Effect of cluster thinning on bunch yield, berry quality and biochemical changes in local clone of table grape cv. Jumbo Seedless (Nana Purple)

A field experiment was conducted during the year 2011-2012 to study the effect of cluster thinning on bunch yield, berry quality and biochemical changes in black seedless local clone of table grape. Crop load level was adjusted to 23, 27, 33, 37, 45 and 50 clusters per vine. Significant differences were observed for all physico-chemical parameters except pH. Shoot length was positively correlated (0.98) with the internodal length. Highest bunch weight (673.0 g) was recorded at lowest crop load level (23 clusters per vine) and vice-versa. Highest berry weight (7.89 g) and berry diameter (24.78 mm) was also recorded at lowest crop load level, which resulted into increased in bunch weight. It was observed that the reduction in clusters per vine resulted into increase in total soluble solids in berries. Significant differences were recorded for reducing sugar, total phenols, total proteins and total carbohydrates. The concentration of reducing sugar was reduced with the increase in number of clusters per vine. With the increase in clusters per vine, carbohydrate content in berries was also reduced. Therefore, thinning upto 27 clusters per vine spaced at a distance of 3.0 m x 1.66 m is recommended for better yield, quality and returns to the grape growers.