Effects of gibberellic-acid and salicylic-acid on phytochemical characteristics, antioxidant capacity and nutrient elements of Bidane-Sefid grape

Grape berry is an excellent source of natural pigments and contains a large amount of different antioxidant compounds. The main characteristic of modern grape production is its compliance with the requirements of the target market, such as improved grape quality and high nutritional value. In addition, seedless grapes are important. The seedless grape varieties were greatly appreciated for their good taste and customer preference in the global market both fresh and raisin. Therefore, in order to improve the biochemical characteristics of the grape (Bidane-Sefid cultivar), effects of spraying gibberellic acid and salicylic acid on some qualitative traits, anti oxidant and nutrient elements of berry were studied.

This experiment in a factorial experiment was conducted based on randomized complete block design with two treatments and three replications to evaluate some of the qualitative traits (pH, TSS, TA, glucose, fructose, fructose to glucose ratio), antioxidant compounds (total phenol, total flavonoid, total anthocyanin, vitamin C, antioxidant activity, PAL enzyme, polyphenol oxidase enzyme and nutrient elements of berry (N-P-K-Ca- Mg-S-Fe-Zn-Cu- Mn-Br). Treatments included gibberellic acid at three levels (0, 40 and 80 mg L-1) and salicylic acid at three levels (0, 75 and 150 mg L-1).

The results showed that the treatments and their interaction effects on the studied traits were significant. But there was no significant effect of salicylic acid on the PAL enzyme. The amount of glucose and fructose of grape berries determined by HPLC were in the range of 88.66 to 151.74 and 72.92 to 132.66 (g kg-1), respectively. The highest total phenol content (43.77 mg 1ml-1 e), total flavonoid content (1.51 mg 1ml-1 e) and antioxidant activity by DPPH assay (86.02%) were observed in the interaction of sprayed samples with 40 mg L-1 gibberellic acid and non-use salicylic acid. The highest anthocyanin content (3.51 mg 1ml-1 e) and PAL enzyme activity (7.90 n mol cinnamic acid FW min-1) were observed in the interaction of sprayed berries with 80 mg L-1 gibberellic acid and 75 mg L-1 salicylic acid. Also, the results showed that the highest activity of polyphenol oxidase enzyme was observed in the interaction of treatment with 40 mg L-1 gibberellic acid and 75 mg L-1 salicylic acid. The highest of nitrogen (0.63%), phosphorus (0.14%), potassium (1.41%) and magnesium (0.05%) elements were found in the interaction of treatment with 80 mg L-1 gibberellic acid and 75 mg L-1 salicylic acid.

The results showed that the biochemical properties of grape berries can be improved using gibberellic acid and salicylic acid treatments. According to the results of this study, treatments containing gibberellic acid (especially GA40SA0) had more effects on the accumulation of antioxidant compounds and antioxidant activity than salicylic acid.