Abstract
BackgroundThe mountainous region between the Caucasus and China is considered to be the center of domestication for grapevine. Despite the importance of Central Asia in the history of grape growing, information about the extent and distribution of grape genetic variation in this region is limited in comparison to wild and cultivated grapevines from around the Mediterranean basin. The principal goal of this work was to survey the genetic diversity and relationships among wild and cultivated grape germplasm from the Caucasus, Central Asia, and the Mediterranean basin collectively to understand gene flow, possible domestication events and adaptive introgression.ResultsA total of 1378 wild and cultivated grapevines collected around the Mediterranean basin and from Central Asia were tested with a set of 20 nuclear SSR markers. Genetic data were analyzed (Cluster analysis, Principal Coordinate Analysis and STRUCTURE) to identify groups, and the results were validated by Nei’s genetic distance, pairwise FST analysis and assignment tests. All of these analyses identified three genetic groups: G1, wild accessions from Croatia, France, Italy and Spain; G2, wild accessions from Armenia, Azerbaijan and Georgia; and G3, cultivars from Spain, France, Italy, Georgia, Iran, Pakistan and Turkmenistan, which included a small group of wild accessions from Georgia and Croatia. Wild accessions from Georgia clustered with cultivated grape from the same area (proles pontica), but also with Western Europe (proles occidentalis), supporting Georgia as the ancient center of grapevine domestication. In addition, cluster analysis indicated that Western European wild grapes grouped with cultivated grapes from the same area, suggesting that the cultivated proles occidentalis contributed more to the early development of wine grapes than the wild vines from Eastern Europe.ConclusionsThe analysis of genetic relationships among the tested genotypes provided evidence of genetic relationships between wild and cultivated accessions in the Mediterranean basin and Central Asia. The genetic structure indicated a considerable amount of gene flow, which limited the differentiation between the two subspecies. The results also indicated that grapes with mixed ancestry occur in the regions where wild grapevines were domesticated.
Highlights
The mountainous region between the Caucasus and China is considered to be the center of domestication for grapevine
The flower phenotype of the subsp. sylvestris accessions collected from Armenia, Azerbaijan and Georgia (USDA repository) could not be determined because these plants were maintained in small containers
Flower phenotypes assessed by DNA-based flower sex markers and field phenotyping of the wild forms of all the accessions of V. vinifera subsp. sylvestris are presented in Additional file 2: Table S2
Summary
The mountainous region between the Caucasus and China is considered to be the center of domestication for grapevine. Vitis vinifera L., the commonly cultivated grapevine, is one of the most widely grown fruit plants in the world [1]. It has subspecies with West Asiatic and European origins, and ranges from Central Asia to the Mediterranean Basin [2]. Within the genus Vitis, V. vinifera is the primary species used in the global wine industry, which occupied 7.5 million hectares in 2012 and produced more than 67 million tons of grapes (http://www.oiv.int/). Within this species, two subspecies have been described, V. vinifera subsp. The two subspecies form a genetic and taxonomic continuum without breeding barriers resulting in spontaneous hybrids where they occur sympatrically or paripatrically [6,7,8,9,10,11,12]
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