Content of reserves, vegetative vigor and yield of grapevines submitted to two harvests per vegetative cycle

Abstract

This study evaluated the content of reserves in the branches and assessed the vegetative vigor and yield of Niagara Branca, Niagara Rosada and Concord grapevines submitted to two harvests per vegetative cycle. The plants were subjected to a winter pruning (WP) performed by means of a short pruning, and to a green pruning (GP) at the end of spring performed by pruning branches from the fourth bud above the last grape cluster. The treatments included Control 1 (WP on 07-20-07/no GP), Control 2 (WP on 0-22-07/no GP), T1 (WP on 07-20-07/GP on 11-15-07), T2 (WP on 07-20-07/GP on 12-17- 07), T3 (WP on 08-22-07/GP on 11-15-07) and T4 (WP on 08-22-07/GP on 12-17-07). The variables evaluated included grapevine production for the two crops, the leaf area index (LAI) throughout the vegetative cycle, and the content of reserves in the branches in the following stages: 2007 WP, first crop flowering, GP on 11-15-07, GP on 12-17-07, post-harvest of first and second crop, and 2008 WP. The WP associated to GP allowed to obtain two harvests in all cultivars being more effective in the T3. The shoots emitted by GP caused changes in the LAI and affected the dynamic of synthesis/ consumption of reserves in the branches of the grapevines. In plants with GP, there was reduction in the content of reserves at the end of the crop cycle compared to control plants. The pruning management to obtain two annual crops increased the annual production, but reduced the level of reserves of the grapevines.