ABSTRACT
KEY MESSAGE: The maternal and paternal parentage of 36 rootstocks was determined and verified. The results of this study indicate that existing grape rootstocks are closely related to each other and have a narrow genetic background. Rootstocks are used to protect grapevines from biotic and abiotic stresses including phylloxera, nematodes, viruses, limestone-based soils, salinity and drought. The most important rootstocks were developed from three grape species between the 1890s and the 1930s in European breeding programs. In this report, we developed nuclear and chloroplast SSR fingerprint data from rootstock selections maintained in germplasm collections, compared them to develop a reference dataset, and carried out parentage analysis to resolve previously reported, and determine new, breeding records. We refined and updated the parentage of 26 rootstocks based on 21 nuclear and 14 chloroplast markers. Results indicate that 39% of the genetic background of analyzed rootstocks originated from only three accessions of three grape species: Vitis berlandieri cv. Rességuier 2, V. rupestris cv. du Lot and V. riparia cv. Gloire de Montpellier. Results determined that Rességuier 2 is the maternal parent for 14 commercial rootstocks, 9 of which are full-sibs with Gloire de Montpellier as the paternal parent. Similarly, du Lot is the paternal parent of nine rootstocks. The pedigree information for 28 rootstocks was determined or corrected in this study. The previously reported pedigree information for eight of the rootstocks was correct. The results found that the world's existing rootstocks have a narrow genetic base derived from only a few American grape species. Future rootstock breeding efforts should use a more diverse array of species to combat a changing climate and pest pressure.
Subject(s)
Genetic Variation , Plant Breeding , Plant Roots/genetics , Vitis/genetics , Genotype , Plant Roots/growth & development , Vitis/growth & developmentABSTRACT
BACKGROUND: The mountainous region between the Caucasus and China is considered to be the center of domestication for grapevine. Despite the importance of Central Asia in the history of grape growing, information about the extent and distribution of grape genetic variation in this region is limited in comparison to wild and cultivated grapevines from around the Mediterranean basin. The principal goal of this work was to survey the genetic diversity and relationships among wild and cultivated grape germplasm from the Caucasus, Central Asia, and the Mediterranean basin collectively to understand gene flow, possible domestication events and adaptive introgression. RESULTS: A total of 1378 wild and cultivated grapevines collected around the Mediterranean basin and from Central Asia were tested with a set of 20 nuclear SSR markers. Genetic data were analyzed (Cluster analysis, Principal Coordinate Analysis and STRUCTURE) to identify groups, and the results were validated by Nei's genetic distance, pairwise FST analysis and assignment tests. All of these analyses identified three genetic groups: G1, wild accessions from Croatia, France, Italy and Spain; G2, wild accessions from Armenia, Azerbaijan and Georgia; and G3, cultivars from Spain, France, Italy, Georgia, Iran, Pakistan and Turkmenistan, which included a small group of wild accessions from Georgia and Croatia. Wild accessions from Georgia clustered with cultivated grape from the same area (proles pontica), but also with Western Europe (proles occidentalis), supporting Georgia as the ancient center of grapevine domestication. In addition, cluster analysis indicated that Western European wild grapes grouped with cultivated grapes from the same area, suggesting that the cultivated proles occidentalis contributed more to the early development of wine grapes than the wild vines from Eastern Europe. CONCLUSIONS: The analysis of genetic relationships among the tested genotypes provided evidence of genetic relationships between wild and cultivated accessions in the Mediterranean basin and Central Asia. The genetic structure indicated a considerable amount of gene flow, which limited the differentiation between the two subspecies. The results also indicated that grapes with mixed ancestry occur in the regions where wild grapevines were domesticated.
