Abstract
The effects of temperature on the color of detached ‘Ruby Roman’ grape berries at different developmental stages after véraison were investigated. The berries were collected from grapevines at 50 days after full-bloom (DAFB), 60 DAFB, 70 DAFB, and 80 DAFB, and incubated at 18°C, 21°C, 24°C, 27°C, and 30°C for ten days, respectively. The color chart value increased after treatment compared with that before treatment under all temperature conditions at 50 DAFB, 18–24°C at 60 and 70 DAFB, and 18°C at 80 DAFB. These results indicate that the color of ‘Ruby Roman’ grape berry skin is enhanced by exposure to lower temperatures after 60 DAFB, and that the closer the berry is to maturity, the higher is its requirement for low temperatures to achieve the desired color. We performed an analysis of abscisic acid (ABA) metabolites and expression of genes involved in anthocyanin biosynthesis in the berry skins. The findings of the analysis indicated that the exposure to high temperature (30°C) increased the biosynthesis of ABA and expression of the VlMybA1 genes. In addition, expression of the anthocyanin biosynthesis-related structural genes, such as VviF3′5′H2 and VviFAOMT, was more accelerated at a low temperature of 18°C at 50 and 60 DAFB than at 70 and 80 DAFB. Therefore, anthocyanin accumulation in ‘Ruby Roman’ berry skin under different temperature conditions is not directly related to the endogenous ABA concentration and VlMybA1s expression levels, but may be related to ABA signal transduction, the substrates of anthocyanin biosynthesis and activities of related enzymes, and (or) other different factors.
