GENETIC CONTROL OF TENDRIL DISTRIBUTION IN A GRAPEVINE ROOTSTOCK HYBRID POPULATION

Grapevine tendril distribution is a characteristic of varieties and species. We examined the tendril distribution on a population of seedlings from a 161-49C x (V. labrusca x V. mustangensis) hybridization. 16149C is a V. riparia x V. berlandieri hybrid that ordinarily bears tendrils in a discontinuous pattern. Although the V. labrusca x V. mustangensis parent frequently demonstrates more than two tendrils in sequence, it does show nodes without tendrils and as such cannot be described as strictly continuous in its tendril distribution. Grapevine tendrils and clusters (inflorescences) are found at the node opposite a leaf. Cultivars and spe cies exhibit some variation in tendril distribution, the phyllotactic patterning of which nodes have tendrils (or clusters) and which do not. Most Vitis species and cultivars have two nodes with tendrils followed by a node without a tendril (Mullins et al., 1992; Gerrath et al., 1998). This pattern is called intermittent tendril distribution. However, in the North American species V. labrusca and some V. labrusca interspecific hy brids, a tendril is found at every node (continuous tendril distribution). Some interspecific hybrid cultivars have an intermediate tendril distribution, with more than two nodes in a row bearing tendrils, but with occasional tendril-free nodes. Cousins et al. (2005) reported exploratory studies in the genetic control of phyllotactic patterning. Here we report in-depth analysis of a population segregating for tendril distribution patterns.