Late shoot pruning improves wine quality of field grown Vitis vinifera cv. Malbec.

Pruning is a common agrotechnical practice in vineyards, directly affecting the vegetative and reproductive development of the vines. The present research deals with a relatively new agrotechnical method of pruning termed "late shoot pruning" (LSP), or "late pruning". This method of pruning is performed in the spring (April) after budburst have occured. The purpose of the study was to examine the effect of three dates of pruning on the phenological development, canopy area, and vines physiology performance.

The study was conducted in a commercial vineyard near Mevo Horon planted with Vitis vinifera cv. Malbec, for two consecutive yeras (2016-2017). Five treatments were tested:

1. Winter pruning.

2. Winter pruning and cluster thinning (one cluster per shoot).

3. LSP performed 7 days after budburst.

4. LSP performed 14 day after budburst.

5. LSP performed 21 day after budburst.

The findings suggested that LSP significantly affected the phenological development of the vines. The LSP lead to a delay of the onset of budburst, which was manifested later in the season in delayed development of canopy. The younger leaves showed an improved carbon fixation and stomatal conductance, as well as a less negative midday stem water potential. In addition, we observed a phenomenon of "natural" cluster thinning due to the application of LSP treatments. These effects eventually resulted in improved must and wine parameters as reflected in the significantly higher wine tasting scores of the LSP treated vines.

Post-budburst pruning practice was found to have a positive effect on physiological and agrotechnical indices and on the quality of wine obtained, compared to standard pruning (with and without cluster thinning) in the Malbec cultivar. This study has significant commercial implications for the grape and wine industry, since performing a simple and inexpensive practice at the proper timing affects thinning of the cluster, saves labor, and improves the quality of the final product.