Effect of Cane Regulation and GA 3 Spray on Berry Thinning in 'Thompson Seedless' Grape ( Vitis vinifera L.)

A field trial was conducted during 2013-14 and 2014-15 fruiting seasons in growers' vineyards around Nashik, Maharashtra, India to improve efficacy of GA₃ sprays in berrythinning. As smaller clusters have fewer berries, cluster compactness derived at by number of berries per unit length (cm) of rachis, and, berry-diameter were considered as a measure of berry-thinning. As GA₃ effect in berry-thinning is stage-specific, canes uniformly thick in a vine only were retained to achieve uniformity in flowering, by inducing uniform bud-break. Cane regulation did not result in uniformity in bud-break or flowering. Blanket spray of GA₃ thrice @ 20g a.i./ha, each coupled with either removal of non-uniform canes or retention of all the canes could effectively reduce cluster compactness by reducing number of berries per cluster, without increasing total length of the rachis/cluster or berry diameter. Vine yield and quality in terms of total soluble solids and acid content were not affected by the treatments. Considering cluster-compactness, yield and ease of cultural operations, retention of all the canes in a vine, coupled with three blanket sprays each of GA₃ @ 20g a.i/ha, on alternate days commencing from initiation of the bloom, is recommended for 'Thompson Seedless'.