INHERITANCE AND MOLECULAR MAPPING OF ANDROMONOECIOUS AND GYNOECIOUS SEX DETERMINING GENES IN MELON (CUCUMIS MELO L.)

The inheritance of sex determination genes in melon was studied using the populations of F 1 , F 2 , BC 1 P 1 and BC 1 P 2 derived from two parental lines, the gynoecious WI998 and andromonoecious TopMark. These populations were segregating at two loci for sex determination: the a gene locus for andromonoecious and the m gene locus for gynoecious sex expression. It was found that different phenotypes corresponded to different genotypes in sex expression: A_G_ = monoecious; A_gg = gynomonecious; aaG_ = andromonoecious; aagg = hemaphrodite; and A_ggmm = gynoecious. A preliminary genetic mapping of these two gene loci were conducted with microsatellite markers in the F 2 population with 298 individuals. Fifty-five polymorphic SSR markers were identified and applied for linkage analysis to construct the genetic map which spanned 666.7 cM with a mean marker interval of 17.09 cM. SSR marker MU5549-1 linked to gene a with the distance at 13.5 cM and SSR marker MU14723-2 linked to gene m with the distance at 11.6 cM.