Parentage Atlas of Italian Grapevine Varieties as Inferred From SNP Genotyping

Abstract

The Italian grape germplasm is characterized by a high level of richness in terms of varieties number, with nearly 600 wine grape varieties listed in the Italian National Register of Grapevine Varieties and with a plethora of autochthonous grapes. In the present study an extended SNP genotyping has been carried out on Italian germplasm of cultivated Vitis vinifera subsp. sativa and Vitis hybrids. Several hundred Italian varieties maintained in the repositories of scientific Institutions and about one thousand additional varieties derived from previous studies on European, Southern Italy, Magna Graecia and Georgian germplasm were considered. The large genotyping data obtained were used to check the presence of homonyms and synonyms, determine parental relationships, and identify the main ancestors of traditional Italian cultivars and closely-related accessions. The parentage among a set of 1,232 unique varieties has been assessed. A total of 92 new parent-offspring (PO) pairs and 14 new PO trios were identified. The resulted parentage network suggested that the traditional Italian grapevine germplasm originates largely from a few central varieties geographically distributed into several areas of genetic influence: "Strinto porcino" and its offspring "Sangiovese", "Mantonico bianco" and "Aglianico" mainly as founder varieties of South-Western Italy (IT-SW); Italian Adriatic Coast (IT-AC); and Central Italy with most varieties being offsprings of "Visparola", "Garganega" and "Bombino bianco"; "Termarina (Sciaccarello)" "Orsolina" and "Uva Tosca" as the main varieties of North-Western Italy (IT-NW) and Central Italy. The pedigree reconstruction by full-sib and second-degree relationships highlighted the key role of some cultivars, and, in particular, the centrality of "Visparola" in the origin of Italian germplasm appeared clear. An hypothetical migration of this variety within the Italian Peninsula from South to North along the eastern side, as well as of "Sangiovese" from South to Central Italy along the Western side might be supposed. Moreover, it was also highlighted that, among the main founders of muscat varieties, "Moscato bianco" and "Zibibbo (Muscat of Alexandria)" have spread over the whole Italy, with a high contribution by the former to germplasm of the North-Western of the peninsula.

Keywords: Italian founder varieties; Italian germplasm; Vitis vinifera; cultivar geographic areas; parent-offspring relationships; pedigree; second-degree relationships; single nucleotide polymorphism.

FIGURE 1

Network of main POs among Italian varieties organized according to their geographic areas. The arrows indicate PO’s direction. Bold names indicate POs reported for the first time in this study. Anthropogenic crosses are highlighted in light-blue. Parents of foreign origin contributing into spontaneous crosses are highlighted in yellow with their alleged geographic groups. Parents from the cluster of Muscat varieties are highlighted in brown. Red connectors refer to still doubtful PO direction. Connectors without arrow refer to PO without direction.

FIGURE 2

The resulted main founders of the traditional cultivated germplasm are scattered along the Italian peninsula according to their influence geographic areas. Green highlighted area: south-western Italy (IT-SW); Brown area: Italian Adriatic Coast (IT-AC) area of diversification; Red area: north-western Italy (IT-NW) area of diversification; Blue: Italian Northern Borders; Dotted arrows: the direction of the supposed genetic flow related to “Visparola” (red) and “Sangiovese” (blue) along the Italian peninsula, and to “Visparola” in the Balkans; Black arrows: introgression of varieties from outside areas; and Brown arrows: connections among some Italian regions with the Italian main centers of diversification. Map of Italy by Vemaps.com.