| Resumo: |
ABSTRACT In climate region Cwa of the State of São Paulo the technique of double cropping the grapevine is possible, however, when it is time for the second pruning of the crop, most of the vine’s leaves are still in the plant, posing the problem that the use of ethephon as a defoliant could increase leaf senescence and improve the vine management. The objective of this study was to evaluate the effects of ethephon spray as a defoliant in the development and production of the ‘Niagara Rosada’ vine when subjected to double cropping, and the influence this bioactivator may have on carbohydrate reserves in the branch. The experiments were conducted in a commercial, non-irrigated area in agricultural years of 2011/2012 and 2012/2013. The length, diameter and total carbohydrate reserves of the branches, as well as bud break, number of clusters, crop production, length, width and mass of cluster, berry diameter, soluble solids and titratable acidity were evaluated. Ethephon treatments were applied at a concentration of 1,440 mg L-1 and 2,160 mg L-1 at 20 and 15 days before pruning. As a control, the vines were defoliated by hand at the time of pruning. A randomized block experimental design was used. Data was subjected to analysis of variance and means were compared by the Tukey test at 5% significance level. In conclusion, we propose that ethephon sprays promoted vine defoliation and improved the bud break, altered plant development and crop production. This was not due to increases in concentration of carbohydrate reserves in the branches, but due to a higher induction stimulus of bud break, which allowed the vines to express their higher yield capacity.
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