BACKGROUND: The physiological and metabolic processes involved with grapevine growth and production are influenced by key macro- and micronutrients. Potassium is an essential plant nutrient that affects growth and fruit quality. In this study, the impact of foliar spraying of potassium sulfate (K2SO4) on qualitative characteristics of grape berrieswas evaluated in the cultivar ‘Rasha’, a commonly cultivated cultivar in Kurdistan province of Iran. Leaves of the fully grown vines were sprayed with each of the 1.5 and 3 g L−1 K2SO4 solutions once (1month after petal senescence) and twice (15 days after first spraying). The control plantswere sprayedwith distilledwater. Various biochemical contents and enzyme activities on the ripe berrieswere analyzed. RESULTS: Significant increases in anthocyanin, total protein content, and antioxidant enzyme activities were observed in the berries treated twice with 3 g L−1 K2SO4. Concentrations of total carbohydrate, phenol, and antioxidant activity in berries sprayedwithK2SO4 were higher thaninthecontrols.Weobserveda strongcorrelation betweenantioxidant activity anddifferent phenolic compounds. CONCLUSION: These findings suggest that K2SO4 treatment influences biosynthesis of phenolic compounds and antioxidant enzymes. Thus, treatment by K2SO4 could improve nutritional and qualitative attributes of grape.
