provided. The presence of certain nuclear genes, Rf (restoring 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 for many crops [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 L.) as a male parent to a wild species G. harknessii [2]. This system is involving cytoplasmic male sterility (A), maintainer (B) and restorer (R) line, has been widely used to develop hybrid rice varieties [3, 4]. 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 [5,6]. 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. [7]. Whereas in case of genetic male sterility system the abnormality is post meiotic. Therefore, the scope of CGMS system will be greater if more number of divergent restorer lines are identified. It was thought worthwhile to evaluate these CGMS lines for their potentiality as parents for hybrids and also to identify suitable restorers from the G. hirsutum accessions available in the gene bank.