Study On Sugars And Acids Inheritance And The Expression Pattern Of β-glucosidase Genes (VvBGs) During Grape Berry Ripening

Two consecutive years’ measurement of the sugar and acid content among104grape varieties suggested that:the major sugar components in grape were glucose and fructose, and less sucrose. The content of glucose ranged from46.26to120.86mg ml-1; the content of fructose ranged from48.64to128.09mg ml-1; and the content of sucrose ranged from0to21.27mg ml-1. The major acid components in grape were tartaric acid and malic acid, which the content of the former was significantly higher than that of the later. The range of tartaric acid in two years were1.68～9.05mg ml-1and1.67～9.03mg ml-1, and the range of malic acid in two years were0.39～6.15mg ml-1and0.34～6.98mgml-1, respectively. There was a higher sugar level and a lower acid level in hybrids of American and European varieties. Two consecutive years’ analysis of the sugar and acid heritability in different types of filial generation showed that the average of sugar content in filial generation was lower than that in parent generation, and the propotion of transgressive segregation was low. There was a similar heritability between hybrids of Asian and European varieties and American and European varieties. The heritability of glucose was0.60～0.85, the heritability of fructose was0.57～0.75, and the heritability of total sugar was0.62～0.83. The total acid content was additive inheritance and was mainly influenced by malic acid, and the heredity of total acid was0.42～0.91.In order to understand more about the role of b-glucosidase gene expression in modulating ABA level, the expression pattern of three cDNAs (VvBG1, VvBG2and VvBG3) which encode b-glucosidase in ripening grape berries was analyzed in the presence or absence of dehydration stress. The results show that expression of these three VvBG genes was markedly different. Expression of VvBG1and VvBG2increased rapidly from ve’raison to reach a maximum at harvest or several days immediately before harvest, and coincident with ABA accumulation during berry development and ripening. However, expression of VvBG3differed from VvBG1and VvBG2in that transcript levels declined from the early young fruit stage through ve’raison after which there was no further change. At10days before harvest, dehydration treatment of detached grape berries up-regulated the expression of VvBG1and enhanced ABA accumulation whereas the expression of VvBG2was down-regulated, VvBG3was unaffected by dehydration stress. However, in the leaves, dehydration treatment up-regulated the expression of VvBG1and stimulated the accumulation of ABA but downregulated expression of VvBG2and VvBG3. Based on the results obtained, it is concluded that the expression pattern of the three VvBGs is both temporal and tissue specific.Furthermore, expression of the VvBGs might play a role in the regulation of ABA content during berry ripening and in the response of berries to dehydration stress.