Variation in the Response of Thompson Seedless Grapes and its Clones to Chemical Thinning

Abstract

Field trial was conducted during 2013-14 and 2014-15 fruiting seasons in growers’ vineyards around Nashik, Maharashtra, India with an aim to study the variation in response to i) removal of un-uniform canes in bringing out uniformity in flowering, and ii) GA 3 sprays to reduce cluster compactness in Thompson Seedless and its clones, namely Tas-A-Ganesh and 2A Clone, and evolve a suitable package of producing loose to well-filled clusters without affecting yield and quality for each variety. Cane removal resulted in less uniform flowering. Flowering was more uniform in Thompson Seedless and 2A Clone in 2014-15 than in 2013-14. Uniformity in flowering was independent of uniform bud break. Cluster compactness was reduced by either removal or retention of canes in combination with three sprays of GA 3 @ 20 g a.i./ha or two sprays @ 30 g a.i./ha given just prior to the initiation of bloom, compared to growers’ practice of retaining all canes coupled with a single spray of 80 g a.i./ha at 50 per cent bloom in Thompson seedless and Tas-A-Ganesh, but not in 2A Clone. Cluster compactness obtained with growers’ practice in this variety was at par with that obtained by any treatment in other varieties. While increased rachis length contributed to less compactness in Thompson Seedless, it was the less berry diameter in 2A Clone. Yield/vine was comparatively less in Tas-A-Ganesh. Cane removal coupled with three sprays of GA 3 @ 20 g a.i./ha reduced the yield. Berry quality, in terms of more TSS and less acidity, was better in 2A Clone. For uniform flowering, components of cluster compactness and yield and quality of berries were more favourable in 2014-15 season than 2013-14. Treatment effects were accentuated by their interaction with season and variety. Considering together the yield and quality with cluster compactness, it can be concluded that, retention of all canes coupled with spraying GA 3 twice @ 30 g a.i./ha is ideal for the varieties studied under the conditions of experimentation.