Impact of temperature and sunlight on the skin coloration of the ‘Kyoho’ table grape

• Impact of temperature and sunlight on skin coloration of grapes was evaluated.
• Skin coloration was sufficient in berries at low temperature/sun-exposed treatment.
• Skin coloration was suppressed in berries at high temperature/shaded treatment.
• Temperatures 27 °C during ripening season led to insufficient berry coloration.

We evaluated the impact of increased temperature and sunlight exposure, features of global warming, on the skin coloration of ‘Kyoho’ table grape berries. Skin coloration, anthocyanin accumulation, abscisic acid (ABA) content, and transcript levels of anthocyanin biosynthetic genes in the skins were examined during the ripening season under continuous 24 °C, 27 °C and 30 °C temperatures together with a sun or shade treatment. Skin coloration and anthocyanin accumulation were sufficient in the berries of plants ripened at 24 °C with a sun-exposure treatment. They also had higher ABA contents and anthocyanin biosynthetic gene transcript levels than grapes under higher temperatures. The skins of grapes ripened at 27 °C or 30 °C showed insufficient coloration and low levels of anthocyanin accumulation, ABA content, and anthocyanin biosynthetic gene transcripts levels, irrespective of the light conditions. These results suggest that temperatures exceeding 27 °C during the ripening season lead to insufficient berry coloration as a result of low levels of ABA and anthocyanin biosynthetic gene expression levels.