Effect of Chlormequat Chloride Application on Vegetative Growth and Overall Quality of Grape Cultivars Under Protected Cultivation

Growing grapevines under cover is an effective alternative to protect the berries from pre-monsoon rains in North Indian conditions. However, excessive vegetative growth under such conditions necessitates the use of growth retardants to enhance fruit quality and productivity. Chlormequat chloride (CCC) is one of the most widely used gibberellin biosynthesis inhibitors. The present research work was aimed at evaluating the effect of CCC (0, 250 ppm, 500 ppm, 750 ppm, and 1000 ppm) on three grape cultivars 'Perlette', 'Flame Seedless', and 'Punjab Purple' grown under a polyhouse. Vines were sprayed with an aqueous solution of CCC at the five-leaf stage (BBCH 15). Results revealed that exogenous application of CCC effectively retarded the cane and internodal length with a simultaneous increase in cane thickness. Among the cultivars, the maximum reduction in cane length (28.1%) and increase in cane diameter (22%) was recorded in 'Perlette'. CCC application reflected a significant decline in endogenous gibberellic acid content, improvement in soluble solids content (SSC), SSC:titratable acidity (SSC:TA) ratio, total and reducing sugars, and anthocyanin content in all studied grape cultivars. However, CCC application did not have a significant influence on TA or non-reducing sugars. Among all the treatments, CCC application at 750 ppm and 1000 ppm can be effectively applied on vines at the five-leaf stage (BBCH 15) to enhance the fruit quality of grape cultivars 'Perlette', 'Flame Seedless', and 'Punjab Purple' under polyhouse.