Inheritance of male-fertility restoration in A1, A2, A3 and A4(M) cytoplasmic male-sterility systems of sorghum [Sorghum bicolor (L.) Moench]

Abstract

Almost all the sorghum [Sorghum bicolor (L.) Moench] hybrids commercially exploited to date are based on A1 CMS (cytoplasmic-nuclear male-sterility) system. For genetic diversification and to produce more heterotic hybrids, all the available CMS systems are to be studied for genetics of male-fertility restoration preferably in isonuclear backgrounds. The A1, A2, A3 and A4(M) cytoplasms present in three different nuclear backgrounds were crossed with two common restorers. The segregation of fertile and sterile plants observed in F2 and BC1 populations during rainy and post-rainy seasons of 2007 was tested with c2 for goodness of fit for monogenic, digenic and trigenic ratios. The fertility restoration of A1 CMS system was governed by one basic gene and two duplicate complimentary genes (45F:19S in F2) all acting in dominant fashion while the fertility restoration of A2 and A3 CMS systems was governed by three genes where all of the three complimentary genes in dominant condition restore fertility (27F:37S in F2). The fertility restoration in A4(M) CMS system was governed by three genes where any two of the three dominant duplicate-complimentary genes restored fertility (54F:10S in F2) in post-rainy season while two complementary genes in dominant state restored fertility (9F:7S in F2) in rainy season in the absence of expression of the third gene.