Development and characterization of fertility restorers in cytoplasmic genetic male sterile lines of cotton (Gossypium hirsutum L.) derived from Gossypium harknessii

Abstract

Cytoplasmic-nuclear male sterility (CGMS) is a maternally inherited trait and in conjunction with nuclear genome suppresses the production of viable pollen grains without 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 (restoring fertility) can effectively suppress the malesterile cytoplasm and restore pollen fertility. However, 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 [1]. This system is involving cytoplasmic male sterility (A), maintainer (B) and restorer (R) lines, has been widely used to develop hybrid rice varieties [2, 3]. 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 [4, 5]. The CMS system could not be exploited commercially because of complex nature of fertility restoration and a suspected penalty on seed cotton yield and yield contributing traits as reported by several workers [6-9]. The reduction in yield and its component traits may be due to the less compatibility of alien cytoplasm with the nuclear genes of G. hirsutum. But by the course of evolution this incompatibility can be overcome. By keeping this in view, breeding programme to develop alloplasmic restorer lines using pedigree method was initiated.