Microsporogenesis and the Mechanism of Cytoplasmic Male Sterility in Maize

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Abstract
Examination of the structural changes occurring during microsporogenesis in cms-T, -C and -S Zea mays L. with different nuclear backgrounds revealed considerable variations in the stages at which abortion of the sporocytes occurred within each cytoplasmic genotype. This variation was not associated with the nuclear background. Significantly, we found that the mitochondria in cms-T plants did not always follow the pattern of degeneration described previously. We conclude that these observations are not consistent with a proposed mechanism of cytoplasmic male sterility involving the direct, antagonistic action of an anther produced substance on an altered mitochondrion or plastid, that is functionally normal in the rest of the plant. The value of microscopic studies in detecting variation in apparently uniform material is emphasised, though it is recognized that other methods will be required to elucidate the mechanism of male sterility.