Genetic structure of endangered wild grapevine Vitis vinifera ssp sylvestris populations from Tunisia: Implications for conservation and management

Wild grapes, considered as the putative ancestor of the cultivated form, represent the only endemic taxon of the Vitaceae in Europe and the Maghreb. The species has become highly threatened because of habitat loss and intensive forest exploitation. In this work, we analyzed genetic aspects that could shed light on the evolution and conservation of wild grapes that still be found in forests along river banks in Tunisia. We examined the genetic structure of twenty populations using 10 nuclear SSR loci. Vitis sylvestris has a high level of genetic variation with 84.5% of the loci assayed being polymorphic, a mean number of alleles of 10.4, and a mean heterozygosity per population of 0.7546. We calculated Wright's FST statistic to estimate gene flow indirectly and to evaluate whether or not there was genetic structuring among populations. We found a marked differentiation among populations according to FST values and clustering. AMOVA has shown that most of the variation was partitioned between rather than among populations. A significant pattern of isolation by distance was found which implies that each population would constitute a distinct pool of genetic variation that warrants conservation. Finally, the exponential curve of the relationship between genetic distances and demographic data strongly suggests that due to populations' small sizes and fragmentation, V. sylyestris is actually at high risk of extinction in Tunisia. Therefore, all studied populations are valuable for conservation. (C) 2013 Elsevier B.V. All rights reserved.