Development and Characterization of a Molecular Marker Associated with Female Flowers in Muscadine Grape (Vitis rotundifolia)

Muscadines have three flower types: hermaphroditic, male, and female. Male flowers have only filaments and anthers. In contrast, both female and hermaphroditic flowers are morphologically perfect, but female flowers have reflexed stamens (as opposed to upright) and non-functional pollen. At present, flower sex in muscadine is thought to be controlled by a single major locus with three alleles: M (male), H (hermaphrodite), and F (female) in the dominance relationship M > H > F, although this theory does not explain the existence of M progeny in some H × H crosses. Primers derived from previously identified candidate genes located at the sex locus of V. viniferawere used to generate amplicons from muscadine genotypes with differing flower types. Sequence analysis of the amplicons revealed an In/Del polymorphism in a trehalose-6-phosphate phosphatase (TPP) gene among genotypes. Primers were designed flanking the In/Del to examine the polymorphism in muscadine M, H, and F genotypes and in F×H, F×M, and H×H segregating populations. A co-dominant marker was developed that is able to differentiate the F allele from the M and H alleles. The marker is able to accurately predict the presence of female flowers. The use of the marker in muscadine breeding programs will be discussed.