Study of intra-varietal diversity in biotypes of Aglianico and Muscat of Alexandria (Vitis vinifera L.) cultivars

Background and Aims: Somatic mutations are the major source of intra-varietal variability in some species such as grapevine (Vitis vinifera L.) that are propagated vegetatively. Aglianico and Muscat of Alexandria are two cultivars mostly cultivated in the south of Italy, showing great intra-varietal diversity. The variability of 15 clones of Aglianico belonging to three biotypes, Taburno, Taurasi and Vulture, and 21 clones of Muscat of Alexandria, coming from France, Greece, Italy and Spain, was investigated. Methods and Results: The intra-varietal diversity was investigated by ampelographic and eno-carpological (berry characteristics of oenological interest) methods (nine OIV descriptors, related to bunch and berry morphology, sugar content, total acid content and pH of must), chemical (anthocyanins, aromatic compounds and phenolic substances) and genetic analysis [18K SNPs, single nucleotide polymorphisms (SNP)]. Intra-varietal diversity has been detected in both cultivars, mainly based on differences in the accumulation of secondary metabolites. The Taurasi biotype was discriminated by linear discrimination analysis mainly for the proportion of malvidin-3-O-glucoside acetate and methoxylated anthocyanins, while the Spanish Muscat biotype was discriminated based on the proportion of flavanols and hydroxycinnamic acids. Conclusions: Ampelography and the concentration of secondary metabolites have proved to be the best tools for the characterisation of the intra-varietal variability of grapevine germplasm. The high-throughput genetic analysis based on 18K SNP loci did not highlight a polymorphism sufficient to distinguish among biotypes of the same cultivar, suggesting that a different molecular approach has to be adopted. Significance of the Study: This study confirms that intra-varietal diversity is better examined with a multidisciplinary approach.