Effect of GA3 Concentration and Frequency on Yield and Quality of Zark Grape

A field experiment was carried out in a private vineyard located at Kamaki village, Duhok governorate, Kurdistan region, Iraq, during 2012 growing season to investigate the effect of four concentrations (0, 10, 20 and 30 ppm) and three frequencies (single, double and triple) of GA3 on yield and quality of Zark grapes. The results indicated that GA3 concentration and frequency significantly affected most studied traits. Increasing concentration and frequency of GA3 tended to increase yield per vine in term of number of clusters, cluster weight, number of berries per cluster and size of 100 berries. Juice percentage and density, total soluble solids, total sugars were also increased. However, total acidity and total phenols were significantly reduced. Weight of 100 berries was significantly affected only by increasing GA3 concentration. The interaction between 30 ppm GA3 and spraying triple surpassed all the traits studied in this investigation except size of 100 berries, total acidity and total phenols.