EFFECT OF CROP LOAD AND CLUSTER THINNING ACCORDING TO ITS SHAPE ON CLUSTER WEIGHT AND YIELD ON 'THOMPSON SEEDLESS' TABLE GRAPES

The study was conducted on two consecutive seasons (2007-2008 and 2008-2009) to determine if crop load adjustment and cluster tipping in relation to cluster shape can allow an increase in cluster weight and yield per plant in ‘Thompson Seedless’ table grapes. During the first season the feasibility to classify clusters – prior to cluster thinning – as cylindrical, spherical or conical, was evaluated. Once feasibility was validated a crop load experiment was conducted, regulating crop load depending on the percentage of cylindrical clusters. Additionally, a cluster-tipping trial combining crop load with cluster shape and berry number was carried out. Results indicated that ‘Thompson Seedless’ plants with higher percentage of cylindrical clusters have lower yields; increasing cluster number per plant and berry number per cluster increase yield; and spherical and conical clusters on ‘Thompson Seedless’ present greater berry weight and size. These results can benefit ‘Thompson Seedless’ table grape vineyards management to optimize crop load adjustment in relation to yield and grape quality.