Molecular characterization of sterility cytoplasm and tagging of fertility restorer genes Rf in sorghum

Abstract

Sorghum (Sorghum bicolor (L.) Moench) is one of the important cereal crops widely cultivated for food, fodder, feed and fuel. In sorghum, Cytoplasmic Male Sterility (CMS) is effectively used to exploit the phenomenon of heterosis for increased grain yield, resistance to pests, higher biomass, etc. CMS discovery followed by the development of fertility restorer (R) lines (with ability to restore male fertility) allowed the mass production of F1 hybrid seed in sorghum. So far, 30 sorghum hybrids at national and more than 40 hybrids at state level have been released in India for commercial cultivation both by private and public sectors. The commercial hybrids predominantly cultivated all over the globe are based on A1 (milo) cytoplasm, with infrequent exploitation of A2 hybrids. Cytoplasmic homogeneity restricts the nuclear genetic diversity of male-sterile (A) and restorer (R) lines in hybrid development and is pre disposes to devastation of the crop. In order to avoid devastating consequences, as happened in maize (Helminthosporum leaf blight susceptibility linked to maize T-cytoplasm) (Tatum, 1971), and to broaden genetic and cytoplasmic base of hybrids, there is a need for employing alternate CMS systems and their restorers with high heterotic potential for hybrid development. Exploiting alternate cytoplasms in commercial F1 hybrids adds cytoplasmic and nuclear genetic diversity to hybrid breeding in sorghum, and helps to evade the risks associated with the use of single cytoplasm and narrow genetic base restorers. newline