American Journal of Enology and Viticulture

Published by American Society for Enology and Viticulture
Online ISSN: 0002-9254
Publications
Article
Taste phenotypes have long been studied in relation to alcohol intake, dependence, and family history, with contradictory findings. However, on balance - with appropriate caveats about populations tested, outcomes measured and psychophysical methods used - an association between variation in taste responsiveness and some alcohol behaviors is supported. Recent work suggests super-tasting (operationalized via propylthiouracil (PROP) bitterness) not only associates with heightened response but also with more acute discrimination between stimuli. Here, we explore relationships between food and beverage adventurousness and taste phenotype. A convenience sample of wine drinkers (n=330) were recruited in Ontario and phenotyped for PROP bitterness via filter paper disk. They also filled out a short questionnaire regarding willingness to try new foods, alcoholic beverages and wines as well as level of wine involvement, which was used to classify them as a wine expert (n=110) or wine consumer (n=220). In univariate logisitic models, food adventurousness predicted trying new wines and beverages but not expertise. Likewise, wine expertise predicted willingness to try new wines and beverages but not foods. In separate multivariate logistic models, willingness to try new wines and beverages was predicted by expertise and food adventurousness but not PROP. However, mean PROP bitterness was higher among wine experts than wine consumers, and the conditional distribution functions differed between experts and consumers. In contrast, PROP means and distributions did not differ with food adventurousness. These data suggest individuals may self-select for specific professions based on sensory ability (i.e., an active gene-environment correlation) but phenotype does not explain willingness to try new stimuli.
 
Article
A bibliometric analysis of wine publications and citations by country and over time related a country's scientific performance in wine research to its position in the global wine market as a producer, a consumer, or both. Results highlight the extent to which scientific positions can help to explain the emergence of some countries as new participants in the wine industry and established countries as old participants defending their positions. We also examined the extent to which the scientific wine community is in itself becoming increasingly more global through international co-publications. Results suggest that geographical trends in the scientific wine community are only partly related to the shifts in globalization patterns in the wine industry.
 
Article
The National Clonal Germplasm Repository (NCGR) in Davis, California (CA) maintains the United States collection of warm-climate grapes in a field genebank in Winters, CA. This collection includes numerous accessions that are highly susceptible to Pierce's disease (PD) as well as many PD-tolerant accessions that are native to the southeastern United States. If the glassy-winged sharpshooter became established in the Winters area, then reservoirs of the PD causal agent Xylella fastidiosa (Xf) within the collection would provide abundant inoculum for the rapid spread of Xf throughout the genebank. Therefore, PCR screening for Xf was conducted using a primer pair that is genome sequence specific to Xf and is reported to provide a high degree of sensitivity and specificity to all Xf strains that have been tested. Basal leaf petioles were collected from 60 different accessions in the NCGR representing a broad cross section of taxa and periods of time since collection in the region where Xf is endemic. Only Chardonnay previously inoculated was found positive for presence of Xf. It is concluded that NCGR grape accessions collected as budwood in the southeastern United States, where Xf and PD are endemic, are not a significant reservoir of Xf. There appears to be no reason for removing these vines if GWSS populations become established in the area surrounding the genebank.
 
Article
The presence of local vines in the Tuscia area (Latium region, Italy) was documented by historical sources. Ampelographic and molecular characterization (35 morphological descriptors and 16 microsatellite loci) was carried out on accessions belonging to the most frequently mentioned local vines. SSR markers have enabled us to distinguish cases of local synonymy and microsatellite profiles have permitted comparison with previously reported profiles indicating synonymy and divergence with vines in other collections. Ampelographic traits showed that some accessions of the same genotype differ in minor characteristics that can have a role in clonal evaluation.
 
Article
Grape ripening is thought to be ethylene independent. However, Cabernet Sauvignon berries that were treated with 1-methylcyclopropene (1-MCP), a specific inhibitor of ethylene receptors, accumulated less sucrose over the following three weeks than did controls. This was associated with a decreased RNA accumulation of two sucrose transporters (SUC11 and SUC12), whose expression is triggered at the veraison stage when grape berries start to accumulate sugars. These observations were performed over two consecutive years. This preliminary study suggests that the role of ethylene in grape ripening needs to be reconsidered and that it could be related to sugar accumulation.
 
Article
Thesis (M.S. in Food Science)--University of California, Davis, Sept. 1959. Includes bibliographical references (leaves 54-57).
 
Dates and duration of temperature control treatments applied to Merlot clusters.
Relationship between temperature from veraison until harvest and proportion of total anthocyanin as (A) delphinidin, (B) cyanidin, (C) petunidin, and (D) peonidin-based anthocyanins in berry skins from Merlot clusters in full sun. Thermal time is expressed in degree days (DD; base 10°C). MeanT refers to mean berry temperature from the first visible sign of veraison to harvest. Description of treatments in Table 2. Regressions based on data over three growing seasons (n = 55).
Berry mass, percent soluble solids (%SS), titratable acidity (TA), pH, total skin anthocyanins (TSA), and total flavonol-glycosides of Merlot berries from three growing seasons.
-solar radiation regimens applied to clusters of Merlot and summary of actual temperatures achieved among treat- ments between veraison and harvest, averaged across three growing seasons.
values of individual and total flavonol-glycoside concentrations in berry skins from Merlot across three seasons for 10 temperature-solar radiation regimens.
Article
Using a forced convection system, temperatures of Merlot grape clusters were monitored and con- trolled between veraison and harvest to produce a dynamic range of berry temperatures under field conditions in both sun-exposed and shaded fruit. Ten combinations of temperature and solar radiation exposure were used to quantify effects on phenolic profiles (anthocyanins and flavonol-glycosides) and on total concentrations of skin anthocyanin (TSA) in the fruit at commercial maturity. Exposure of berries to high temperature extremes for relatively short periods during ripening appears to alter the partitioning of anthocyanins between acylated and nonacylated forms and between dihydroxylated and trihydroxylated branches of the anthocyanin biosynthetic pathway. Specifically, among flavonol-glycosides, quercetin 3-glucoside increased with exposure to solar radia- tion. Low incident solar radiation alone appeared not to compromise total anthocyanin accumulation; rather, a combination of low light and high berry temperatures decreased TSA. Regardless of exposure to solar radiation, higher berry temperatures led to a higher concentration and a higher proportion of TSA comprised by malvidin- based anthocyanins, driven primarily by increases in the acylated derivatives. Under shade alone and under high temperature extremes in sunlit and shaded fruit, acylated anthocyanins represented a larger proportion of TSA than did nonacylated anthocyanins. At berry temperatures equivalent to those of shaded fruit, exposure to solar radiation decreased the proportion of TSA comprised by acylated forms of the five base anthocyanins and increased the proportion of TSA comprised by dihydroxylated anthocyanins. Results indicate a complex combined effect of solar radiation and berry temperature on anthocyanin composition, synergistic at moderate berry temperatures and potentially antagonistic at high temperature extremes.
 
Article
Seven cover-crop treatments were compared in two north Willamette Valley Pinot noir vineyards over two years to test if alleyway cover crops that are mowed in spring and summer compete with grapevines for water or nutrients. Five different cover-crop mixtures were compared to a clean-cultivated control and resident vegetation treatments in 2004 and 2005. Treatments were evaluated for biomass production, quantity of nitrogen (N) contributed to the vineyard floor, weed suppression, and effect on soil water content. Vine responses to the different floor-management strategies included measures of shoot growth, water and nutrient status, yield, and juice quality. Three treatments were evaluated for their effect on fine roots and colonization by arbuscular mycorrhizal fungi (AMF). Cover crops influenced soil moisture in a different manner at each site, although the lowest soil moisture was consistently found in the perennial grass and clover mixture. Cover-crop treatments had an impact on grapevine N status at one vineyard, altering leaf blade N concentrations at bloom and juice N concentrations at harvest, although different treatments did not alter N status consistently over time. Cover crops did not alter shoot growth, pruning mass, leaf water potential, fine root density, or colonization of roots by AMF and did not affect yield, cluster weights, juice soluble solids, pH, or titratable acidity. Results showed that alleyway cover crops managed by spring and summer mowing do not have consistent effects on grapevines in western Oregon vineyards and suggest that little competition occurs between cover crops and vines in the mixtures evaluated. Further examination of cover crops composed primarily of clovers or of perennial grasses is warranted.
 
Article
Vineyard replant disorder is a disease of unknown etiology, currently controlled by methyl bromide fumigation. While not all the components of the disease are known, plant-parasitic nematode densities are of- ten high in vineyard replant soils. Alternatives to the broadly effective general biocide, methyl bromide, are needed for vineyards replanted after January 2005, when import and manufacture of methyl bromide was banned ex- cept for exempted quarantine uses and approved critical uses. Two field trials were conducted in vineyards that had been planted to own-rooted Thompson Seedless grapes for 70 to 85 years and were known to support popu- lations of plant-parasitic nematodes. In a randomized block design with five or six replicates per trial, shank- injected and/or drip-applied propargyl bromide (>207 kg ha -1 ), iodomethane + chloropicrin (50:50, >269 kg ha -1 drip-applied), and 1,3-dichloropropene + chloropicrin (InLine, 468 L ha -1 ) provided control of plant-parasitic nematodes throughout the first growing season similar to control achieved with methyl bromide (507 kg ha-1). Chloropicrin (448 kg ha-1) provided less nematode control than methyl bromide, but significantly greater con- trol than untreated. An experimental drip formulation of sodium azide (Agrizide, 336 kg ha -1 ) was insufficient to control nematodes under vineyard replant conditions. Although vine growth in the treated plots was gener- ally greater than in the untreated plots, growth was greater with methyl bromide than with the alternative chemicals. Alternatives to methyl bromide for nematode control in sandy loam soils were documented, but acceptable al- ternatives for the management of the complex vineyard replant disorder are more elusive.
 
Article
A new method of measuring the total phenolic compounds in wine and tea is proposed. The method is based on the fact that the decreased amount of H2O2 caused by the action of peroxidase is proportional to the oxidized amount of phenolic compounds in the solution. Decrease in H2O2 was sensitively detected with a semipermeable-membrane-covered, horseradish-peroxidase-entrapped, and ferrocene-embedded carbon paste electrode. This electrode allows the detection of (+)-catechin down to 0.3 μM and the response is linear up to 15 μM. The content of total phenolic compounds in wine and tea samples determined by the present method agrees well with results obtained by the Folin-Ciocalteu method. Advantages of the proposed method over the Folin-Ciocalteu method include shorter detection time, smaller sample volume, one order of magnitude higher sensitivity, lesser degree of interference from coexisting SO2 and glucose, and applicability to colored, turbid, or colloidal samples. The method is not influenced by the oxygen level in samples. Samples require pretreatment if ascorbic acid is present.
 
Article
In a plant breeding program, an accurate understanding of pedigrees provides useful guidance for future hybridizations. However, plant breeder records occasionally contain errors which may mislead future breeding efforts, and there is considerable value in independently testing reported pedigrees. In this project, SSR markers were used to confirm or correct pedigrees for grape varieties from the Cornell breeding program and a few key varieties used as parents. As expected, most (20 of 24) reported pedigrees were confirmed. Recognizing a heritable null allele from Ontario, at VVMD25, was necessary for parent progeny analysis of several varieties. Suffolk Red and Glenora were shown to be progeny of Black Kishmish and not Black Monukka. The advanced selection NY63.0970.07 is a hybrid of Pinot noir, not Gamay, x Chancellor. Vignoles (Ravat 51) is not descended from the reported parentage of Seibel 6905 x Pinot noir.
 
Article
Pierce's disease (PD), caused by the bacterium Xylella fastidiosa, is an important disease of grapevines in California, across the southern United States, and into South America. In regions where disease pressure is high, the cultivation of Vitis vinifera cultivars is difficult or impossible. This study reports on the introgression of PD resistance into elite wine, table, and raisin grape genetic backgrounds and on the reliability of PCR-based marker-assisted selection (MAS) to accelerate the breeding of PD-resistant grapes. This work documents the introgression of PD resistance from a homozygous resistant form of V. arizonica, b43-17. A total of 4,321 seedlings from 83 different crosses of resistant selections and high-quality V. vinifera cultivars from the F1 and first and second modified backcross generations (mBC1 and mBC2) were screened with two to three flanking microsatellite markers (VVIP26, ctg1026876 and VMC2a5) in the early spring 2006 and 2007. The alleles linked to resistance were unique in size and were not shared by susceptible V. vinifera selections. Based on the presence of unique resistant alleles, 1,683 seedlings from wine, table, and raisin grape background were selected. The distinctiveness of these resistant alleles allows the use of MAS to optimize the breeding of PD-resistant grape cultivars.
 
Article
Rachis, raisins, rotten, and sun-burnt berries were removed from hand-harvested Chardonnay by automated color sorting. Rejected material comprised 4% (w/w) of the crop. Wine was made from sorted and unsorted fruit and was subjected to chemical and sensory analysis. Chemical analysis found that the sorted wine had a higher total phenolic level, pH, and residual sugar content. Sensory analysis showed sorted wine significantly differed in two attributes: higher tropical fruit aroma and higher sweetness. The two wines could not be strongly differentiated in other sensory characteristics, showing great similarity in palate attributes.
 
Article
In-line dosing with bentonite provides an alternative to traditional batch fining for the removal of haze-forming proteins from white wine. When combined with centrifugation, in-line dosing can reduce wine losses and quality downgrades. In this production-scale study, Chardonnay and Semillon-Chardonnay wines were fined with three commercially available bentonites. A contact time of approximately 3 minutes was adequate for adsorption of the haze-forming proteins. No significant sensory difference was observed in the wines treated by in-line dosing and by batch fining. However, some carryover of bentonite into the centrifuge product was observed. This carryover was substantially lower when using a sodium-calcium bentonite compared with a sodium bentonite. The carryover was also significantly reduced by operating the centrifuge at lower flow rates. Copyright © 2007 by the American Society for Enology and Viticulture.
 
Article
Anthocyanin and phenolic profiles of berry skins from Vitis vinifera cv. Merlot in the Yakima Valley of Washington were influenced by sun exposure and temperature in 1999 and 2000. Growing degree days (base 10°C) accumulated between veraison and harvest were lower in 2000 than in 1999. Total skin monomeric anthocyanin (TSMA) concentrations were higher in 2000 than in 1999 in any given treatment. Berry temperature was increased as much as 13°C above ambient and shaded cluster temperatures when clusters were exposed to sunlight, regardless of aspect for north-south oriented rows. However, maximum fruit temperatures were higher for clusters on the west side of the canopy because ambient temperatures were higher after 1200 hr. Temperatures of west-exposed clusters at times exceeded 40°C. East-exposed clusters had higher TSMA concentrations than west-exposed or shaded clusters. To separate light and temperature effects, west-exposed clusters were cooled to the temperature of shaded clusters and shaded clusters were heated to the temperature of west-exposed clusters. Exposure to sunlight increased TSMA concentrations regardless of temperature in both years. In 1999 and 2000, cooling sun-exposed clusters increased TSMA concentrations. Heating shaded clusters decreased TSMA concentrations in 1999, but had no effect during the cooler ripening period of 2000. Ultraviolet (UV) light barriers did not influence either cluster temperature or TSMA concentrations. Decreased TSMA concentrations in berry skins from west-exposed clusters were due to temperature and not to UV radiation. Exposure to solar radiation increased concentrations of the 3-glycosides of quercetin, kaempferol, and myricetin. In 2000, sun-exposed clusters, regardless of aspect, had almost 10 times greater concentrations of total flavonols than shaded clusters. UV-light barriers significantly reduced individual and total flavonol concentrations, while temperature had little to no effect on their concentrations.
 
Article
Quiescent infections play key roles in Botrytis cinerea pathogenesis and in the management of Botrytis bunch rot on Vitis spp. An improved understanding of the biology of quiescence and identification of resistant germplasm could result in improved disease management. In 2004 and 2005, two methods were applied to monitor quiescence and activation of natural B. cinerea infections on 32 genotypes of Vitis spp. and interspecific hybrids. In addition to the standard assay for early detection of B. cinerea, based on tissue freezing and incubation, a real-time quantitative PCR (qPCR) assay was developed and tested. Based on Taqman chemistry, this qPCR assay quantified as little as 3.2 pg of B. cinerea DNA accurately, with a detection limit of 100 fg, and did not amplify grape DNA. The qPCR and freezing assays detected infection levels of B. cinerea in both 2004 and 2005 appropriate to the actual disease severity (22.5% and 1.0% bunch rot, respectively). Grape genotypes varied in their resistance to infection, degree of colonization, and severity of disease. qPCR was not as effective as the freezing assay for detecting infection at early stages of development but was able to quantify fungal colonization, resulting in a new capability for monitoring B. cinerea pathogenesis over time. The combined ability of the two assays to detect B. cinerea early in berry development and monitor colonization provides a resource for informing disease management decisions and for identifying mechanisms of disease resistance.
 
Predictor variables measured on grapevine leaves for the creation of allometric statistical models of leaf area on Cabernet Sauvignon and Shiraz cultivars. All the predictor variables were drawn from the literature. For full description of the various lengths, see text.
Article
The planimetric area of grapevine leaf blades (LA) is required as input data in many grapevine growth models and quantitative studies of the soil/plant/atmosphere continuum. A subset of 300 scanned grapevine leaves was used to identify and compare allometric statistical models predicting the leaf area of grapevines (cultivars Cabernet Sauvignon and Shiraz). The mean absolute error (MAE), root mean square error (RMSE), and Δ (RMSE-MAE) were used as discriminatory criteria. Six families of models drawn from the literature were compared with stepwise regression using up to six possible predictor variables. Each family was fitted to each cultivar for three vineyard sites. Generic models were computed by aggregating the data across sites and cultivars. The Queensland (stepwise regressions) family performed best, closely followed by Elsner2 and Montero. The MAE of some generic models was at times less than that of their components because of the influence of sites and/or cultivars. Site-and cultivar-specific stepwise regressions are generally the most accurate methodology for estimating leaf surface area. Simple models were generally less accurate than models integrating several predictor variables.
 
Article
Members of 10 fungal genera were isolated from diseased grape berries and stems collected in a local vineyard. These fungi were identified as Alternaria sp., Aspergillus japonicus, Cladosporium cladosporioides, Colletotrichum sp., Curvularia brachyspora, Epicoccum purpurascens, Greeneria uvicola, Nigrospora sphaerica, Trichoderma sp., Penicillium sclerotiorum and P. thomii. CAY-1, a fungicidal saponin in cayenne pepper (Capsicum frutescens) was significantly (p ≤ 0.05) lethal to the germinating (incubated 8 hr) but not the nongerminated (0 hr incubation) conidia of all the fungi except Alternaria and E. purpurascens at concentrations greater than 7.5 μM. CAY-1 was ineffective against the conidia of all the isolated fungi incubated 24 hr prior to mixing with the saponin. Results show that, in vitro, CAY-1 is lethal to these fungi only during their early germination cycle. Copyright © 2008 by the American Society for Enology and Viticulture (to the extent allowed for U.S. federal government employed authors). All rights reserved.
 
Article
Mycorrhizal colonization of grafted grapevines was studied during early establishment of an experimental rootstock vineyard to determine rootstock variability forming functional mycorrhizas. Roots of 10 different rootstocks were examined for the presence of arbuscular mycorrhizal (AM) fungi at the end of the second growing season (1998), and at the time of veraison (onset of ripening) of the third (1999) and fourth (2000) growing seasons. The fine root length density (primary roots with intact cortex) increased in 6 of 10 rootstocks over time. Only one rootstock, Riparia Gloire, showed a marked decrease in fine root length density in 2000, when vines carried their first significant fruit crop. AM colonization was generally above 60% of fine root length for all rootstocks, although significant differences due to rootstock and time of sampling were evident. Rootstocks imparting greater vigor to the scion, particularly Ruggeri 140, Kober 5BB, and SO-4, had consistently higher levels of root colonization by AM fungi. The proportion of roots containing arbuscules at veraison declined from 1999 to 2000 in those rootstocks carrying the highest crop loads. While AM colonization of different rootstocks was positively correlated to yield, the proportion of roots with arbuscules was negatively correlated to yield in 2000. Results of this study show that small differences in the ability to form mycorrhizas exist among rootstocks, but other factors, including crop load and soil moisture, have a large influence on root colonization by AM fungi.
 
Representation of the first two preference dimensions for the 12 selected wines by 120 consumers: correlations of the wine scores ( A ) and of the individual consumer liking scores ( B ) with the preference dimensions. Dots (•) represent individual consumers from cluster 1 (coded 1) and cluster 2 (coded 2). Vectors point toward the sensory attributes projected on the preference dimensions. C1: vector pointing toward the liking direction of cluster 1. C2: vector pointing toward the liking direction of cluster 2. 
selected for the sensory evaluation. All wines were used for the descriptive analysis; indicated wines were used for the consumer analysis.
Article
The sensory preferences for white wines of three consumer groups selected for their differences in wine consumption habits and attitudes toward wines were investigated. A stepwise screening of the wines was used to ensure an objective selection based solely on perceived sensory characteristics while representing the commercial market. Sensory profiles of the selected wines were then determined by trained sensory descriptive panelists (n = 10). Consumers (n = 120) were recruited, assigned to one of three a priori groups, and evaluated 12 white wines. Internal preference mapping was conducted to explain consumer preference data with wine sensory descriptions and consumer characteristics. Results showed that sensory preferences were not significantly different among a priori consumer groups. Segmentation of individual liking scores revealed two distinct preference segments, with the largest one accounting for 77%. The majority of consumers preferred sweeter and fruitier wines as opposed to oaky and burning wines, independently of their a priori assigned group. Only a few demographics and attitudinal characteristics distinguished the two preference segments; however, they were not related to the initial a priori grouping. The primary dimension explaining consumer preferences for white wines confirmed previous research findings on other wine styles and obtained from various groups of consumers, suggesting that the main preference dimension common to many wine styles was driven by sweet and fruity sensory characteristics as opposed to dry, burning, and oaky attributes.
 
Relationship between square root of leaf area per shoot and (A) shoot basal diameter (df = 1, P > F <0.0001, R 2 = 0.58, y =-2.69 + 6.54x), (B) the log of number of leaves per shoot (df = 1, P > F <0.0001, R 2 = 0.85, y =-13.27 + 19.77x), and (C) the square root of shoot length (df = 1, P > F <0.0001, R 2 = 0.90, y =-3.14 + 4.27x), 2002-2006. The solid line reaching the right edge of each panel represents the linear fit to these data across all years. Broken lines represent linear fits for each year. Insets display results from the test for heterogeneity of slope between years. Bars represent relative magnitude of the slopes, and slopes sharing a letter are not significantly different.
Mean (±SE) square root of leaf area per shoot from 20022006 by (A) calendar day and (B) degree days (start 1 Jan with 10°C lower threshold and no upper threshold).
Article
Three potential variables, shoot basal diameter, leaf count per shoot, and shoot length, were examined as potential rapid, nondestructive methods for estimating leaf area per shoot, a frequent component of estimates of leaf area per vine. The metrics were recorded in large field-grown vines over five years. Shoot basal diameter, the most rapid method, was not a good predictor of leaf area per shoot. After transformation, shoot length and leaf count per shoot had relatively tight linear relationships with the square root of leaf area per shoot (R2 = 0.90 and R2 = 0.85, respectively). Some of the variation in the relationships due to between-year and within-season variability can be reduced by expressing the relationships as a function of thermal time. Furthermore, nonlinear models can be fit to the ratio of leaf area per shoot to the rapidly obtained metrics. Using this ratio approach accounts for the dynamics of canopy development and should increase the accuracy of leaf area estimates during early-season rapid shoot growth. Early in the season the length and count measurements can be made at ∼0.5 min per shoot, but as the canopy develops and shoots intertwine, the sampling rate progressively slows to ∼2.5 min per shoot. Copyright © 2007 by the American Society for Enology and Viticulture. All rights reserved.
 
Daily air temperatures (A), total solar radiation (B), precipitation (C), and mean wind velocity (D) recorded by the Public Agricultural Weather System weather unit at WSU-IAREC, Prosser, WA during the 1998 growing season.
continued
Daily air temperatures (A), total solar radiation (B), precipitation (C), and mean wind velocity (D) recorded by the Public Agricultural Weather System weather unit at Alderdale, WA during the 1999 growing season.
Biomass of cover crops and weeds in commercial vineyard plots, 1999. Canada mix consists of Fairway crested wheatgrass, pubescent wheatgrass, and perennial ryegrass. Fescue mix consists of tall, hard, and sheep fescues. Control plots consist of resident vegetation.
Cover crops selected from large evaluation trial in 1998. Entries commercially available were planted in a commercial vineyard (Alderridge Vineyard, Corus Brands, Inc.), Alderdale, WA, 1999.
Article
Numerous cover crops for orchards and vineyards have been evaluated, but many selections do not necessarily perform well in the cold, arid environment of the inland Northwest. A cover crop between vine rows can mitigate wind erosion and subsequent damage to young vines. However, low rainfall, gusty winds, and sandy soils that cause significant wind erosion problems can exacerbate cover crop establishment, and cold winters can limit cover crop survival. During 1998, 175 plant accessions were screened for performance as vineyard cover crops at Prosser, Washington. Assessed attributes included percent emergence, percent vegetative cover, stand duration, and plant height. Based on that assessment, seven domestic selections and four foreign Medicago species (medics) were identified for additional evaluation in a research trial in 1999. Additionally, seven accessions and two mixes of species that met the growth criteria and had commercial availability were evaluated in a commercial, drip-irrigated vineyard near Prosser in 1999. Vine water potential and soil moisture were determined in addition to the identical growth criteria from the 1998 study. Cover crop treatments did not lead to detectable water stress in the vines (midday y = -0.84 to -1.30 MPa). However, dry soil between vine rows due to precision drip irrigation inhibited germination and establishment of legumes; therefore, grasses had better emergence rates. Of the mixed species, a grass mix (Canada) composed of crested wheatgrass (Agropyron cristatum L.), pubescent wheatgrass (Elytrigia intermedia L.), and perennial rye (Lolium perenne L.; 40:40:20), depleted soil water the least and showed the least effect on vine water potential. Early season weeds were suppressed by most cover crop species; however, season-long suppression of weed growth was observed only for the Canada mix and crested wheatgrass cv. Fairway.
 
Article
The genetic relationships within a group of ancient grapevine varieties (Vitis vinifera L.) cultivated in a limited area in the Northwest of Spain (Galicia) and the relationships of these varieties with foreign ancient germplasm cultivated in different regions of Spain, France, and Germany were surveyed using RAPD markers. The intralaboratory RAPD reproducibility has been quantified. This study proved that, eliminating weak bands and bands over 1600 bp, the RAPD markers are useful for most intralaboratory applications, and it is not critical to repeat amplifications to obtain coherent studies of genetic relationships. Twenty-nine primers were selected and they produced 260 clear and reproducible RAPD bands in the 16 grapevine varieties studied. Genetic relationships were established by unweighted pair-group method using arithmetic averages (UPGMA) cluster analysis and also by studying RAPD fragments of low frequency. Galician varieties, cultivated since ancient times in this region, were not very similar because some were probably introduced in Galicia from different viticultural areas and have diverse origins. However, five varieties cultivated in a wide area of Spain formed a well defined group significantly separated from the rest. Moreover, varieties that share a supposed common origin and some morphological traits were generally grouped: Airén and Malvar, Pinot noir and Chardonnay, and Albariño and Caíño blanco. Peer reviewed
 
Article
Sap-flow gauges typically are tested by comparing their output to gravimetric measurements of water loss from a potted plant. However, a mature vine of Vitis labrusca cv. Concord, when potted, could not achieve the high rates of sap flow that were observed in similar vines in the field. This limited the range in which the sap-flow gauges could be tested and confidence in their accuracy at high flow rates. Consequently, a laboratory device was constructed to reproduce the high rates of sap flow that were observed in the vineyard on mature grapevines. The device allows gauge testing on a severed vine stem, thereby reproducing the thermal regime of a sap-flow measurement in the field. The design of the device is simple, and its component parts are low cost and easily obtained from commercial sources. The device permits empirical determination of limiting factors in gauge performance as they vary with flow rate. It also permits the establishment of "zero-flow set" or gauge conductance on hydrated stem tissue. Evaluation of the heat-balance method under high rates of sap flow (>1500 g h-1) showed that gauges made from designs that are standard in the literature consistently underestimated gravimetric measurements. Evidence suggests that gauges should be redesigned to accommodate thermal heterogeneity across the vine stem that occurs under high flow.
 
Grape genotypes examined in this study with their 
Article
The xylem-limited bacterium Xylella fastidiosa is the causal agent of Pierce's disease (PD) in grapevines, for which breeding resistant cultivars will be a long-term management strategy that involves the identification and characterization of resistant germplasm. A genetically diverse group of grape species and selections was mechanically inoculated with X. fastidiosa, grown in a greenhouse for 113 days after inoculation, and evaluated for the levels of bacterial concentrations in stem and leaf tissues by quantitative enzyme-linked immunosorbent assay (ELISA). Concentrations of X. fastidiosa were affected by genotype, plant tissue, position on the plant relative to the point of inoculation, and interactions among these factors. Based on estimated concentrations of X. fastidiosa in stem samples at 113 d postinoculation, 9621-67, Muscadinia rotundifolia, Vitis arizonica/candicans, V arizonica/girdiana, V candicans, V girdiana, V nesbittiana, and V shuttleworthii were resistant to PD. In contrast, V vinifera, V aestivalis, 9621-94, and V champinii had very high X. fastidiosa concentrations in stem tissues. Sequential sampling of leaf blades at 34, 77, and 113 d postinoculation revealed different temporal patterns in X. fastidiosa concentrations among the grape genotypes. Estimates of X.fastidiosa concentrations decreased after the first sampling in M. rotundifolia, 9621-67, V girdiana, and V arizonica/candicans but increased in all other genotypes. The characterization of X. fastidiosa concentrations in a broad range of grape genotypes allows for the selection of promising genetic backgrounds capable of greatly limiting the population size and development of X. fastidiosa in stems, a critical trait in the breeding of PD-resistant grapevines.
 
Article
Fungal infections of vineyard grapes compromise the yield and sensory properties of wines. Consequently, there is a need for more effective fungal control measures. The aim of this work was to evaluate the potential of a novel lipopeptide fungicidal formulation to control these diseases. A mixture of rhamnolipids (RLs) and the lipodepsinonapeptide syringomycin E (SRE) showed greater inhibitory activities than SRE alone against fungi isolated from grape berries and stems of a heavily infected vineyard in Louisiana. The fungal species tested were Aspergillus japonicus, Cladosporium cladosporioides, Curvularia brachyspora, Greeneria uvicola, Nigrospora sphaerica, Trichoderma sp., Penicillium sclerotiorum, and P. thomii. Exposure to SRE resulted in 50% killing of germinating conidia of all these fungal species at concentrations between 0.75 and 3 µM and the SRE + RL mixture gave 50% killing between 0.75 and 1 µM SRE. Nongerminated conidia of only C. brachyspora were killed by SRE alone or SRE + RLs (both giving 50% killing at <1 µM SRE). The RLs alone did not affect the growth of either germinating or nongerminating conidia of these fungi. Results demonstrate the potent and broad fungicidal properties of SRE and show that when mixed with RLs, it is even more lethal to a wide range of grape-associated fungi in the germination stage.
 
ratios tests for relatedness between pairs of individuals.
Article
The rootstock Freedom is the offspring of two open-pollinated parents (1613-59 and Dog Ridge 5), sources of root-knot nematode resistance. As phylloxera has increased in importance in vineyards, the risk of Vitis vinifera-derived phylloxera susceptibility from the unknown pollen donors is a concern. To clarify the pedigree of Freedom, genetic profiles of 31 potential progenitors were analyzed with 30 microsatellite markers. We confirm the reported parent (1613-59) and grandparent (1613C) of Freedom and identify 3306C (V. riparia x V. rupestris) as the pollen parent of 1613-59. We were unable to identify the pollen parent of Dog Ridge 5.
 
Article
Phylloxera has been an important pest in California since its discovery in 1880 within Sonoma and Napa counties. Phylloxera-resistant rootstocks and germplasm were selected from American grape species native to the eastern United States. Breeding programs to develop improved phylloxera-resistant rootstocks were started in the late nineteenth century. Resistance to phylloxera has been reported to be controlled by several genes. To focus on one aspect of resistance to phylloxera, a greenhouse screening method was used to observe absence/presence of root nodosities produced by phylloxera. Only one source of phylloxera biotype A from Fresno County was used to reduce the complication of various biotypes. Grape rootstocks with known field reaction to phylloxera were evaluated to test the reliability of the greenhouse test. A design II mating factorial cross was made between male and female rootstocks with a range of resistance to susceptibility. The reaction of their progeny to phylloxera was observed in the greenhouse. All populations segregated for resistance/susceptibility with a few exceptions. Dog Ridge crossed with two susceptible genotypes gave all susceptible offspring. Kober 5BB crossed with susceptible or resistant genotypes gave all resistant offspring. The segregation of resistance to nodosity development could be explained by two complementary dominant genes in most families.
 
Article
For irrigation design and scheduling, water use of crops is commonly estimated from grass reference evapotranspiration (ET0) estimates multiplied by published crop coefficients (kc). This method is assumed to stabilize kc across climates because of the response of ET0 to meteorological variables. However, the simple application of reference grass-based kc models may not be accurate in a cool, humid climate, especially for sparse and tall crops where stomatal regulation is well-coupled to bulk air and sensible and latent heat exchanges may have a different dynamic than in grass. The aim of this work was to measure actual transpiration in a vineyard in the humid climate of New York and compare the results with the estimates obtained using the reference grass-based crop coefficient model. Measurements of water use in Concord grapevines (Vitis labruscana Bailey) were made with heat-balance sap-flow gauges calibrated against canopy gas exchange chambers. Daily ET0 was estimated from meteorological data acquired by a nearby weather station. Daily transpiration rates per single vine ranged between 15 and 40 L day-1, with hourly rate peaks of 4 L hr-1. Water use declined during the hottest and driest part of the season, probably due to either water or heat stress. Results suggest that even in humid climates, grapevines might require irrigation occasionally. The reference grass-based kc was inadequate to quantify the degree of coupling between stomatal regulation of transpiration and bulk air conditions, specifically vapor pressure deficit. Overall, results suggest the necessity of developing crop-specific models for water management.
 
Article
This research focused on the development of a molecular assay, based on the amplification of 11 simple sequence repeats, that is useful to combine varietal identification with skin color discrimination of less-colored/col-orless mutants from a black wild-type cultivar (like Pinots). The proposed molecular toolkit was reliable using both purified and unpurified DNA obtained from leaves, thereby speeding up the time required for laboratory analyses and lowering the costs of the molecular outcome. © 2017 by the American Society for Enology and Viticulture. All rights reserved.
 
Article
Monastrell grape skins show a high percentage of galactose, likely due to low β-galactosidase activity. Little is known about the characteristics of this enzyme. A simple method to extract and partially purify β-galactosidase from grape berry skin is presented. The kinetic properties of this enzyme are comparable to those of β-galactosidase from other fruits. In this method Triton X-114 (a non-ionic detergent) has a double effect: solubilizing skin components to liberate the enzyme and removing most phenols and hydrophobic proteins, giving rise to a 56-fold increase in specific activity. The method proposed may be useful to easily extract and partially purify this enzyme during grape berry ripening. Copyright © 2010 by the American Society for Enology and Viticulture. All rights reserved.
 
Article
β-Galactosidase from grape berry pulp was extracted after a 2 hr digestion with the non-ionic detergent Triton X-114. Subsequent phase partitioning eliminated ∼75% of the phenolic compounds, enabling the enzyme to be recovered in the aqueous upper phase with an 8-fold increase in its specific activity. The enzyme was kinetically characterized using o-nitrophenyl β-galactopyranoside as substrate and was active at acidic pH with an optimum at pH 4.2, a value at which Vmax and Km were 0.009 μmol/min/mg protein and 1.2 mM, respectively. β-Galactosidase was competitively inhibited by free galactose with Ki of 0.8 mM. The enzyme had an optimum temperature of 65°C, although its thermostability is very low at this temperature.
 
Chronogram of Bayesian divergence time estimates of Vitis BEAST software (taken from Wan et al. 2013, Figure 3). Gray bars represent 95% highest posterior density intervals of nodal age in million years. Black text represents outgroups and Vitis species not used in this study. Shaded boxes represent Vitis species and their assigned clades.
Climatic niche models of 13 native North American Vitis species produced by Maxent. Climate suitability ranges from no suitability (0; green) to high suitability (1; red).
Summary of native North American Vitis species in climate climatic niche. Ellipses encircle the extent of the niche for each clade, with species that belong to each clade delimited by the same colored text. Arrows link the centroids of one clade to the next that contains more-recently derived species.
Overlap values.
Modeling summary.
Article
Climate change models predict that sites suitable for vineyards will shift over the next 50 years. In part through rootstocks and hybrid scions bred from North American Vitis species, cultivated grapevines can thrive in a variety of environments. However, relatively little is known about the range of climatic conditions under which natural populations of native North American Vitis species occur. In this study, we use geographic information system data to describe the climatic niches of 13 North American Vitis species that are distributed east of the Rocky Mountains and to compare climatic niches in a phylogenetic context. We extracted bioclimatic data from thousands of locality points and performed univariate and multivariate statistical analyses for each Vitis species. We then used these data to determine if phylogenetic relatedness was associated with similarities or differences in climatic niches. Finally, we performed Maxent modeling and multivariate environmental similarity surfaces analysis to identify suitable climate space for each species throughout the United States. Our results indicate Vitis species occur under a wide range of climatic conditions, including warm and wet (V. shuttleworthii), warm and dry (V. mustangensis), cold and wet (V. labrusca), and cold and dry (V. riparia) climates. Some clades within Vitis exhibit similarities in their climatic niches (niche conservatism), while others include species with notably different climatic niches (niche divergence). Additionally, we identify novel geographic locations where some species could potentially flourish. These data provide valuable insights into the abiotic environments occupied by natural populations of North American grapevines and may be useful in the development of rootstock genotypes to suit specific climates now and in the future.
 
Article
Grapevines (Vitis vinifera L.) are often cultivated under suboptimum conditions for both water and nutrients in order to enhance the quality of grapes for making wine. Since water supply and nitrogen nutrition are major determinants of photosynthetic activity, this study investigated the potential of leaf delta C-13 and delta N-15 to explain spatial variations in biomass production as a function of water use efficiency and fertilizer N uptake, respectively. The combined isotopic signal of the leaves, together with pruning weight, leaf nutrients, and soil properties, were measured in randomly selected field positions over two growing seasons in two fertilized, but different, Merlot vineyards. Significant correlations of surface soil properties and leaf nutrients with pruning weight were not great enough to explain spatial patterns in biomass production. In contrast, leaf delta C-13 and delta N-15, when used as independent variables in multiple regression, explained 71 % of the spatial variation of pruning weight across both fields and growing seasons. Most of the explained model variability was attributed to leaf delta N-15 (r(2) = 0.54), but within single years leaf delta C-13 was better correlated to biomass. The negative correlation between these two isotopes and pruning weight was high only within the vineyard that had steep topographic features and spatially variable growth patterns. It indicated a response of vines to adverse soil conditions by a progressive reduction of water use efficiency and an increase in fertilizer N uptake downslope from the low- to the high-biomass areas of this field. If these relationships persist in other fertilized and water-stressed fields, the isotopic signature of the leaves may be an important tool for application of site-specific management practices within single vineyards.
 
Percent N from nitrate (NO3-N) to total N (TN) ratio for petioles ( P ) and leaves ( L ) at bloom.
tissue analyses of leaves sampled opposite to clusters at anthesis. Other information is as found in Table 1.
Article
A study was conducted to investigate the interaction of N fertilization rates and different irrigation amounts on N fertilizer recovery efficiency (REN) of Cabernet Sauvignon in a commercial vineyard near Oakville, California. The fertilizer treatments consisted of a control (no fertilizer) and two N-15 labeled ammonium nitrate fertilizer applications (6.5 and 13.0 g N/vine). The N fertilizer was applied two weeks before anthesis. The irrigation treatments were various fractions (0.25, 0.5, and 1.0) of estimated vineyard water use (ETc), with the applied water amount for the 1.0 irrigation treatment from 7 Apr to 9 Sept equivalent to 312 mm. Midday leaf water potential (Psi(l)) was measured throughout the season to monitor vine water status. The labeled N fertilizer was detected in the petioles and leaf blades two weeks after application. Irrigation and fertilization treatments significantly affected midday Psi(l). There were significant differences in aboveground vine biomass among the treatments. In general, those supplied with more water and/or N fertilizer had greater biomass compared with nonfertilized vines under deficit irrigation. Vine uptake of the N-15 labeled fertilizer increased with increasing fertilization rates and irrigation amounts. The REN was significantly different between the two N-15 fertilizer treatments (29% for 6.5 g N/vine and 24% for 13.0 g N/vine). REN at harvest for the 0.25, 0.5, and 1.0 ETc irrigation treatments was similar to 24, 28, and 27%, respectively, although not significantly different. The data indicate that fertilizer amount had a significant effect on REN under the conditions of this study and that irrigation rates at full ETc tended to increase REN in this vineyard when compared with deficit irrigation.
 
Blade tissue analyses of leaves sampled opposite to clusters at anthesis. Other information is as found in Table 1. 
Percent N from nitrate (NO3-N) to total N (TN) ratio for petioles ( P ) and leaves ( L ) at bloom.
tissue analyses of leaves sampled opposite to clusters at anthesis. Other information is as found in Table 1.
Article
A study was conducted to determine the N fertilizer recovery efficiency (REN) of Vitis vinifera L. cv. Thompson Seedless grown in the San Joaquin Valley of California. Vines were drip- or furrow-irrigated and fertilized with 15N-labeled potassium nitrate (KNO3) or ammonium sulfate (NH4)2SO4. The fertilizers were applied shortly after anthesis with a single application of 25 g N/vine (~28 kg N/ha). An additional set of the drip-irrigated vines was fertilized 10 times beginning 20 April across a 20-week period during the growing season with labeled KNO3 (amounts equivalent to ~31 kg N/ha). Total biomass, N concentrations, and 15N of all vine organs, including the root system, were measured. There were no significant differences in REN(~40%) between the two fertilizer types (nitrate versus ammonium) for the drip-irrigated vines or for the comparison of a single application of KNO3 to a split application of that fertilizer applied every two weeks. The REN of furrow-irrigated vines was ~12%. The partitioning of 15N-labeled fertilizer taken up by the vine was significantly affected by fertilizer treatment. Approximately 47% of the ammonium fertilizer for the drip-irrigated vines was found in the clusters, while only 30% of the nitrate fertilizer for the split application of the fertilized, drip-irrigated vines was found in the clusters. The greatest amount of fertilizer N found in the roots was for the nitrate fertilized vines under drip-irrigation (both single and split applications). The results indicated that irrigation type greatly affected REN of the N fertilizers used in the study, and that irrigation and fertilizer type affected the distribution of N once it was taken up by the vine. © 2015 by the American Society for Enology and Viticulture. All rights reserved.
 
Article
Information on fate of nitrogen applied to vines is needed to improve fertilizer management. Nitrogen-15 enriched ammonium and nitrate fertilizers were applied in the spring through a trickle irrigation system to six Thompson Seedless vines of a vineyard on the West Side of the San Joaquin Valley of California. At fruit harvest, all above-ground plant parts were removed and analyzed for 15N. Soil around each vine was also sampled and analyzed for 15N in the inorganic and organic N fractions. Spatial patterns of fertilizer N for soil inorganic and organic N were analyzed using a median polish technique which indicated large variability with respect to direction, distance, and depth. There was a tendency for the fertilizer N from NH4 to be located directly beneath emitters than from the NO3. Nitrogen from the NH4 application penetrated to only the 150-cm depth, whereas some N from the NO3 application reached 210 to 240 cm. Most of the organic fertilizer N for both NO3 and NH4 applications was in the top 60 cm of soil where the vine roots were likely of greatest density. Overall recovery of fertilizer N was also quite variable, probably due to variability in soil physical properties and uneven surface application of water and fertilizer due to local surface ponding. Although not statistically significant, uptake of fertilizer N by above-ground plant components was slightly higher for the NH4 application (24.2% of applied N) than the NO3 application (21.5%). Soil organic N had significantly (95% level) higher N from NH4 (19% of applied N) than from NO3 (13%). This probably occurred due to longer residence time of N from NH4 within the top 60 cm, where the bulk of roots and microbial activity existed, than for NO3. Overall, about 67% to 79% of the fertilizer N applied in spring remained in the soil at harvest, and the vines took up the rest. There was no indication of significant N leaching below 2.4 m or denitrification of fertilizer N for the trickle-irrigated vines during the growing season.
 
Article
Weather conditions have a significant impact on crops, and temperature is one of the main factors that controls plant development. Thermal time models based on temperature have been applied to predict the development of many species. To implement these models, determination of an appropriate base temperature (T-b) is required to characterize the differences among developmental stages and cultivars. The goal of this study was to determine the unique Tb and degree-days (DD) to predict budbreak, bloom, and veraison for 17 cultivars. T-b's were estimated with the minimum variance method using phenological data collected over 23 years in Prosser, WA. Tb increased throughout grapevine development and ranged from 6.1 to 8.4 degrees C for budbreak, from 7.2 to 10.5 degrees C for bloom, and from 9.4 to 12.8 degrees C for veraison. Starting DD accumulation on 1 Jan and using the Tb's estimated for each cultivar, the duration to budbreak ranged from 78 to 180 DD, from budbreak to bloom ranged from 240 to 372 DD, and from bloom to veraison ranged from 556 to 800 DD. Errors in prediction varied between 4.8 and 7.8 days to budbreak, between 1.9 and 5.5 days to bloom, and between 7.1 and 12.4 days to veraison. Based on the errors in prediction, models that used an estimated T-b specific for a phenological stage performed better than models that had a fixed T-b of 0 and 10 degrees C. The estimated thermal time parameters provide a simple approach for characterizing differences among cultivars and assist growers and industry in implementing management practices through simple decision support tools based on thermal time models.
 
Article
Filtration is essential for red wine stability and yet the effect on wine colloids and sensory properties, such as texture, remains a concern. Small-scale investigations have demonstrated the loss of color and polysaccharides, however the effect of commercial-scale filtration on red wines is unknown. Samples of four commercial wines (Cabernet Sauvignon (CAS) and Shiraz from 2013 and 2014 vintages) were collected from two commercial bottling facilities before and after cross-flow filtration and lenticular filtration; after 0.65 μm membrane; and after 0.45 μm membrane filtration. CAS 2014 wines were filtered through both polyether sulfone (PES) and nylon 0.45 μm membranes. The average size of particles in all wines decreased significantly with cross-flow filtration and the concentration of polysaccharides decreased with 0.45 μm filtration, while tannin and color remained unchanged. After 18 months bottle-aging, the average particle sizes of filtered and unfiltered 2013 wines were similar, while the filtered 2014 wines contained smaller particles than the unfiltered wines. Sensory analysis showed no consistent filtration-related trends in textural attributes across all wines, although there were some significantly different aroma or flavor attributes for samples of different filtration grade within each wine. These results suggest that commonly applied commercial-filtration practices have no impact on wine color and minimal impact on sensory profiles of red wines.
 
Article
Procedures to analyze pesticides in wines were developed and evaluated. Wine samples were applied to solid-phase extraction cartridges (C-18, octadecyl), and pesticides were eluted with ethyl acetate. The reduced solvent extracts were subsequently screened and analyzed by gas chromatography-mass spectrometry using full scan or selected ion monitoring. Target and qualifier ions and retention times were used to screen, confirm, and determine recoveries of 48 common pesticides. Various parameters including pesticide spike concentrations, wine type (red and white), and salt addition prior to extraction were compared and evaluated for highest extraction efficiencies and optimal sensitivity in spiked wine samples. Suitable recoveries to most pesticides at the 0.01 and 0.10 mg/L fortifications were obtained by adding sodium chloride prior to extraction and ethyl acetate elution. These findings confirm that this is a fast and effective method for identifying several types of pesticides in wines.
 
Article
A partial or even complete substitution of icewines by other wines of high quality but harvested under non-icewine conditions has to be anticipated in vintages of unfavorable mild winters. Although stable isotopes reflect incomplete phase transitions and are therefore potentially well suited for icewine authentication, this technique has not yet been applied as an analytical tool against icewine frauds. As a first approach, this study shows that icewine authentication is best achieved by measuring the difference of δ18O values between the water of icewine musts and the remaining water in their grape marcs. A positive difference indicates a fraud. Furthermore, this difference was found to be related to the increase in sugar in the must due to cryoconcentration. Hence, this difference also allows estimation of the extent of cryoenrichment. By measuring 47 commercially produced icewine musts and their corresponding grape marcs, an average difference of ∼1.7‰ was observed in vintage 2012 in Germany. This difference corresponds to an average cryoenrichment of ∼150% (i.e., an increase over the initial must weight by a factor of 1.5). © 2014 by the American Society for Enology and Viticulture. All rights reserved.
 
Article
A long-term (1964-2009), multiple Vitis vinifera L. cultivar data set has provided a comprehensive assessment of cultivar similarities/differences in phenological timing and growth phases and relationships with climate and climate change in the Veneto region of Italy. The budbreak to harvest period for the cultivars studied covered mid-April to late September, averaging 156 days but varying 55 days across cultivars. The main phenological events and intervals between events exhibited a 25 to 45 day variation between the earliest and latest years, with the bloom to veraison growth interval showing the lowest vintage-to-vintage variation. From 1964-2009, trends of 13 to 19 days earlier were found for bloom, veraison, and harvest dates, while budbreak exhibited high interannual variation and no trend. There were similar characteristics and trends for the main phenological events for early, middle, and late maturing cultivars, although early maturing cultivars changed at a higher rate. Changes in climate in the region led to significant breakpoints in the phenology time series, averaging 1990-1991 across all cultivars, with early and middle cultivars shifting sooner than late cultivars. Growing season average temperatures warmed 2.3 degrees C from 1964-2009, while annual and seasonal precipitation amounts did not change significantly. From 1964-2009, the growing period climate differences were 2.0 degrees C between the years with the shortest and the longest budbreak to harvest intervals. The combined trends in phenology and climate resulted in an average shift of eight days per 1.0 degrees C of warming. The extremely warm summer of 2003 (compressed growth intervals) and warm spring of 2007 (shifts in phenological timing) provide analog conditions to those projected for later this century.
 
Top-cited authors
Linda F Bisson
  • University of California, Davis
Andrew Reynolds
Andrew Waterhouse
  • University of California
S. E. Spayd
  • North Carolina State University
Denis Dubourdieu
  • Université Victor Segalen Bordeaux 2