Effect of potassium phosphite and boric acid on fruit set in different grape (Vitis vinifera L.) cultivars

In order to study the effect of potassium phosphite and boric acid on fruit set of different grape (Vitis vinifera L.)cultivars,two separate experiments were arranged in a factorial design based on a completely randomized design with 3 replications on orchard conditions. The first experiment was involved foliar application of potassium phosphate (0, 1500 and 3000 mg/L) on Askari, Sefidali and Razeghi cultivars and in second trail spraying of boric acid (0, 1500 and 3000 mg/L) after 50% anthesis on inflorescence were done on same cultivars. The total number of flowers, number of opened and closed flowers, number of fallen flowers, and the number of flowers after abscission and fruit set in all three cultivars were measured. The results showed that there was a significant difference at P≤0.01 for all or some of traits between Askari, Sefidali, Razeghi cultivars and between three concentrations of potassium phosphate and boric acid. The lowest number of flower abscission (44.69 and 51.85) and highest fruit set (74.58 and 77.60%) were obtained from potassium phosphate and boric acid treatments with 3000 mg/L, respectively. According to the results of this study and also regarding to other important traits and experiment conditions, potassium phosphate and boric acid fertilizers at 3000 mg/L after 50% anthesis are suggested due to the positive effects on increases fruit set and crop yield as.