Unravelling the identities of grapevines: state of art and future perspectives

Clizia Villano, Riccardo Aversano [Dipartimento di Agraria, Università di Napoli Federico II]

Cultivated grapevine, Vitis vinifera subsp. vinifera L., is one of the most widely grown fruit crops in the world. Sexual hybridization has been a major driving force for its evolution and has generated thousands of varieties, whereas somatic mutations are the major source of intra-varietal grapevine diversity.
Nowadays, more than 450 varieties are registered in Italy, and thousands of clones are recognized. All these grapes are proudly used to make some of the world’s finest wines, thanks not only to history, traditions, and excellent pedo-climatic conditions but also to a particularly heterogeneous collection of varieties, some of which have been growing here since the first half of the 19th century. However, in the past few decades the grapevine biodiversity has been eroded, due to the worldwide predominance of few successful cultivars and to cultivation restrictions for varieties not included in official grapevine lists. Therefore, there is a significant decrease of raw material for future selection and to address new breeding objectives. An efficient characterization system is important to define population structures, to avoid cases of synonymy (ident ical genotypes but di f ferent names) and homonymy (same names but different genotypes), and protect breeders’ rights. The oldest grape discrimination techniques are based on phenological traits analysis carried out during all vegetative cycle. These techniques are elaborate and time-consuming.
Characterization of grapevine has today been complemented by the use of DNA-based techniques, which enables more accurate identification and overcomes many of the limitations of phenotypic-based diversity analysis. Through the exploitation of molecular markers, many cases of synonymies/homonymies have been ident i f ied in the Italian collections. However, when molecular markers have been used to study clonal variation, consistent results have not always been obtained. The plethora of high-throughput technologies currently available provides promising tools for the analysis of diversity within the varieties.
Moreover, the anticipated improvements in NGS capacity will lead to further decrease the persample cost and increase the quality of the resulting genotype data. In this scenario, the objective of this paper is to review on varietal authentication methods with particular emphasis on those capable to distinguish clones within variety populations. After reporting the causes and consequences of genetic inter- and intra-varietal diversity, we will review the methodologies currently applied to unraveling them. We then provide information on the potential of post-genomic techniques as powerful tools to identify synonymous and homonymous cases and to distinguish clonal populations.

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