Composition and Contents of Organic Acids in Different Grape Germplasms

In order to select excellent grape germplasms, the organic acid composition and content of 302 grape germplasms preserved in the Zhengzhou National Grape Germplasm Repository were analyzed by high performance liquid chromatography (HPLC). The obtained data were analyzed by cluster analysis (CA) and principal component analysis (PCA). The results showed that tartaric acid was more abundant than malic acid in 93.8% of the 302 samples, in 5.12% of these samples, malic acid content was similar to citric acid content (the difference between them did not exceed 2%), and 7.37% of the grape samples had higher malic acid content than tartaric acid content. In cultivated grapes, tartaric acid was more abundant than malic acid. For wild grapes (except Vitis davidii Fox.), the malic acid content of Vitis ficifolia, Vitis adenoclada Hand-Mazz, Vitis pseudoreticulata Wang Tian Wang and Vitis riparia was 1.2–1.7 times higher than the tartaric acid. Moreover, it was found that the organic acid content of wine grapes was significantly higher than that of grape accessions used for other purposes, and the pH (3.776) of table grapes was significantly higher than that of grape accessions used for other purposes. In addition, the content of organic acids in grape populations from East Asia, especially tartaric acid (8.325 mg/mL), was higher than that in other populations. The variation coefficients of tartaric acid content, total acid content and acidity among samples were small, while the contents of oxalic acid, malic acid and citric acid varied greatly among samples. Tartaric acid was significantly positively correlated with other organic acids but not with pH or oxalic acid. Total acid content was significantly positively correlated with the content of tartaric acid, oxalic acid, malic acid, citric acid, titratable acid and acidity value. The organic acid content of wild grapes was much higher than that of cultivated grapes. Notably, the organic acid content of Vitis amurensis Rupr. N43-3, belonging to the East Asian population endemic to China, was the highest. Therefore, wild grape resources can be used as special resources for breeding or directly utilized.