title: Effects of Leaf Removal and Applied Water on Flavonoid Accumulation in Grapevine (Vitis vinifera L. cv. Merlot) Berry in a Hot Climate.
abstract: The relationships between variations in grapevine (Vitis vinifera L. cv. Merlot) fruit zone light exposure and water deficits and the resulting berry flavonoid composition were investigated in a hot climate. The experimental design involved application of mechanical leaf removal (control, pre-bloom, post-fruit set) and differing water deficits (sustained deficit irrigation and regulated deficit irrigation). Flavonol and anthocyanin concentrations were measured by C18 reversed-phased HPLC and increased with pre-bloom leaf removal in 2013, but with post-fruit set leaf removal in 2014. Proanthocyanidin isolates were characterized by acid catalysis in the presence of excess phloroglucinol followed by reversed-phase HPLC. Post-fruit set leaf removal increased total proanthocyanidin concentration in both years, whereas no effect was observed with applied water amounts. Mean degree of polymerization of skin proanthocyanidins increased with post-fruit set leaf removal compared to pre-bloom, whereas water deficit had no effect. Conversion yield was greater with post-fruit set leaf removal. Seed proanthocyanidin concentration was rarely affected by applied treatments. The application of post-fruit set leaf removal, regardless of water deficit. increased the proportion of proanthocyanidins derived from the skin, whereas no leaf removal or pre-bloom leaf removal regardless of water deficit increased the proportion of seed-derived proanthocyanidins. The study provides fundamental information to viticulturists and winemakers on how to manage red wine grape low molecular weight phenolics and polymeric proanthocyanidin composition in a hot climate.
authors.affiliation: Department of Viticulture and Enology, Oakville Experiment Station, University of California , Oakville, California 94562, United States.
authors.forename: Runze
authors.initials: R
authors.lastname: Yu
authors.affiliation: Texas A&M AgriLife Extension Service , 401 West Hickory Street, Denton, Texas 76201, United States.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Cook
authors.affiliation: Gusmer Enterprises, Inc. , 124 M Street, Fresno, California 93721, United States.
authors.forename: Ralph S
authors.initials: RS
authors.lastname: Yacco
authors.affiliation: Department of Viticulture and Enology, Oakville Experiment Station, University of California , Oakville, California 94562, United States.
authors.forename: Aude A
authors.initials: AA
authors.lastname: Watrelot
authors.affiliation: 3UMR EGFV ISVV , 210 Chemin de Leysotte, CS 50008, 33882 Villenave d'Ornon Cedex, France.
authors.forename: Gregory
authors.initials: G
authors.lastname: Gambetta
authors.affiliation: Constellation Brands, Inc. , 12667 Road 24, Madera, California 93637, United States.
authors.forename: James A
authors.initials: JA
authors.lastname: Kennedy
authors.affiliation: Department of Viticulture and Enology, Oakville Experiment Station, University of California , Oakville, California 94562, United States.
authors.forename: S Kaan
authors.initials: SK
authors.lastname: Kurtural
mesh_terms: D057914:Agricultural Irrigation; D000383:Agriculture / Q000379:methods*; D000872:Anthocyanins / Q000378:metabolism; D002140:California; D002980:Climate; D005419:Flavonoids / Q000378:metabolism*; D044948:Flavonols / Q000378:metabolism; D005638:Fruit / Q000378:metabolism; D008970:Molecular Weight; D018515:Plant Leaves; D044945:Proanthocyanidins / Q000737:chemistry / Q000378:metabolism; D012639:Seeds / Q000737:chemistry / Q000378:metabolism; D027843:Vitis / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D014887:Weather
chemical_list: D000872:Anthocyanins; D005419:Flavonoids; D044948:Flavonols; D044945:Proanthocyanidins; C013221:proanthocyanidin
keywords: anthocyanins; applied water amount; flavanols; flavonols; leaf removal; viticulture practices; water deficit