Cytohistological studies on male sterility in different cytoplasmic genetic male sterile lines of rice (Oryza sativa L.)

Cytological, cytohistological and morphological causes for pollen breakdown in two cytoplasmic genetic male sterile lines MS 577A and IR 58025A were carried out in comparison with their corresponding maintainer lines (MS 5778 and IR 580258) and a restorer line (Vajram). The anther sac layers, i.e. the inner tapetum, middle endothecium and outer epidermis showed slight variation in their thickness at all stages among the lines but showed normal behaviourin development in both the cytoplasmic genetic male sterile lines, IR 58025A and MS 577A, as well as their maintainer lines (IR 580258 and MS 5778) and the restorer (Vajram). In IR 58025A, the critical stage of breakdown was observed to be at binucleate stage whereas in MS 577A pollen grains were morphologically similar to its maintainer line but failed to fertile in selfing. The reason for pollen breakdown may be incompatibility between nuclear and plasma genes.