Labrusca Cultivars Research Articles

Successful management of Grapevine leaf spot with fungicides programs to avoid infections of primary inoculum

Grapevine leaf spot (GVLS) (Pseudocercospora vitis) occurs at the end of the cycle of Vitis labrusca cultivars. A fungicide application program, considering preventive applications, has not been studied to control GVLS. The objectives of this study were i) to evaluate the effect of fungicide programs, with different application start dates, on GVLS epidemics in the field and ii) to test the efficacy of fungicides in preventative applications to control GVLS in a greenhouse. The field experiment was carried out in the municipality of Campo Largo, Paraná, Brazil, during 2019/20, 2020/21, and 2021/22 seasons of the Bordô cultivar. In each season, six fungicide programs, with different application start dates, and a control, without application, were evaluated and compared. In the greenhouse, grape seedlings were treated with seven different fungicides, and 24 h later they were inoculated with P. vitis. In the field, the maximum asymptote, an important epidemiological parameter, was lower in the treatment with fungicide applications carried out from the 6th (flowering) to the 18th week after budburst (after harvest). This treatment was carried out at fortnightly intervals, rotating the active ingredients copper oxychloride, pyraclostrobin + methiram, and difenoconazole. In the greenhouse, the fungicides mancozeb, chlorothalonil, difenoconazole, and the methiram + pyraclostrobin mixture had control efficacy above 80% in relation to the untreated control. The results suggested that reducing primary P. vitis infections, which can occur from the beginning of the grapevine cycle, is an important strategy for controlling GVLS in the subtropical climate.

Investigation of Brazilian grape juice metabolomic profile changes caused by methyl jasmonate pre‐harvest treatment

SummaryGrape juice is a major source of potential health‐promoting bioactive polyphenols, especially for children and those who do not consume wine. Since the subtropical climate may negatively affect the concentrations of grape polyphenols, especially anthocyanins, elicitors such as methyl jasmonate (MeJa) could be used to promote polyphenol biosynthesis. This work aimed at investigating the impact of MeJa treatment on grape juice produced via a traditional low‐cost process from two Vitis labrusca cultivars and in two Brazilian regions. The untargeted LC–MS analytical protocol demonstrated that Isabel Precoce juices strongly benefited from MeJa treatment, especially regarding their anthocyanic profile, regardless of the cultivation region. Known MeJa markers in wine and V. vinifera grapes (flavanols, flavonols and stilbenes) in this experiment had mixed behaviours depending on the region/variety/cultivation. Moreover, it was found that all the detected hydroxycinnamates were influenced by the treatment, especially the concentration of their glucosides, which was increased. Glutathione, 2‐S‐glutathionyl caftaric acid and indole lactic acid glucoside were identified for the first time as MeJa treatment biomarkers in grape products, indicating a possible positive effect on juice antioxidant properties.

Development and validation of a standard area diagram set to estimate severity of grapevine downy mildew on Vitis labrusca

The aim of the present study was to develop and validate a standard area diagram set (SADs) to evaluate severity of grapevine mildew (Plasmopara viticola) for Vitis labrusca cultivars. SADs contain 10 disease severity levels (0.5; 2; 5; 10; 20; 30; 40; 50; 60 and 72%). Validation was performed using a sequence of 50 images assessed by 16 raters with no previous experience in quantifying plant disease severity. By Lin’s concordance correlation coefficient analysis, there was an improvement in u (no SADs = 0.361, with SADs = −0.030), υ (no SADs = 1.456, with SADs = 0.997), Cb (no SADs = 0.864, with SADs = 0.979), r (no SADs = 0.897, with SADs = 0.937) and ρc (no SADs = 0.774, with SADs = 0.918) parameters, showing an increase in accuracy and precision of the estimated disease severity using SADs when compared to the non-use of SADs. Reliability improvement was also observed, with increase in R2 values when SADs were used (no SADs = 0.790, with SADs = 0.846). Therefore, SADs improved accuracy, precision and reliability of grape downy mildew severity estimates in Vitis labrusca.

Understanding components of the grapevine leaf spot monocycle and comparing resistance of Vitis labrusca cultivars

Grapevine leaf spot caused by Pseudocercospora vitis is important at the end of the vegetative cycle of Vitis labrusca and its hybrids, but studies on this pathosystem and its monocyclic components are scarce. The objective of this work was to determine the favorable conditions for the development of the pathogen and to study the resistance levels in 10 grapevine cultivars. The germination of P. vitis conidia was evaluated at temperatures from 4 to 35 °C, germ tube size from 8 to 33 °C and weight of colonies of the pathogen from 10 to 40 °C. Wetness periods of 3 to 48 h were also evaluated for germination at temperatures from 10 to 40 °C. In five cultivars of V. labrusca and five hybrids inoculated with P. vitis, the incubation period and the progression of disease severity under controlled conditions were compared. The optimal temperature for germination of P. vitis was at 28 °C and 27 °C for germ tube growth. For mycelial weight the optimum temperature was 26.4 °C. The highest germination of the pathogen occurred with wetness of 45.5 h and temperature of 29.6 °C. The incubation period in the cultivars ranged from 26 to 51 days. The disease progress curve showed differences among cultivars tested, ‘Concord’ and ‘BRS Vitoria’ being the most resistant. In plants inoculated at 25 °C, the number of lesions increased over time, stabilizing at 42–47 days after inoculation and from here no new lesions appeared, only lesions expansion was observed.

The influence of table grape rootstock and cultivar combinations on susceptibility to downy mildew

Downy mildew (Plasmopara viticola) is among the most important grape disease in the world. Disease control is mostly based on preventive management, including reduction of overwintering inoculum, green pruning, use of less susceptible cultivars, and fungicide applications. The objective of this study was to describe the incidence and severity of P. viticola and the resulting defoliation in three Vitis labrusca cultivars (‘Concord,’ ‘Bordo’ and ‘BRS Carmem’) grafted onto three different rootstocks (Paulsen 1103, IAC 766 and VR 043–43) in a commercial vineyard in a subtropical area. To compare the responses of each cultivar and rootstock combination, the experiments were carried out on ridges with a semi-trellis system. Disease incidence and severity were assessed every 14 days from September to March in 2011–2012 and 2012–2013 on the last 10 leaves of specific shoots on six plants of each of the nine different combinations. During the growing season, weather conditions were favorable to the development of the disease. Symptoms started in the vegetative phase and continued during fruiting. There were significant differences between cultivars with ‘BRS Carmem’ being the most susceptible to downy mildew and ‘Concord’ the least susceptible, but rootstocks had no significant influence on downy mildew severity.

Determination of Downy mildew and Powdery Mildew Resistance of Some Grape Cultivars and Genotypes

Different grape cultivars of Vitis species have been cultivated in Turkey since ancient times. A large proportion of these cultivars cannot be cultivated in the humid regions of the country due to downy mildew (Plasmopara viticola) and powdery mildew (Uncinula necator or syn. Erysiphe necator) diseases. Cultivars resistant to these diseases can generally grow without any or fewer fungicide applications. However, there are also differences in the resistance level of cultivars. In particular, Vitis vinifera cultivars, the most widely cultured species, are most affected by these diseases. Thirteen V. vinifera cultivars, eight V. labrusca cultivars and six interspecific cultivars were used in this study, for a total of 27 cultivars. The resistance of cultivars against downy mildew and powdery mildew was determined over two years with natural infection and artificial inoculation applications. Generally, all cultivars showed more resistance to downy mildew, while they also showed lower resistance to powdery mildew. The evaluation based on species found V. vinifera to be the most sensitive. While interspecific cultivars were found to be most resistant to downy mildew, V. labrusca cultivars were the most resistant to powdery mildew. Among cultivars of the same species, however, differences in terms of resistance were observed. These differences can be used in breeding studies in order to obtain new, disease-resistant cultivars, which may be grown commercially to comply with good agricultural practices (GAP) or organic viticulture in the future.

Relations between downy/powdery mildew diseases andsome phenolic compounds in Vitis spp.

Powdery mildew and downy mildew are among the most important diseases of grapevine. The relationship between these diseases and phenolic components has become increasingly important in recent years. This study evaluated changes of total phenolics, total antioxidant activity, and phenolic compounds (gallic acid and rutin hydrate) in some Vitis species. Vitis labrusca cultivars or genotypes, Vitis vinifera cultivars, interspecies hybrids, and a Vitis rotundifolia cultivar's healthy and infected leaves were examined. The contents of healthy material and of samples of plant material infected with both microorganisms (Uncinula necator (Schw.) Burr and Plasmopara viticola (Berk. & M.A. Curtis) Berl & De Toni) were determined. In general, the content of all compounds, except rutin hydrate, increased in infected leaves. After infection with powdery mildew, the increase was particularly significant. The total phenolic content rose after infection but varied with the cultivar and species. The highest antioxidant activity (598.96 μM TE/100 g) and total phenolic levels (2248.27 mg GAE/100 g) were identified in V. vinifera 'Italia', which is known to be sensitive to fungal diseases. On the other hand, the highest levels of gallic acid (9.26 mg/100 g) were identified in V. rotundifolia 'Sugargate', which is known to be resistant to fungal diseases. The highest levels of rutin hydrate (60.44 mg/100 g) were identified in V. vinifera 'Red Globe'. There was a significant positive correlation between total phenolics and total antioxidant after both diseases (0.7556-0.6904).

Suscetibilidade de bagas de genótipos de videira pela infestação por Drosophila suzukii (Diptera: Drosophilidae)

Resumo: O objetivo deste trabalho foi avaliar a suscetibilidade de genótipos de videira à drosófila-da-asa- manchada, Drosophila suzukii (Diptera: Drosophilidae), em bagas de uva intactas e em bagas infestadas após a ocorrência de puncturas, causadas pela oviposição da mosca-das-frutas sul-americana [Anastrepha fraterculus (Diptera: Tephritidae)] ou por danos mecânicos (alfinetes). Os experimentos foram realizados em laboratório, a 22±1°C, umidade relativa de 65±10% e fotófase de 12 horas. A suscetibilidade foi avaliada para 18 genótipos de videira, em bagas intactas submetidas às fêmeas de D. suzukii. O potencial de interação foi verificado em bagas de uva 'Italia', cuja epiderme foi danificada por puncturas de A. fraterculus ou por alfinete, em comparação a frutos de morango 'Albion'. As cultivares de Vitis labrusca 'Niagara Rosada' e 'Concord' não foram infestadas por D. suzukii, e cinco dos oito genótipos que foram infestados são cultivares melhoradas. A infestação de D. suzukii em bagas de uva 'Italia' com danos mecânicos, feitos com um alfinete ou pela oviposição de A. fraterculus, foi semelhante à de bagas íntegras. Há baixa adequação hospedeira de videiras a D. suzukii, mesmo com a presença de danos. As cultivares 'Benitaka', 'BRS Vitória' e 'BRS Morena' são as mais suscetíveis a D. suzukii.

CARACTERIZAÇÃO FÍSICO-QUÍMICA E SENSORIAL DE VINHOS BRANCOS DA REGIÃO NOROESTE DE SÃO PAULO

Os vinhos brasileiros são apreciados pelos consumidores por apresentar aroma e gosto suave e frutado típico das cultivares Vitis labrusca. Essas espécies, diferentemente das Vitis vinifera, não necessitam de estruturas tecnológicas diversificadas para o processo de vinificação e, além disso, não apresentam períodos de entressafra, aumentando a produtividade. O processo de vinificação dessas cultivares difere do processo referente às uvas viníferas principalmente no que se refere à etapa de envelhecimento, muitas vezes inexistente, influenciando na cor e no teor de compostos fenólicos dos vinhos de mesa. Além da tecnologia de vinificação, o estágio de maturação da uva e as condições ambientais de produção influenciam na qualidade química e sensorial dos vinhos dessas cultivares. Nesse sentido, o objetivo central desse artigo é analisar a qualidade de vinhos brancos provenientes de vinícolas da região noroeste do estado de São Paulo, por meio de determinações físico-químicas e caracterização de perfil sensorial. Três vinhos dessa região (dois brancos de mesa e um branco fino) foram avaliados por meio de métodos analíticos e sensoriais. Os dados foram analisados estatisticamente por aplicação de testes estatísticos paramétricos, não-paramétricos e por Análise de Componentes Principais (ACP). Observaram-se diferenças significativas (P

Composição do suco de uva caseiro de diferentes cultivares

Um volume considerável de uva do grupo das americanas da Serra Gaúcha é destinado para a produção de suco de uva caseiro. O objetivo do presente trabalho foi avaliar o efeito das cultivares Isabel, Bordô (Ives) e Concord de Vitis labrusca e Cabernet Sauvignon de Vitis vinifera, na composição do suco de uva, elaborado na Embrapa Uva e Vinho na safra de 2003. Os sucos foram avaliados quanto às análises clássicas: densidade, °Brix, acidez total, acidez volátil, pH e relação °Brix/acidez total, efetuadas através de métodos físico-químicos. Os compostos voláteis etanol, metanol e aldeído acético foram determinados através da cromatografia gasosa. Os elementos minerais Ca, Mg, Mn, Fe, Cu e Zn foram analisados por absorção atômica, enquanto que o K, Na e Rb, por emissão de chama. O P foi determinado por colorimetria. Os resultados evidenciaram variabilidade entre os sucos das diferentes cultivares. O suco de Cabernet Sauvignon diferenciou-se dos demais pelos menores teores de metanol e etanol e pelos maiores de acidez volátil e Fe. Os sucos da uva Bordô e Concord apresentaram menor teor de acidez total e de Mn.

Long-term study of somatic embryogenesis from anthers and ovaries of 12 grapevine (Vitis sp.) genotypes

Anthers and ovaries of six grapevine cultivars (three Vitis vinifera L., two V × Labruscana L. H. Bailey, and one complex hybrid) were extracted from flower buds over 2 yr and cultured on three media reported to promote somatic embryogenesis in Vitis tissues. The highest percent embryogenesis from the hybrid ‘Chancellor’ and V. vinifera ‘Chardonnay’, ‘Merlot’, and ‘Pinot Noir’ occurred on medium C [Nitsch and Nitsch, 1969, basal medium with 3.0% (w/v) sucrose, 0.01% (w/v) inositol. 0.3% (w/v) Phytagel, 2.5 μM 2.4-dichlorophenoxyacetic acid, 2.5μM β-naphthoxyacetic acid, 5.0μM N-(2-chloro-4-pyridyl)-N′-phenylurea, and 0.05% (w/v) glutamine]. Regardless of the media, the labrusca cultivars ‘Concord’ and ‘Niagara’ produced soft non-embryogenic callus that was sometimes mixed with well-developed somatic embryos. Nine vinifera genotypes were further tested for several different years on medium C. Embryogenic cultures suitable for transformation were obtained from all genotypes in more than 1 yr. The average percent embryogenesis from ovaries was 7-fold higher than from anthers. There was significant annual variation in percent embryogenesis, demonstrating the need for media comparisons to be replicated for more than one season. Suspension cultures suitable for use in genetic transformation were initiated from ‘Chardonnay’, ‘Merlot,’ and ‘Pinot Noir’ pro-embryogenic masses. ‘Chardonnay’ suspension cultures plated and grown under conditions developed for recovery of plants after biolistic transformation yielded approximately 500 non-transformed embryos per plate after 4 mo. of culture, with 68.6% of the embryos converting to plants. This is the first reported protocol for embryogenesis from ‘Concord,’ ‘Cabernet Franc,’ and ‘Pinot Noir’ grapevines.

Colonization of New York Vineyards by Anagrus spp. (Hymenoptera: Mymaridae): Overwintering Biology, Within-Vineyard Distribution of Wasps, and Parasitism of Grape Leafhopper, Erythroneura spp. (Homoptera: Cicadellidae), Eggs

A study was conducted in New York to identify the Anagrus species present in vineyards, to determine the plants in which Anagrus species overwinter, and to characterize the dispersal of wasps and level of parasitism of grape leafhopper eggs in vineyards. Anagrus daanei S. Triapitsyn and Anagrus erythroneurae S. Trjapitzin and Chiappini were the most abundant species reared from Vitis labrusca Bailey and Vitis vinifera L. cultivars, respectively. V. labrusca cultivars are infested predominantly by Erythroneura comes (Say), whereas V. vinifera cultivars are infested primarily by the Erythroneura vitifex Fitch–Erythroneura bistrata McAtee complex. Anagrus tretiakovae S. Triapitsyn was reared from seven grape cultivars in approximately equal proportions. Thus, A. daanei and A. erythroneurae appear to possess greater degrees of host specificity than A. tretiakovae. These results support the belief that, although Anagrus species have relatively broad host associations, host preferences do exist. These preferences may be mediated by the plant associations of particular leafhopper species. Anagrus species use alternate hosts that infest several plant species. In particular, diapausing insect eggs in Acer saccharum Marshall, Robinia pseudo-acacia L., Rosa multiflora Thunberg, Salix nigra L., Vitis riparia Michaux, and Zanthoxylum americanum Miller may play important roles in the overwintering biology of the Anagrus species that are most abundant in vineyards. Following emergence from overwintering hosts, Anagrus adults are aggregated at the vineyard edge early in the season (May and June). By midseason or later (August and September), the pattern of wasp colonization and parasitism indicates that parasitoids are more widely dispersed in the vineyards. This pattern is consistent with colonization from vineyard edges, followed by relatively slow dispersal into the vineyard interior. Further investigations are necessary to identify the alternate host(s) that Anagrus exploits during the winter and spring and to delineate the phenology of such alternate hosts, as well as that of the grape leafhoppers and Anagrus species in the spring. Habitat management studies could then be conducted to identify strategies that would accelerate population growth of Anagrus in the spring and increase the rate of dispersal into vineyards.

RFLP and RAPD Analysis of Wild and Cultivated Grapes (Vitis spp.).

Restriction fragment length polymorphism (RFLP) and random amplified polymorphic DNA (RAPD) analyses were used to analyze the relations among wild grapes in Japan, Korea, and China, and cultivated grapes. RFLP analysis of an intergenic spacer region of ribosomal DNA revealed that all the tested species and varieties of Vitis had their specific banding patterns with some variations among the samples. RAPD data obtained, using the primers OPA01, OPA02, OPA11, OPB01, and OPB06, were clustered by UPGMA. A phenogram of 24 samples of wild grapes and 16 samples of cultivated grapes showed a clear separation between wild and cultivated grapes. Oriental and occidental cultivars of V. vinifera formed separate clusters, which, together, formed a higher cluster that was separate from a cluster formed by the V. labrusca cultivars. Although 'Koshu' was found to be a part of the cluster of oriental cultivars of V. vinifera, as it has been considered to be, the RFLP pattern of 'Koshu' has two weak bands which were not found in other cultivars of V. vinifera.

Varietal Preferences of Erythroneura Leafhoppers (Homoptera: Cicadellidae) Feeding on Grapes in New York

Species composition of Erythroneura leafhoppers infesting the 3 major classes of grapes grown in New York was investigated. Eastern grape leafhopper, E. comes (Say), comprised 74–100% of populations collected on the native American ( Vitis labrusca Bailey) cultivars ‘Concord’, ‘Niagara’, ‘Catawba’ and ‘Delaware’. On interspecific hybrid ( Vitis sp .) and Vitis vinifera L. cultivars, E. comes was largely absent, and 97–100% of leafhoppers collected were 2 cryptic species, E. bistrata McAtee and E. vitifex Fitch. On the native American variety ‘Elvira’, a V. labrusca X V riparia Michaux hybrid, field populations were 24% E. comes and 74% the E. bistrata/vitifex complex. E. vitis (Harris), E. tricinta Fitch, and E. vulnerata Fitch were also present in commercial grapes, but never exceeded 20% of the populations sampled. Populations on wild V. riparia adjacent to vineyards were comprised of 24% E. comes , 47% E. histrata/vitifex , 19% E. vitis , and 10% E. tricinta . Dissection revealed that proportions of E. bistrata and E. vitifex in field collections, varied from 97% E. bistrata to 61% E. vitifex . Oviposition of E. comes and E. bistrata on V. vinifera , interspecific hybrid, and native American cultivars was compared in greenhouse choice tests and field no-choice tests. In choice tests, E. comes laid more eggs on Concord and Elvira than on the interspecific hybrid ‘Seyval blanc’, or the V. vinifera cultivar ‘White Riesling’. E. bistrata did not oviposit on Concord when paired with either Elvira, Seyval blanc or White Riesling. When caged to grape leaves in no-choice tests, E. comes laid the most eggs on native American cultivars and the fewest on V. vinifera and interspecific hybrids; E. bistrata laid the most eggs on hybrid and V. vinifera cultivars, and very few eggs on three native American cultivars. These results show that E. bistrata and E. vitifex are the principal pest species on V. vinifera and many interspecific hybrid cultivars in New York, and that E. comes is the principal leafhopper pest on native American V. labrusca cultivars.

799 PB 077 SUSCEPTIBILITY OF AMERICAN, EUROPEAN, AND INTERSPECIFIC HYBRID GRAPE CULTIVARS TO THE FUNGUS SEPTORIA AMPELINA

European Vitis vinifera L. (four cultivars); interspecific hybrid (seven cultivars); and American V. aestivalis Michx. (one cultivar), V. labrusca L. (three cultivars), and V. rotundifolia Michx. (two cultivars) grapevines were tested for susceptibility to Septoria leaf spot disease. V. rotundifolia cultivars Cowart and Fry exhibited hypersensitive-type resistance. All other American, European, and hybrid cultivars tested were susceptible with varying levels of disease severity. Cultivars with little (e.g. interspecific hybrid) or no (e.g. European) V. labrusca L. heritage were more susceptible to Septoria leaf spot than American V. labrusca cultivars.

Susceptibility of American, European, and Interspecific Hybrid Grape Cultivars to the Fungus Septoria ampelina

European Vitis vinifera L. (four cultivars); interspecific hybrid (seven cultivars); and American V. aestivalis Michx. (one cultivar), V. labrusca L. (three cultivars), and V. rotundifolia Michx. (two cultivars) grapevines were tested for susceptibility to septoria leaf spot disease. V. rotundifolia cultivars Cowart and Fry exhibited hypersensitive-type resistance. All other American, European, and hybrid cultivars tested were susceptible with varying levels of disease severity. Cultivars with little (e.g., interspecific hybrid) or no (e.g., European) V. labrusca L. heritage were more susceptible to septoria leaf spot than American V. labrusca cultivars.

Caftaric and coutaric acids in fruit of Vitis

The contents of trans and cis caftaric and coutaric acids were determined by HPLC under conditions fully protecting against oxidation in berry juices from five non- Vitis species, 28 Vitis species, 20 white and 17 red Vitis vinifera cultivars, six Vitis labrusca cultivars and 11 other varieties. These components appear to be genetically determined to a considerable degree. Replicate samples of the same variety from different sources generally gave similar composition. The compounds were absent from or present only in trace amounts in Vitis rotundifolia and four (of five) non- Vitis species. Other Vitis species all contained them but the content ranged from 5 mg/1 to 1350 mg/1 of caftaric and from a trace to 340 mg/1 of coutaric acid. Cultivars of Vitis vinifera did not differ appreciably whether white or red berries were involved, but ranged from 16 to 430 mg/1 of trans-caftaric acid, averaging 145 mg/1. Vitis labrusca and its cultivars averaged notably higher and hybrids were generally intermediate with their parent species. The cis percentage increased, particularly for coutaric with the varieties arranged in order of decreasing caftaric concentration, but appeared to reflect environmental rather than genetic influences. The proportion of coutaric acid, however, appeared quite variable (3-33 % of the caftaric content in the vinifera cultivars) by variety and was apparently genetically controlled.

Volatile Constituents from Concord, Niagara (Vitis labrusca, L.) and Elvira (V. labrusca, L. x V. riparia, M.) Grapes

By means of combined vacuum distillation and extraction, volatile constituents were separated from the berries of Concord, Niagara (V. labrusca, L.) and Elvira (V. labrusca, L. ×V. riparia, M.) grapevines. Using the combination of adsorption chromatography on silica gel and coupled gas chromatography-mass spectrometry, 25 acids, 19 alcohols, 22 carbonyls, 63 esters, 6 hydrocarbons and 10 compounds of miscellaneous structures were identified. Numerically prevailing were unsaturated esters such as ethyl trans-2 hexenoate, ethyl trans-2-octenoate, ethyl cis-4-decenoate, ethyl trans-2-decenoate, and especially the isomer ethyl 2,4-decadienoates were found to contribute to the inherent sweet-fruity odour of the labrusca cultivars investigated. 2,5-dimethyl-4-methoxy-3(2H)-furanone may be responsible for the caramel-like undertone in the aroma fraction obtained from Concord and Niagara grapes. Despite the preparative gas chromatographic enrichment of this fraction, the structure(s) of the substance(s), which might be responsible for this undesirable sensory impression, could not be determined.The composition of volatile substances in the cultivars studied differed only quantitatively and not qualitatively. Quantitative gas chromatography showed the level of volatile compounds in Elvira grapes to be lower than the labrusca cultivars. Methyl anthranilate, methyl and ethyl 3-hydroxybutanoate, ethyl 2-butenoate and 2,5-dimethyl-4-methoxy-3(2H)-furanone, were all detected in high amounts in Concord and Niagara grapes, but were only found in trace amounts in Elvira grapes.

Changes in Free Amino Acid and Total Nitrogen Concentrations During Maturation of Muscadine Grapes (V. rotundifolia)

ABSTRACTFree amino acids, ammonia and total nitrogen were followed during maturation of berries of Carlos and Noble muscadine grapes (V. rotundifolia). Chemical analysis was done on deseeded berries. Ammonia decreased in the berries of both cultivars during maturation. Total nitrogen content fluctuated and was not significantly correlated with maturity in either cultivar. Threonine (THR) and histidine + gamma aminobutyric acid (HIS + GABA) were the predominant free amino acids in both cultivars at an immature berry stage. At full berry maturity, arginine (ARG) was the predominant amino acid in Carlos, having increased over 100‐fold during the sampling period while ARG, alanine (ALA), THR, and HIS + GABA accounted for 72.3% of the total free amino acids. ALA was the predominant free amino acid in mature berries of Noble and accounted for 30.4% of the total free amino acids. Of the additional cultivars sampled only at their normal harvest date, berries of Pride, Magnolia and Regale contained nearly equal amounts of ARG and ALA as the predominant amino acids. Mature Dixie berries had twice as much ALA (29.8%) as ARG (12.8%). In general, the free amino acids in berries of muscadine grapes were found in concentrations similar to those reported in the literature for V. vinifera and V. labrusca cultivars. However, the large increase in proline concentration reported to occur during maturation of berries of V. vinifera cultivars was not found in any of the muscadine cultivars examined.