Effect of pre harvest ethephon spray on color and some quality attributes of grape (Vitis vinifera L. cv. Bidane- Ghermez)

Grape is non-climacteric fruit and as a result, the quality of fruit does not change after harvest. Application of ethephon in recent years is known as an effective way to increase the quantity and quality of grape. In this study, the effect of pre harvest application of ethephon at four levels (0, 150, 250 and 300 mg/l) and ethephon treatment time at two levels (10-20% and 50-70% of berry veraison) were evaluated on quality indices of Bidane -Ghermez grape cultivar at harvest time. The experiment was carried out with a factorial design in a randomized complete block with three replications. Evaluated indices were soluble solids content, titratable acidity, palatability, pH, ascorbic acid content, tissue firmness and fruit color. Application of ethephon increased soluble solids content, ascorbic acid content, palatability and fruit color but had no effect on pH. Colorimetric results showed that ethephon treatment reduced L parameter, Hue angle and Chroma and increased a/b ratio. Titratable acidity and tissue firmness were decreased with application of ethephon. Results showed that spray of 150mg/l ethephon at 50-70% of berry veraison increased soluble solids content, palatability and fruit color but had no more effect on reducing tissue firmness. Based on the obtained results, application of ethephon with the optimum concentration in the proper time can be an effective strategy to improve color and optimum quality of berries.