Abstract:

In order to investigate the effects of exogenous γ-aminobutyric acid（GABA）on the photosynthetic pigment and sugar content of leaves and fruit flavor quality in wine grape‘Cabernet Gernischt’，GABA solution with different concentrations（5，10，15 and 20 mmol · L^-1）was sprayed on the leaves at the flowering stage，fruit setting stage，enlargement stage and veraison stage，and distilled water was sprayed as the control. Photosynthetic pigment and sugar content of leaves at different stages and fruit flavor quality at the ripened stage were determined. Flavor quality of fruits was comprehensively evaluated and analyzed by using the PEN3 electronic nose non-destructive detection technology and gas chromatography-mass spectrometry（GC-MS）technology combined with cluster analysis，linear discriminant analysis（LDA），principal component analysis（PCA）and correlation analysis. The results showed that GABA treatment increased the contents of chlorophyll，carotenoids，soluble sugar and starch of the leaves of‘Cabernet Gernischt’grape and improved the flavor quality of the fruit. Notably，the total chlorophyll content in 10 mmol · L^-1 GABA-treated leaves was significantly higher than that of the control at different developmental stages. After treatment with 10 mmol · L^-1 GABA，the soluble sugar content of ripened grape fruits increased by 9% compared to the control group，while the levels of oxalic acid and tartaric acid showed respective increments of 121% and 108%. Compared with the control，GABA treatment increased the variety and content of fruit aroma volatiles. The aroma substances in fruits treated with different concentrations of GABA were similar in types，but showed significant difference in contents. The aroma profiles obtained by electronic nose analysis were basically consistent with that by GC-MS analysis. Among the different concentrations used in this study，10 mmol · L^-1 GABA treatment had the highest content of volatile aroma substances，as well as the higher sensitivity response values for most sensors. PCA and LDA analysis showed that the electronic nose detection results could better distinguish the flavor of‘Cabernet Gernischt’grape fruits treated with different concentrations of GABA. The correlation analysis showed that the contents of soluble sugar，starch in leaves and fruit sugars and organic acids have correlation with the formation of aroma substances in fruit. In summary，exogenous GABA treatment improved the flavor quality of the fruit by enhancing the contents of photosynthetic pigments，soluble sugar and starch in leaves and prompting the accumulation of sugars and organic acids and aroma volatiles in grape fruits；10 mmol · L^-1 was chosen as the optimum concentration of GABA.

Key words: grape, γ-aminobutyric acid, physiological characteristics, electronic nose, quality and flavor