Light irradiation with different wavelmengths modifies the quality traits and monoterpenes biosynthesis of postharvest grape berries during the shelf life

Monoterpenes are the most important contributors to the floral and fruity flavor of Muscat grapes. However, loss of Muscat flavor and decreased quality during shelf life often affect the commercial value of grapes. Light radiation can be an effective tool to maintain postharvest quality. In the present study, the effect of different wavelengths of light (white, red, blue, red-blue, UV-A and UV-B) on the quality of 'Shine Muscat' (Vitis labrusca x vinifera) during the shelf life was carried out. Grapes irradiated with white, red, blue and red-blue light showed degraded chlorophyll and accumulated carotenoids in the skin compared to grapes under dark conditions. Blue and red-blue light were more effective than other wavelengths of light in maintaining and increasing the levels of monoterpenes, such as linalool, limonene, and geraniol. Blue light exhibited the best maintenance and promotion effects on overall quality based on principal component analysis, and promoted the expression of some key genes involved in monoterpene synthesis, such as VvPNLinNer 1, VvPNLinNer 2, VvTPS60 and VvPNLNGL4. The transient over-expression experiment revealed that VvTPS60 may be primarily responsible for catalyzing the linalool synthesis. Results suggest that exposing postharvest grapes to different wavelengths of light is a promising technology to improve fruit quality.