Effect of gibberellic acid spraying and girdling on the improvement of the quantity and quality characteristics of  Yaghooti seedless grape

In the current study، for improving quality and quantity of ‘Yaghooti’ seedless grape، gibberellic acid was sprayed in four concentrations including zero (as control)، 15، 25 and 40 mg/l، at three stages، and girdling treatments were carried out simultaneously with the third step of GA3 spraying at the base of fruit bearing shoots with four replications. The cluster length was significantly increased by all three concentrations of GA3 in compare with the control. In fact، 14 days after GA3 spray، the cluster length respectively grew to 17. 87، 19. 73 and 23. 95 cm at 15، 25 and 40 mg/L GA3، whereas، in the control sample it was 13. 46 cm. Furthermore، the berry and cluster weight were increased by foliar application of GA3 and girdling in which the maximum berry weight (1. 42 gr) and cluster weight (483. 7 gr) were achieved by interaction of 40 mg/l GA3 and girdling. In addition، girdling treatment significantly led to the increase of the berry length and width as compared to control sample; however، for some traits there was not any meaningful treatment. Application of GA3 and girdling treatment significantly led to the increase of the TSS/TA ratio in compared to control.