Genetic isolation and diffusion of wild grapevine Italian and Spanish populations as estimated by nuclear and chloroplast SSR analysis.

Genetic relationship among six Italian and four Spanish populations of wild grapevine (Vitis vinifera ssp. silvestris) has been investigated by using nuclear and chloroplast SSR analysis. Results show that the Italian populations are characterised by the high genomic diversity within and among populations, with a peak of heterozygosity (Ho = 0.7537) for a population collected in Southern Italy. The demonstration of high gene flow among the Italian populations suggests a central role for the Italian peninsula as a principal refugial area of wild grapevines during the last glaciation. On the other hand, the high level of genetic distance detected among the Spanish population combined with the detection of low gene flow show that these populations suffered a severe bottleneck during their history. The FST values calculated in the case of an Italian population sampled in the Sardinia island showed that genes of these plants exchanged equally with the Italian and the Spanish populations. This points to Sardinia as a crossing area between Italy and Spain during grapevine postglacial recolonization. By providing information on population history, genetic structure and gene flow, and by identifying areas harbouring high levels of wild grape variability, this study provides the bases for the preservation of biodiversity of wild grapevine.