CYTOLOGICAL EXPRESSION IN THE MALE-STERILE MS MUTANT IN WATERMELON

We described a spontaneous male-sterile mutant inherited as a single r ecessive nuclear gene (ms) in watermelon. The male sterility was expre ssed in androecium development, disrupting male-flower function. Femal e fertility of the male-sterile phenotype was normal. Comparative hist ological analysis between sterile (msms) and fertile (MsMs, Msms) geno types showed that the lack of tapetum and the abnormal deposition of f luorescing proteins precluded meiocyte development after telophase II and caused degeneration of meiocytes in sterile anthers. The ms mutati on altered the pattern of differentiation of anther wall and resulted in the persistence of five to seven cell layers of locule wall through out meiosis. The consistent inhibition of ontogeny of meiocytes at tel ophase II, the absence of pollen production under the varying environm ental conditions, and the normal female fertility of the male-sterile genotype permit exploitation of this mutation in hybrid seed productio n.