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Daily Preharvest UV-C Light Maintains the High Stilbenoid Concentration in Grapes

Guerrero, Raúl F., Cantos-Villar, Emma, Puertas, Belén, Richard, Tristan
Journal of agricultural and food chemistry 2016 v.64 no.25 pp. 5139-5147
Vitis vinifera, disease resistance, harvesting, immunity, pesticides, phytoalexins, ripening, stilbenoids, table grapes, ultraviolet radiation, vineyards, viniferins
The fact that it is possible to induce stilbenoid synthesis in grapevine (Vitis vinifera) by UV-C light allows the possibility of stimulating grapevine phytoalexin production to increase disease resistance and immunity, and subsequently to limit the use of pesticides in vineyards. UV-C light was applied daily during three days before the harvesting of table grape variety Crimson seedless to study the accumulation of stilbenoid compounds during ripeness. The E-resveratrol concentration was monitored during daily preharvest UV-C light application and compared with that after a single application. Daily periodic preharvest UV-C light treatment showed a cumulative effect on grape stilbenoids. An 86-fold stilbenoid level increase (sum of E-resveratrol, E-piceatannol, ε-viniferin, E-piceid, isorhapontigenin, ω-viniferin, and Z-piceid) in grapes was achieved. The effects of UV-C light on stilbenoid in grape cane was also addressed for the first time. Stilbenoid oligomers such as hopeaphenol, ampelopsin A, and r-viniferin were quantified in cane samples. Quality grape parameters indicated an acceleration of ripening in UV-C samples.