Cytoplasmic male sterility in sorghum: Organization and expression of mitochondrial genes in Indian CMS cytoplasms

Cytoplasmic male sterility in sorghum has been reported in a number of varieties originating in different geographical regions (India, Africa and America). We have attempted to characterize three male sterile cytoplasms of Indian origin designated as Maldandi, Guntur and Vizianagaram by studying restriction fragment length polymorphisms (RFLPs) and expression patterns of 14 mitochondrial genes. Our results indicate that the cytoplasms, classified tentatively as Indian A₄ types, are distinct from the American A₄ and A₁ types. Although they are identical to each other with respect to the location of 10 of the mitochondrial genes selected, they can be distinguished from each other on the basis of RFLPs inatp6, atp9 andrrn18. Further the three cytoplasms differ from their maintainers in the location ofnad3, rpsl2 andatpA. Differences are also observed in the pattern of expression ofatpA between all the sterile lines and their respective maintainers.