Genetic Identification and Origin of Grapevine Cultivars (Vitis vinifera L.) in Tunisia

Abstract

Nine nuclear microsatellite (SSR) markers were used to characterize 35 wild grapevines (Vitis vinifera subsp. sylvestris) prospected from northwestern Tunisia and 64 cultivated accessions (Vitis vinifera subsp. vinifera) maintained in the repository of the Arid Land Institute of Medenine (Tunisia). All analyzed SSR loci were polymorphic, revealing 62 distinct genotypes, including 31 cultivated and 31 wild accessions. Some cases of synonymies, color sports, and homonymies were detected as well as matches with previously analyzed Tunisian samples and international cultivars. Chloroplast microsatellite analyses showed that chlorotype A was most abundant in wild samples (65%), whereas chlorotypes C and D were more frequent in cultivated genotypes (45% and 23% respectively). Genotypic analysis showed that both Tunisian wild and cultivated samples maintain high levels of genetic variation and high average posterior probabilities of assignment to their group of origin. This is in agreement with the estimated low gene flow between cultivated and wild forms, revealing that most cultivated accessions do not derive directly from the local wild populations but could correspond to materials introduced from different locations or derived from spontaneous hybridizations among them. However, we could not discard the hypothesis that a few analyzed samples could arise from hybridization events between wild and cultivated grapevines.