Abstract
The major limitation of the very early ripening Vitis vinifera cv. Early Sweet is its cluster compactness and significant variability of berry size. In the current study, we tested the ability of abscisic acid (ABA) to reduce the number of berries per cluster and improve berry size uniformity. Data collected from a commercial vineyard, in three successive growing seasons, suggest that ABA application: (1) induces a significant reduction in berry number per cluster, in a concentration-dependent manner; (2) improves uniformity of berry size within a cluster; (3) has no significant effect on rachis length. The results also suggest that the thinning effect of ABA depends on the bloom status of the inflorescence, with limited or no effect when applied at pre-anthesis, and a very significant effect when applied at full bloom and soon after the anthers are detached. Accordingly, the effect of a semi-commercial application of ABA on number and size of berries was significantly affected by asynchronous blooming. Completion of bloom may serve as a clear phenological marker for optimal application timing that allows uniform and effective thinning.
- ©2017 by the American Society for Enology and Viticulture
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