Georgian wild grapevine germplasm: A genetic and phenotypic characterization

Abstract

The wild progenitor of the cultivated grapevine, Vitis vinifera subsp. sylvestris, represents a crucial reservoir of genetic diversity and adaptive traits of significant value for conservation and breeding programs. Georgia, recognized as one of the primary centers of grapevine domestication, still harbors remnant populations of wild grapevines that preserve unique and ancient genetic lineages. In this study, the genetic diversity and population structure of 23 wild Georgian grapevine accessions were investigated using 18k SNP loci and compared with 112 additional wild genotypes from across the Mediterranean Basin. Genetic analyses revealed that wild grapevine populationsfrom Eastern Georgia form a single, highly diverse genetic pool with limited overall stratification. However, cluster analyses detected geographically associated substructures, particularly within the Kakheti region. Within the broader Mediterranean context, Georgian wild grapevines displayed marked genetic distinctiveness. Both clustering approaches and PCAconsistently identified the Georgian samplesas a coherent and genetically differentiated group, with minimal overlap with Mediterranean accessions.

Population structure analyses supported the presence of three ancestral populations: the Georgian group formed an independent cluster (POP2), while North African and Iberian Peninsula samples grouped together (POP1), and Western– Central European genotypesconstituted a third cluster (POP3). Aminimum spanning network further highlighted the presence of three main populations, with the North African group acting as a genetic bridge between Georgian and Western–Central European wild grapevines. TreeMix analysis indicated aclear tree-like divergence pattern among the three populations, with POP1 and POP2 forming sister groups and POP3 diverging earlier. Georgian samples exhibited the highest level of genetic drift, and no evidence of admixture or post-divergence gene flow was detected. In addition to genomic analyses, a phenotypic characterization of the Georgian wild grapevine germplasm was carried out in order to assessmorphological variability and adaptive traits. Forty one accessions, included also those 21 genotyped, available in the collection anddescribed by 52 OIV ampelographic descriptors, demonstrated presence of 8 homogenous descriptors and 44 heterogeneous ones. Thisdescriptors, selected by the COST FA1003 project and covering all organs of grapevine, together with photos became the basis for producing of the detailed ampelographic cards. Altogether, these results underline the genetic uniqueness of Georgian wild grapevinepopulations and emphasize the importance of preserving this germplasm as a valuable resource for future conservation strategies andgrapevine breeding programs.

Acknowledgements

The work was supported in the framework of the “Research Project for the Study of Georgian Grapes and Wine Culture” of the National Wine Agency of Georgia.