Heat-treated v. virus-infected grapevine clones: Agronomical and enological modifications

The present report deals with the effects of heat-treatment on agronomical and enological performances of formerly virus-infected clones of Vitis vinifera Grignolino, Nebbiolo and Nebbiolo Michet cultivars grown in the Northwest of Italy. The elimination of leafroll and rugose wood had beneficial effects on clone performances although diversified depending on the viral agents involved. When the viruses eliminated were GLRaV-3 and GVA, grape quality was greatly improved thanks to higher juice soluble solids and berry skin anthocyanins, yield, however, was not influenced. When the material was propagated, vegetative vigour was also increased as well as nursery take. The improvement of grape quality shown in the field was maintained in the wine produced from healthy vines as confirmed by sensory evaluation. When the viruses involved were GLRaV-1 and GVA, sanitation was only effective in improving quantitative parameters (yield, berry and cluster size) and berry pigmentation. The elimination of fanleaf(GFLV plus GFkV) induced in the vines such a strong increase of vigour that vine fertility resulted reduced without any improvement of grape and wine quality. In addition, more summer pruning was needed with consequential higher costs.