Abstract:

In order to investigate the effects of exogenous fulvic acid potassium（FA-K）on sugar-acid metabolism and aroma substances in wine grape berries. In this experiment，‘Cabernet Gernischt’grapes were used as the experimental material，which were treated with 30，60，90 and 120 mg · L^-1 FA-K solution treatments，with water as control treatment，were applied as foliar sprays at anthesis，fruit set，fruit expansion and color change stages. The effects of FA-K on the content of sugar，acid components and aroma substances as well as the activities of related metabolizing enzymes were determined during the different reproductive periods of grapes. The results showed that FA-K treatment promoted the accumulation of total soluble sugar，glucose，fructose and sucrose content. Especially，the effect of 90 mg · L^-1 FA-K treatment was the most significant. The content of sugar components in the fruit reached the peak at the mature stage，and increased by 25.96%，30.04%，41.48% and 36.17%，respectively compared with the control，while the content of organic acids（malic acid，tartaric acid，oxalic acid and citric acid）in the fruit decreased under different concentrations of FA-K treatment. In addition，FA-K treatment favored the activities of sucrose synthase synthesis direction（SS-ss），sucrose phosphate synthase（SPS），NADP-malic enzyme（NADP-ME），NAD-isocitrate dehydrogenase（NAD-IDH）and mitochondrial aconitase（Mit-ACO），and decreased the activities of sucrose synthase decomposition direction（SS-sc），acid invertase（AI），neutral invertases（NI），phosphoenolpyruvate carboxylase（PEPC），NADP-malate dehydrogenase（NAD-MDH），citrate synthase（CS）and cytoplasmic aconitase（Cyt-ACO）. A total of 51 aroma substances were detected in‘Cabernet Gernischt’grape berries using GC-MS，among which n-hexanal，n-hexanol，cyclohexyl formate，2-hexenal and 2-cyclohexen-1-ol were the main aroma components. There were some differences in the aroma substances and contents of fruits with different concentrations of FA-K treatment，among which 90 mg · L^-1 treatment had the most obvious effect on ketones，alcohols，aldehydes，esters and phenolic the aroma components were increased by 1，3，1，1 and 1，and the contents were increased by 650.39%，321.45%，233.93%，127.65% and 125.07%，respectively，in comparison with the control treatment. In conclusion，FA-K treatment can improve the activity of key enzymes of sugar and acid metabolism in wine grape berries to promote the accumulation of sugar and acid components in berries，and has a positive effect on the accumulation of aroma substances in berries，which significantly improved the flavor quality of berries，and the effect of 90 mg · L^-1 FA-K treatment was the most significant.

Key words: wine grape, potassium fulvic acid, glucose, acid, metabolism, quality, flavor