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Gael Benoteau and Andrew G. Reynolds

The potential for interference by specific C6 compounds in the colorimetric quantitation of grape (Vitis vinifera L.) monoterpenes was investigated in model solutions and muscat and neutral-flavored grape cultivars. The unsaturated C6 aldehyde 2-hexen-1-al (2HX) showed color absorption at 608 nm in distilled water after reaction with an acidified vanillin solution. Absorbance also increased significantly when 2HX was added to a series of linalool solutions; ≈2.5 mg 2HX per liter of a 1-mg·liter–1 linalool solution increased the absorbance by >10%. Adding 2.5 mg 2HX per kilogram of `Gewürztraminer' berry homogenate significantly increased apparent free volatile terpene (FVT) concentrations to 121% of unadulterated control treatments but did not affect potentially volatile terpenes (PVT). Adding 2HX also increased apparent FVT concentration in `Perlette' and `Flame Seedless'. Both neutral-flavored table grape cultivars contained some FVT and PVT as a consequence of their muscat ancestries. FVT and PVT quantitation by colorimetric methods may be subject to significant error if the concentration of 2HX and other unsaturated C6 compounds in grape berries or must are >5 mg·liter–1. However, low concentrations of unsaturated C6 compounds (<80 μg·liter–1) in British Columbia wines suggest that there is a low probability of significant interference with this method.

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Andrew G. Reynolds and Andrew P. Naylor

Glasshouse-grown `Pinot noir' and `Riesling' grapevines (Vitis vinifera L.) were subjected to one of four water stress durations [no water deficit (control); and water deficits imposed postbloom, lag phase, and veraison] in combination with three soil water-holding capacities (0%, 26%, and 52% gravel, by volume). Vines subjected to increasing water stress duration had less cumulative lateral shoot length and lower shoot count, leaf size, and berry weights than those not stressed. Soluble solids concentration (SSC) during maturation and pH at harvest also increased with increasing water stress duration, but titratable acidity was not affected. Transpiration and stomatal conductance also were reduced with increased water stress duration, but soil water increased, reflecting the larger leaf surface on vines with veraison-imposed deficits. Reducing water-holding capacity (by increasing the percentage of gravel in the soil) tended to increase berry weight and SSC but reduced lateral shoot growth. The 52% gravel treatments increased transpiration rate and stomatal conductance for `Riesling' but reduced them slightly in `Pinot noir'. Percentage of soil moisture was reduced linearly with reduced water-holding capacity. These results indicate that early irrigation deficits may advance fruit maturity of wine grapes with concomitant reductions in vegetative growth. Differential responses of these cultivars to soil water-holding capacity also should help to identify suitable wine grape cultivars as the wine grape industry expands into areas with low water-holding capacity soils.

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Andrew G. Reynolds and Douglas A. Wardle

Nine wine grape cultivars [`Chardonnay', `Gewurztraminer', `Ortega', `Riesling', `De Chaunac', `Marechal Foch', `Okanagan Riesling', `Seyval blanc', and Verdelet'], own rooted or grafted to four rootstocks [`Couderc 3309' (Vitis riparia × V. rupestris); `Kober 5BB' (5BB), `Teleki 5C', and `Selektion Oppenheim 4' (SO4) (V. riparia × V. berlandieri)] were planted into a randomized complete block experiment in 1985. Data were collected on yield components, weight of cane prunings (vine size), and fruit composition between 1989 and 1996. Yield per vine, clusters per vine, cluster weight, and berry weight were not affected by rootstock, but SO4 tended to produce lowest berries per cluster. Lowest vine size was associated with 5BB and own-rooted vines were usually largest; 5BB was also associated with highest crop load (yield to vine size ratio). Own-rooted vines tended to produce berries with lowest percentage soluble solids (%SS) while 5BB led to highest %SS. Titratable acidity was not strongly affected and pH differences between rootstocks were very small. These data suggest that rootstocks may not provide significant advantage over own-rooted vines under conditions found in the arid regions of the Pacific northwestern U.S. and British Columbia.

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Andrew G. Reynolds and Christiane de Savigny

Vestigial seeds of `Sovereign Coronation' table grapes frequently form partial seedcoats that are perceptible during consumption. This problem was addressed through cane/cordon girdling and gibberellic acid (GA3) sprays. `Sovereign Coronation' vines were subjected to one of five treatments [untreated control; cane/cordon girdled; 15 ppm GA3 at bloom (GA1); GA1 + 40 ppm GA3 14 days later (GA2); GA2 + 40 ppm GA3 14 days later]. GA3 had no effect on yield or clusters per vine, but postbloom GA3 treatments increased cluster and berry weights and reduced berries per cluster. Fruit maturity was not consistently affected by the treatments, although slight increases in °Brix and pH and decreases in titratable acidity (TA) were associated with postbloom GA3 treatments. Use of postbloom GA3 applications reduced the number and weight of vestigial seeds with developed seedcoats, and reduced the number and weight of undeveloped seeds as well in 2 of 3 years. Girdling increased cluster and berry weights, decreased °Brix and TA, and increased pH. Transpiration rate of leaves on girdled vines was also higher than control vines on one sampling date. Data suggest that use of bloom and postbloom GA3 applications to `Sovereign Coronation' may reduce the formation of perceptible vestigial seeds and thus improve the marketability of this cultivar.

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Andrew G. Reynolds, Margaret Cliff, Douglas A. Wardle and Marjorie King

Eighty-five cultivars, selections and clones from European winegrape (Vitis spp.) breeding and selection programs were evaluated between 1993 and 1995 in a randomized complete-block experiment. These included Vitis vinifera clones from France as well as Freiburg, Geisenheim, and Weinsberg, Germany. Small yield and fruit composition differences were found amongst the 'Chardonnay' clones. The standard Prosser clone produced wines with highest earthy aroma and acidity and with lowest perfumy aroma, body and finish; Dijon clones 76 and 96 were most perfumy and least vegetal. `Pinot noir' clones also differed somewhat in terms of yield and fruit composition; `Samtröt', `Gamay Beaujolais', and clone Q1342-01 were amongst the most highly colored clones. These clones also tended to have the most intense berry and currant aromas as well as berry, cherry, and currant flavors. These aforementioned clones appear to be highly adaptable to viticultural regions where low heat units during fruit maturation presently limit industry growth.

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Andrew G. Reynolds, Margaret Cliff, Douglas A. Wardle and Marjorie King

Eighty-five cultivars, selections and clones of winegrapes (Vitis) from European breeding and selection programs were evaluated between 1993–95 in a randomized completeblock experiment. These included selections from Alzey, Freiburg, Geilweilerhof, Geisenheim, Weinsberg, and Würzburg (Germany); Hungary; and the former USSR. Vines were grown under an organic management regime that included sodium silicate sprays for powdery mildew (Uncinula necator) control and oil + detergent for insect control but with little to no nitrogen or other nutritional inputs. The Weinsberg cultivars Heroldrebe and Helfensteiner showed promise viticulturally and sensorially as alternatives to `Pinot noir'. Cultivars from Geisenheim (`Gm 7117-10' and `Gm 7117-26') and Würzburg (`Cantaro' and `Fontanara') appeared promising as `Riesling' alternatives; many displayed similar sensory characteristics to `Riesling', along with reasonable viticultural performance. Cultivars selected at Alzey (`Faberrebe'), Freiburg (`Nobling'), and Weinsberg (`Holder') displayed sensory characteristics superior to the standard cultivar Müller-Thurgau, with very intense muscat, pear, fig, and spicy aromas and flavors. Several muscat-flavored Hungarian white wine cultivars appeared to be superior viticulturally and sensorially to the standard `Csabagyongye'; these included `Kozma Palne Muscotaly', `Zefir', and `Zengo'. Miscellaneous red wine cultivars that showed promise included Geilweilerhof cultivar Regent, and Hungarian selections Kozma 55 and Kozma 525. Vine yields decreased substantially in the 3-year evaluation period, primarily due to lack of nitrogen. Many of these cultivars appeared to be highly adaptable to viticultural regions where cold winters and low heat units during fruit maturation presently restrict cultivar choices.

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Andrew G. Reynolds, Douglas A. Wardle and Marjorie Dever

Vitis vinifera L. cultivars Müller-Thurgau, Muscat Ottonel, Gewürztraminer, and Kerner were studied for 1 year to document changes in fruit terpene levels from berry stage to free-run and press-juice stages. Substantial amounts of free volatile terpenes (FVTs) and potentially volatile terpenes (PVTs) were lost between berry and juice stages. PVTs were higher in press juices of `Gewürztraminer' and `Muscat Ottonel' than in free-run juices. In another experiment, juices from `Miiller-Thurgau', `Muscat Ottonel', `Kerner', `Optima', `Pearl of Csaba', and `Siegerrebe', harvested 10 to 20 days after a designated initial harvest date, contained higher FVTs and PVTs than initially. A third experiment with `Kerner', `Müller-Thurgau', `Optima', and `Siegerrebe' found highest FVTs and PVTs in juices from grapes subjected to skin contact compared with grapes crushed and immediately pressed. Sensory evaluation showed aroma differences between wines from free-run and press juices of `Miiller-Thurgau' and `Muscat Ottonel', aroma and flavor differences due to harvest date for all cultivars except `Pearl of Csaba', and aroma and flavor differences due to skin contact for `Siegerrebe'.

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Andrew G. Reynolds, Amal Ehtaiwesh and Christiane de Savigny

Several irrigation treatments were evaluated on ‘Sovereign Coronation’ (Vitis labruscana) table grapes at two vineyard sites in Ontario, Canada in 2003 to 2005 to assess the usefulness of the Food and Agriculture Organization of the United Nations Penman-Monteith equation for predicting vine irrigation needs. Data (relative humidity, wind speed, solar radiation, and temperature) for calculating reference evapotranspiration (ETo) were downloaded from the Ontario Weather Network. The five irrigation treatments were nonirrigated control plus four based on combinations of one of two ETo values [100% (ET100) or 150% (ET150)] and two crop coefficients [Kc (fixed at 0.75 or 0.50.8 based upon increasing canopy volume)] used to calculate the required irrigation water volume. Transpiration (Ts), leaf water potential (ψ), and soil moisture data were collected in all three seasons. Yield components data were collected and berries were analyzed for soluble solids, pH, titratable acidity (TA), anthocyanins, methyl anthranilate (MA), and total volatile esters (TVE). Irrigation typically increased Ts rate and soil moisture; the nonirrigated treatment showed consistently lower Ts and soil moisture over the three seasons. Irrigation also increased leaf ψ, which was lower throughout the three seasons for nonirrigated vines. Irrigation additionally increased yield and its various components (clusters per vine, cluster weight, and berries per cluster) in 2005. Berry weights were higher for irrigated treatments at both sites, and were consistently the main variable leading to yield increases. Soluble solids was highest for the Kc = 0.75 treatments. pH, TA, anthocyanins, and phenols were highest in nonirrigated treatments in 2003 and 2004, but were highest in irrigated treatments in 2005. MA and TVE were highest in the ET150 treatments. The use of irrigation was effective in reducing water stress and for improving yield and fruit composition of ‘Sovereign Coronation’ table grapes in the Niagara region of Ontario. The ET150 treatments were particularly beneficial. Soil and vine water status measurements indicated that irrigation was required for Summer 2003 and 2005 due to dry conditions.

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Andrew G. Reynolds, Douglas A. Wardle, Brian Drought and Robert Cantwell

Own-rooted, glasshouse-grown `Chardonnay' vines (Vitis vinifera L.) were planted in a sand medium to which was added one of five levels of granular Gro-Mate (GM), a commercial humate (0, 8, 16, 32, 64 g/pot; 0 to 35 g a.i./pot). Two other treatments consisted of weekly (1× W) or twice-weekly (2× W) applications of liquid GM, whose cumulative addition over the 28 weeks of the experiment totaled 6.7 and 13.4 g a.i., respectively. Shoot length responded to increasing level of GM in a predominantly cubic fashion, with 32 g/pot resulting in the longest shoots. Fresh and dry weights of leaves, shoots, and roots, as well as leaf count and area, exhibited increasing linear or quadratic trends in response to increased level of granular GM. GM increased soil organic matter, K, Ca, Mg, Fe, Mn, Cu, Na, and S and also increased petiole Fe and lamina P, K, and Fe. Liquid treatment resulted in lower soil pH, organic matter, bulk density, and Fe and higher soil conductivity, NO3, P, K, Mg, Cu, Zn, Na, and S than the granular treatments, as well as higher petiole and lamina N and K, lower petiole and lamina P, and lower petiole Zn. Compared to the 1× W treatment, the 2× W produced lower soil bulk density and higher P, lower lamina K, Mn, and Fe; lower petiole Mn; and higher petiole Cu. Plant tissues contained extremely high levels of Mn irrespective of treatment, whereas liquid treatments resulted in high soil NO3 levels. Although liquid GM cannot be recommended for young grapevines under an application regime such as described here, preplant applications of granular GM may have potential for improving growth of young vines in coarse-textured soils. High granular or excessive liquid applications may result in leaf necrosis and retarded growth.

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Andrew G. Reynolds, A.C. Cottrell, D.A. Wardle and A.P. Gaunce

`Okanagan Riesling' (Vitis spp. parentage unknown) vine trunks treated in 1984 with three levels of NM (0, 10,000, and 20,000 mg·liter-1) and three levels of paclobutrazol (PB; 0, 250, and 500 mg·liter-1, in white latex paint were subjected to a reapplication in June 1987 at the same rates of NAA and at 0, 1000, and 2000 mg PB/liter. Linear reductions in suckers per vine were observed with increasing NAA concentration but not PB. Yield and clusters per vine were reduced by PB in the season following retreatment (1988), while berry weight was increased by NAA in 1987. Titratable acidity was increased by NAA in 1988, and pH was highest that season with PB at 1000 mg·liter-1 . No PB was detected in fruit tissue in 1987, but NAA levels of 2.4 and 2.0 μg·kg-1 were detected in clusters sampled from the 10,000- and 20,000-mg·liter -1 treatments, respectively. Chemical names used: l-naphthaleneacetic acid (NAA); β-1[(4-chlorophenyl)methy]-α-1 (l,l-dimethylethyl)-1H-l,2,4-triazole-l-ethanol (paclobutrazol).