Genetic study of wild grapevines in La Rioja región

Abstract

Since the mid-1980s, several surveys have been carried out in La Rioja to search for populations of the sylvestrisgrapevine subspecies (Vitis vinifera L. subsp. sylvestris Gmelin). The banks of the Ebro River and its tributaries (Alhama, Cidacos, Leza, Iregua, Najerilla, Oja and Tirón rivers), as well as the surrounding vegetation of their valleys have been covered. So far, all the populations found are alluvial, forming part of the riparian vegetation of the Najerilla (the first reported population in La Rioja [1]), Iregua, and the vicinity of Oja valleys. Nevertheless, doubts arose from the beginning about the `sylvestris purity¿ of some of these wild vines. In this work, leaves and/or cuttings from 83 vines have been used for genetic analyses: 63 vines were sampled in the wild in La Rioja region (17 from Najerilla banks, 43 from Iregua banks, and 3 from Agualinos stream, tributary of the Oja river), and 20 vines were sampled in the grapevine sylvestris collection of the University of La Rioja, originally collected as wild vines from the Najerilla valley. DNAs were extracted and genotyped at 6 microsatellite and 240 SNP markers. A total of 58 different genotypes were found, 20 in the Najerilla population, 36 in the Iregua population and 2 in the Oja population. These genotypes were included in a large genetic structure analysis of more than 2.800 genotypes representing worldwide sylvestrisand sativa subspecies. More than 84% of the wild samples from La Rioja showed a high membership coefficient to the sylvestris population, supporting their sylvestris condition. A local analysis focused on genotypes of cultivated and wild vines found in La Rioja separated them into two main clusters, with a clear division between sylvestris and cultivated vines. Some wild vine genotypes were found in intermediate positions between these two groups, indicating the existence of an introgression of the sativa gene pool into the sylvestris population, constituting an additional threat to the sylvestris subspecies.