ARS | Publication request: Genetic structure, differentiation, and phylogeny of the genus Vitis: implications for genetic conservation

Submitted to: Acta Horticulture Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 19, 2007
Publication Date: N/A
Repository URL: http://www.actahort.org/

Interpretive Summary: The genus Vitis is typically divided into two subgenera, Vitis (2n=6x=38) comprising almost all of the total of about 70 taxa described in the genus except for two taxa, V. rotundifolia and V. popenoei representing the subgenus Muscadinia (2n=6x=40). About two-thirds of Vitis are native to North America and one-third distributed across Europe and Central and West Asia. Much of the taxonomic knowledge of Vitis comes from studies based on morphological criterion and riddled with difficulties in establishing genetic identities of different taxa. This confusion is due to widespread introgression among sympatric taxa resulting in clinal variation masking the taxonomic and ecological boundaries. Three hundred sixty grape accessions representing 44 taxa with both the Old and New World distributions including the cultivated V. vinifera and its putative progenitor, V. v. ssp. sylvestris, three taxa of Muscadini, and some accessions from related genera were analyzed for genetic structure and differentiation using 16 polymorphic microsatellite loci. We address the transportability and utility of these markers across the cultivated species and their wild relatives in the characterization of gene pools for efficient conservation, management, and utilization of genetic resources of Vitis. Examination of phylogenetic patterns within the genus Vitis revealed many affinities more or less matching the taxonomic series established based on morphological criterion. Chinese species exhibited significant genetic differentiation with as many as three major affinities and some of them showing strong relationships with many American taxa/series. The marginal heterozygote deficiency observed for some of the loci suggests population substructuring within and between taxa. However, there was significant differentiation between taxa as compared to between series. Overall, the interplay of local differentiation and introgression has played a significant role in shaping the genetic structure in Vitis. We further discuss the implications of the complex multidimensional nature of microsatellite variability in the genus for the development of conservation and management strategies.

Technical Abstract: Examination of phylogenetic patterns within Vitis using 18 microsatellite markers and AFLPs revealed many affinities differing somewhat from the traditional taxonomic classifications based on morphological criteria. East Asian taxa from China exhibited significant divergence from the North American group, however, some aligned with American taxa/series. Partitioning of molecular variation suggested significant amount of total variation (~74%) is accounted for by ferences among genotypes within taxa as compared to among taxa within series (~17%) and among series within the genus Vitis (~9%). Although significant gene flow was evident at all levels of classification there was reasonable differentiation among taxa and series. The results suggest that Vitis represents a complex gene pool within which the interplay of local selection, introgression, drift, and reticulate evolution has played a significant role in shaping the genetic structure and phylogeny of Vitis.