UNRAVELING THE GENETICS OF FERTILITY RESTORATION IN DIVERSIFIED CYTOPLASMIC GENETIC MALE STERILE LINES (CGMS): INSIGHTS FROM HYBRID STUDIES IN PEARL MILLET [Pennisetum glaucum (L.) R. BR]

Cytoplasmic genetic male sterility is essential in pearl millet hybrid breeding, facilitating hybrid production by preventing pollen formation in male sterile lines and it requires fertility restorer lines to restore pollen production. This study examined nuclear-cytoplasmic interactions in diverse CGMS backgrounds (A1, A4, and A5) by developing 65 hybrids and evaluating their seed set percentage and pollen fertility under selfing conditions. Among the thirteen restorer lines seven lines namely, PT 6024, PT 6029, PT 6067, PT 6069, PT 6686, PT 6707, and PT 6715 consistently restored fertility in hybrids derived from both A1 and A4 male sterile lines. Conversely, PT 6059 exhibited zero seed set percentage and could potentially serve as a maintainer for all three cytoplasmic sources and highlights the significant impact of nuclear and cytoplasmic interactions on the fertility status. Along with this, pollen fertility of F1 was calculated for better results. Among the 65 hybrids, 34 were classified as fertile, 24 as sterile, and the rest as partial sterile based on interaction of CGMS system. Interestingly, hybrids based on A1 and A4 cytoplasmic lines showed restored male fertility, while those based on A5 were sterile. The regression between seed set and pollen fertility (R² = 0.24) effectively explained the observed data for categorization of fertility. The moderate significant correlation (>0.5) between pollen fertility and seed set percentage suggests that both the parameters can be used to categorize plants as fertile or sterile. Among the 65 newly developed hybrids, the hybrids CBMS 108A/1-1 x PT 6715 and CBMS 108A/1-1 x PT 6069 demonstrated significant positive heterosis for grain yield and its contributing traits. Hence, it showed potential for further evaluation in multilocational trials to confirm their superiority. Key words: Pearl millet, male sterility, fertility restoration, hybrids.