Vine performance and grape composition as affected by early-season source limitation induced with anti-transpirants in two red Vitis vinifera L. cultivars.

Previous work has shown that an early (i.e. pre-flowering) source limitation achieved with either hand or mechanical basal shoot zone defoliation is effective in controlling yield while improving grape composition in several environments and Vitis vinifera genotypes. Our study was designed to determine whether similar results can be reproduced by using a film-forming anti-transpirant. Methods and Results: The entire canopies of field grown cvs. Sangiovese and Ciliegiolo vines were treated twice pre-flowering with the anti-transpirant Vapor Gard (R) (Intrachem Bio Italia, Grassobbio, BG, Italy) (T) and compared with an unsprayed control (C). Leaf assimilation and transpiration in both cultivars showed similar reductions (30-70%) for several weeks after spraying as compared with control vines, while intrinsic water use efficiency increased in treated vines soon after first application and after veraison. In Sangiovese, treated vines showed reduced yield, berry weight, bunch compactness and, on a 2-year basis, lower vigour and unchanged vine capacity every year. At harvest, treated vines showed higher degrees Brix in all seasons and higher anthocyanin concentration in 2 out of 3 years. Results of a 2-year run in Ciliegiolo mimicked those of Sangiovese in terms of yield regulation. Conclusions: Early season applications of a film-forming anti-transpirant caused a leaf function limitation strong enough to reduce yield and bunch compactness through smaller final berry size. Significance of the Study: Anti-transpirant applications can be proposed as a much easier way than manual or mechanical leaf removal to induce crop regulation through early source limitation.