Genetics of fertility restoration for the A1 cytoplasmic genic male sterility system in pearl millet (Pennisetum glaucum (L.) R. Br.)

With the objective to investigate the inheritance pattern of fertility restoration of A1cytoplasm in multi-environments, six crosses were developed by crossing two A1 cytoplasm-based male sterile lines (A-lines) with three diverse restorers (R-lines). The parents, 6 F2s and 6 BC1s were evaluated in the rainy season at Delhi and summer season at Delhi and Dharwad. Four crosses viz.,576A1×PPMI 1012, 411A1× PPMI 1012, 576A1× ICMR 06111 and 411A1× ICMR 06111 showed a segregation ratio of fertile: semi-fertile: sterile as 9:3:4 and 1:1:2 in F2 and BC1 generations, respectively, based on pollen fertility and seed set percent data, indicating digenic supplementary gene action. In the other two crosses, i.e., 576A1× HTP 94/54 and 411A1× HTP 94/54, different digenic ratios of 9:7 and 1:3 of fertile and sterile plants were observed in F2 and BC1 generations, respectively, indicating complementary interaction of two genes. The deviation of expected ratios in the summer season at Delhi resulted due to excess sterile plants, as influenced by modifiers and environmental conditions that prevailed during the dry season. Thus, in the present investigation, fertility restoration of A1-based CGMS system was observed to be governed by two major genes. Still, with different types of epistatic interactions, digenic inheritance of A1 cytoplasm suggests that test of allelism and genetic mapping of fertility restorer genes can be taken up in the future.