Effect of bunch load on yield, quality and biochemical changes in Sharad Seedless grapes grafted on Dog Ridge rootstock.

Abstract

A field experiment was conducted during the year 2007-08 to study the effect of bunch thinning on bunch yield, berry quality and biochemical changes in Sharad Seedless table grapes. Crop load level was adjusted to 30, 40, 50, 60, 70, 80 and 90 bunches per vine. Significant differences were observed for all physicochemical and biochemical parameters except shoot diameter, inter nodal length and berry length. Average bunch weight was increased (466.02 g) with the reduction in number of bunches per vine (30 bunches). The same trend was also observed for average berry weight. Highest berry diameter (20.20 mm) was recorded in 30-bunch treatment followed by 19.90mm in 40-bunches per vine treatment whereas with the highest bunches per vine treatment (90-bunches/vine) the berry diameter was reduced to 17.50mm. It was observed that the reduction in bunch load per vine resulted into increase in total soluble solids in berries up to 18.500 Brix. Significant differences were recorded for reducing sugar, total phenols, proteins and total carbohydrate. The carbohydrate concentration was increased with the increase in number of bunches, however, the concentration was more in berries than in the rachis. Reducing sugar and starch was reduced with the increase in bunch load. Negative correlation of yield per vine with average bunch weight and berry weight was recorded. With the increase in number of bunches per vine, the yield per vine was also increased. The source: sink alteration by bunch removal had impact on yield, berry quality, sugar accumulation and berry composition. Considering the berry diameter as main quality parameter and the concentration of carbohydrate content, reducing sugar, starch and in berries and total phenols in the rachis, retention of 50 bunches per vine for the purpose of local market seems to be an ideal one.