Abstract
The first serious outbreak of Flavescence dorée (FD) in Piedmont (North-West Italy) dates back to 1998 in the Tortona area (Alessandria province). FD is a serious quarantine-worthy disease transmitted by the leafhopper Scaphoideus titanus Ball. Different Vitis vinifera L. biotypes react differently to the phytoplasma, in particular as to the accumulation of polyphenols in leaves. In this experimentation, we observed and described concentration and accumulation of the main classes of polyphenols in entire leaves and in leaf blades and veins of two varieties, Nebbiolo and Barbera, displaying different levels of susceptibility to FD. Their well-known different reactions could be related, at least partially, to leaf polyphenols, both as to concentrations and profiles. Nebbiolo displayed some specific traits: i) the higher percentage of incidence over totals of individual molecules known to be powerful antioxidants (caftaric acid over coutaric acid; quercetin glycosides over other flavonols); ii) the higher concentration of flavanols in veins with respect to Barbera and their wider profile (astilbin and a taxifolin-glycoside, this last accumulating exclusively in Nebbiolo).
Highlights
The first important outbreak of Flavescence dorée (FD) in Piedmont (North-West Italy) occurred in 1998; since that year FD has become a serious problem for Piedmont’s regional viticulture, which has imposed compulsory sprays against the vector, the leafhopper Scaphoideus titanus Ball
The activation of the phenylpropanoid pathway following FD infection was evident in both varieties, and in Barbera the chalconesynthase 3 encoding gene (CHS3) was up to 20-fold upregulated than in Nebbiolo; genes encoding hydroxylases, UFGT, VvMYBA1 and LAR were upregulated in infected Barbera leaves with respect to Nebbiolo
HCTA concentration in FD-infected Barbera leaves increased during the season both when considering the entire leaf (Fig. 2) or veins and blades separately (Fig. 3)
Summary
The first important outbreak of Flavescence dorée (FD) in Piedmont (North-West Italy) occurred in 1998; since that year FD has become a serious problem for Piedmont’s regional viticulture, which has imposed compulsory sprays against the vector, the leafhopper Scaphoideus titanus Ball. The activation of the phenylpropanoid pathway following FD infection was evident in both varieties, and in Barbera the chalconesynthase 3 encoding gene (CHS3) was up to 20-fold upregulated than in Nebbiolo; genes encoding hydroxylases, UFGT, VvMYBA1 and LAR were upregulated in infected Barbera leaves with respect to Nebbiolo. This resulted in a significantly higher anthocyanin, flavonol and proanthocyanidin content, at the end of the season (Margaria et al, 2014). Leaf blades and veins were analysed separately
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