Vinifera Cultivars Research Articles

Histopathological study of resistant (Vitis labrusca L.) and susceptible (Vitis vinifera L.) cultivars of grapevine to the infection by downy mildew

ABSTRACT Plasmopara viticola (Berk. & M. A. Curtis) Berl & de Toni is a biotrophic oomycete responsible for downy mildew on grapevine. This study aimed to compare the development of P. viticola between a resistant interspecific hybrid of Vitis labrusca (‘Ives’, synonym ‘Bordô’), and a susceptible V. vinifera (‘Cabernet Sauvignon’) cultivars at different times after inoculation with the pathogen. The host leaf tissues were analysed at 0, 6, 12, 24, 48, 72, 96 and 120-h post-inoculation (hpi), by means of light optical microscopy and scanning electronic microscope (SEM). Light optical microscopy was used to analyse the pathogen development in the mesophyll intercellular spaces, as well as the histochemical changes occurring at host level during the infection. Structural differences were observed in stomata, and in the shape of mesophyll cells in the resistant cultivar after infection. SEM analysis showed differences in the pathogen development between both cultivars. All the stages of pathogen development were observed on the leaf surface of cv. ‘Cabernet Sauvignon’, but not in the cv. ‘Ives’. The results showed that cv. ‘Ives’ and ‘Cabernet Sauvignon’ display structural and histochemical differences to the downy mildew infection. Implications of these differences to the plant–pathogen interactions are discussed.

A continuum of stomatal responses to water deficits among 17 wine grape cultivars (Vitis vinifera).

Vitis vinifera L. cultivars have been previously classified as isohydric, near-isohydric, anisohydric or isohydrodynamic, depending on the study. To test the hypothesis that V. vinifera cultivars' stomatal behaviour can be separated into distinct classes, 17 cultivars grown in a replicated field trial were subjected to three irrigation treatments to manipulate vine water status across multiple years. Predawn (ΨPD) and midday (Ψl) leaf water potential and midday stomatal conductance (gs) were measured regularly throughout several seasons. The relationship of gs to Ψl was best modelled as a sigmoidal function and maximum stomatal conductance (gmax), water status at the onset of stomatal closure (Ψl95), sensitivity of closure (gsensitivity) and water status at the end of closure (Ψl25) were compared. There were no significant differences in gmax among cultivars. Cultivar-specific responses of gs to Ψl were broadly distributed along a continuum based on the relationship between Ψl95 and gsensitivity. Season-long cultivar mean Ψl values were positively related to Ψl25. In general, cultivars responded similarly to one another at high and low water status, but their stomatal behaviour differed at moderate water deficits. The results show that V. vinifera cultivars possess both iso- and anisohydric stomatal behaviours that depend on the intensity of water deficits, and call into question previous classifications assuming a single behaviour.

Increase in seed tannin extractability and oxidation using a freeze-thaw treatment in cool-climate grown red (Vitis vinifera L.) cultivars

Grape seed maturation involves the gradual oxidation of tannins, decreasing excessive bitterness and astringency in wine. In cool climates, this process is limited by the short growing season, affecting wine quality. A “freeze-thaw” treatment on seeds of red vinifera cultivars at veraison and harvest was used to evaluate the effect of oxidation and extractability on seed phenolic fractions. Freezing increased the extraction of total phenolics and o-diphenols quantified from fractionation (fraction 1, vacuolar tannins; fraction 2, hydrogen bonded tannins; fraction 3, covalently bonded tannins), especially at harvest. Despite this, colorimetry, microscopy, oxidation reactivity index (ORI), and correlations between the color index and fractions indicated that freezing disrupted vacuole integrity, enhancing oxidation in the seed coat. In conclusion, vacuolar tannins (which are the main seed phenolics extracted during fermentation) were highly correlated with seed color change, potentially providing information for winemaking in cool climate regions.

Understanding the phyllosphere microbiome assemblage in grape species (Vitaceae) with amplicon sequence data structures

Impacts of plant genotype on microbial assemblage in the phyllosphere (above-ground parts of plants, which predominantly consists of the set of photosynthetic leaves) of Vitis vinifera cultivars have been studied previously but the impact of grape species (under the grape family Vitaceae) was never investigated. Considering the fact, that the phyllosphere microbiome may have profound effects on host plant health and its performance traits, studying the impact of grape species in microbial taxa structuring in the phyllosphere could be of crucial importance. We performed 16S and ITS profiling (for bacteria and fungi respectively) to access genus level characterization of the microflora present in the leaf phyllosphere of five species within this plant family, sampled in two successive years from the repository situated in the Mediterranean. We also performed α and β-diversity analyses with robust statistical estimates to test the impacts of grape species and growing year, over a two-year period. Our results indicated the presence of complex microbial diversity and assemblages in the phyllosphere with a significant effect of both factors (grape species and growing year), the latter effect is being more pronounced. We also compared separate normalization methods for high-throughput microbiome data-sets followed by differential taxa abundance analyses. The results suggested the predominance of a particular normalization method over others. This also indicated the need for more robust normalization methods to study the differential taxa abundance among groups in microbiome research.

Relationship Between Hot Water Treatment (HWT) and Vitality Criteria On Dormant Cuttings of Vitis Vinifera Cultivars and Rootstocks

The experiment was conducted during 2016–2017 on Vitis vinifera cultivars (cv.) ‘Superior Seedless’, ‘Razaki’, ‘Crimson Seedless’, ‘Sultana’, ‘Royal’, and American rootstocks (41B, 1103P, 1616C, Ramsey, 5BB) at Department of Horticulture, Agriculture Faculty, Ege University, Turkey. This study was designed to investigate the effects of HWT on the quality of hard wood cuttings following the treatment. The hard wood cuttings that were hot water treated at 50 °C for 30 min which is the most common protocol against Agrobacterium vitis used worldwide. After HWT, cuttings (ungrafted) were planted in black polythene bags for rooting in greenhouse conditions. In this experiment, the effects of HWT on cuttings and root distribution (0–4 scala), root number, root length (cm), shoot length (cm), sprouting rate (%), rooting rate (%), fresh and dry root weight (g) were investigated. HWT was found to have variable effects on different characteristics of cultivar and rootstock cuttings. 41B saplings were negative affected from HWT for root distribution (0–4 scala), root number, shoot length (cm), sprouting rate (%), fresh and dry root weight (g). The HWT for 41B rootstock cuttings should be done carefully. ‘Superior Seedless’, ‘Razaki’ and ‘Royal’ were affected positively by HWT compared to non-HWT group cuttings for some criterians.

Nonlinear Behavior of Protein and Tannin in Wine Produced by Cofermentation of an Interspecific Hybrid (Vitis spp.) and vinifera Cultivar

Wines produced from red interspecific hybrid grape cultivars (Vitis spp.) typically have lower tannin concentrations than wines produced from vinifera cultivars, which can be attributed to the lower concentration of tannins and higher concentration of tannin-binding proteins of interspecific cultivars. Tannin in wines produced from hybrid cultivars may be increased by blending hybrids with vinifera. We hypothesized that blending of grapes prior to fermentation (cofermentation) would result in final wine tannin concentrations lower than those predicted from the individual components due to protein-tannin binding, but that this effect would be absent from monovarietal wines blended postfermentation. To evaluate this hypothesis, a high tannin V. vinifera cultivar (Cabernet Sauvignon) was blended with an interspecific hybrid (Marquette) at different ratios either before (cofermentation) or after fermentation over a two-year period. The tannin and protein concentrations of the wines were measured by methyl cellulose precipitation assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively. Tannin and protein concentrations in blended wines were compared to values predicted from the linear combination of the two monovarietal wines. Cofermented blends with a high proportion of Marquette had up to 25% lower tannin than predicted, but observed and predicted tannin concentrations did not differ for most cofermentations and postfermentation blends. However, protein concentrations for many of the blends—especially from cofermentation—were lower than predicted values (>50% in some cases). Loss of protein due to adsorption to tannin was well modeled by a Freundlich adsorption isotherm.

Polyphenolic compounds and antioxidants of skin and berry grapes of Greek Vitis vinifera cultivars in relation to climate conditions

The Greek vineyard is home to many minor, indigenous grape cultivar whose diverse polyphenolic content has remained largely unexploited. The study aimed at assaying and assessing the polyphenolic content and antioxidant capacity of: (a) five obscure cultivars; (b) Six biotypes of cultivar ‘Liatiko’; (c) Five prominent cultivars; and (d) three French varieties included for comparison reasons. Results revealed all samples exhibiting high polyphenol content and antioxidant capacity levels. ‘Vertzami’ recorded the highest concentrations in berry skins total anthocyanins, flavanols, flavonols, antioxidant capacity. ‘Mandilaria’ scored the highest value in seed total flavanols compared to all biotypes and cultivars. All ‘Liatiko’ biotypes scored the highest concentrations in seed total flavonoids and flavonols. ‘Liatiko’ and its biotypes exhibited different polyphenolic profiles between them. Owing to the climate change, those indigenous varieties’ substantial polyphenol amounts, and the differences between biotypes, will allow viticulturists to select the varieties/biotypes most appropriate for obtaining higher quality products.

Rpv3\u20131 mediated resistance to grapevine downy mildew is associated with specific host transcriptional responses and the accumulation of stilbenes

BackgroundEuropean grapevine cultivars (Vitis vinifera spp.) are highly susceptible to the downy mildew pathogen Plasmopara viticola. Breeding of resistant V. vinifera cultivars is a promising strategy to reduce the impact of disease management. Most cultivars that have been bred for resistance to downy mildew, rely on resistance mediated by the Rpv3 (Resistance toP.viticola) locus. However, despite the extensive use of this locus, little is known about the mechanism of Rpv3-mediated resistance.ResultsIn this study, Rpv3-mediated defense responses were investigated in Rpv3+ and Rpv3ˉ grapevine cultivars following inoculation with two distinct P. viticola isolates avrRpv3+ and avrRpv3ˉ, with the latter being able to overcome Rpv3 resistance. Based on comparative microscopic, metabolomic and transcriptomic analyses, our results show that the Rpv3–1-mediated resistance is associated with a defense mechanism that triggers synthesis of fungi-toxic stilbenes and programmed cell death (PCD), resulting in reduced but not suppressed pathogen growth and development. Functional annotation of the encoded protein sequence of genes significantly upregulated during the Rpv3–1-mediated defense response revealed putative roles in pathogen recognition, signal transduction and defense responses.ConclusionThis study used histochemical, transcriptomic and metabolomic analyses of Rpv3+ and susceptible cultivars inoculated with avirulent and virulent P. viticola isolates to investigate mechanism underlying the Rpv3–1-mediated resistance response. We demonstrated a strong correlation between the expressions of stilbene biosynthesis related genes, the accumulation of fungi-toxic stilbenes, pathogen growth inhibition and PCD.

Field performance of five white Pilzwiderstandsfahige (PIWI) cultivars in the south of Brazil

Southern Brazil is the largest grape-producing region in the country. It is characterized by the production of labrusca grapes, because of the difficulty of growing Vitis vinifera. This can be explained by the high occurrence of fungal diseases, especially downy mildew, which is favored by the environmental conditions (high temperatures, relative humidity and rainfall). Pilzwiderstandsfahige (PIWI) are a group of wine-grape cultivars similar to V. vinifera but with resistance to downy and powdery mildew. These cultivars open the possibility of reducing production cost and agrochemical sprays for viticulture in Brazil. In order to achieve this objective, studies related to phenological, productive and qualitative characteristics are necessary. A PIWI cultivar trial was established in 2015, in the city of Videira, Santa Catarina State, Brazil, with five white cultivars. The vines were trained in vertical shoot position (VSP) trellis and pruned in double cordons. The studied cultivars were ‘Felicia’, ‘Calardis Blanc’, ‘Helios’, ‘Bronner’ and ‘Aromera’, grafted on ‘Paulsen 1103’. The variables evaluated were phenology, incidence of downy mildew, yield, number of clusters, average cluster weight, total soluble solids, pH and total titratable acidity. In terms of productivity, the outstanding cultivars were ‘Felicia’ and ‘Calardis Blanc’, with yields above the traditional V. vinifera cultivars. ‘Felicia’ was the earliest cultivar and produced the heaviest clusters. ‘Calardis Blanc’ presented the largest number of clusters, and ‘Aromera’ was the latest cultivar. Soluble solids contents, pH and acidity were adequate in all cultivars. In general, all tested cultivars showed good potential for the studied region.

New cold-tolerant grapevine cultivars for red wines

Krasnodar Region is the main region of industrial viticulture in the Russian Federation. Natural conditions allow high-quality cultivars to be grown there; however, in certain years, the impact of low-temperature stresses of the winter period, summer droughts and diseases limit the stable high-yield production of Vitis vinifera. Breeding of grapevine cultivars for high-quality winemaking and adaptability to local agro-climatic conditions is carried out at the North-Caucasian Federal Scientific Center of Horticulture, Viticulture and Wine-making. Interspecific hybrids are used as donors of resistance in crosses with high-quality V. vinifera cultivars. New hybrids were studied by agrobiological research, and wines and must from grapes were studied by organoleptic evaluation, physico-chemical and biological indicators. Highly adaptive cultivars ‘Dmitriy’, ‘Kurchanskiy’ and ‘Vladimir’ for red wines were selected as a result. They are tolerant to low temperatures in winter, down to -27°C. The cultivars have high levels of resistance to the main pathogens (mildew, botrytis), and ‘Dmitriy’ is resistant to root phylloxera. Yields of ‘Kurchanskiy’ and ‘Vladimir’ were 12-13 t ha(‑1), and that of ‘Dmitriy’ was 14-15 t ha(‑1). These cultivars combine adaptability to the unstable conditions of the south of Russia with high-quality wine production. ‘Vladimir’ is distinguished by the total amount of phenolic substances (average 3603 mg L(‑1)). Samples of wine from ‘Kurchanskiy’ and ‘Dmitriy’ show high accumulation of anthocyanins (more than 1000 mg L(‑1)). The cultivars are now being tested by governmental authorities.

Phenology and thermal requirements of disease-resistant genotypes (PIWI) grown in the Goethe Grape Valley region of Brazil

The Goethe Grape Valley (GGV) is a traditional southern Brazilian region for grape and wine production, mainly planted with hybrid vines. High temperatures and rainfall conditions hamper the cultivation of Vitis vinifera cultivars susceptible to disease, especially Plasmopara viticola. New PIWI (from the German word ‘Pilzwiderstandsfahige’) genotypes of V. vinifera with resistance to P. viticola are under evaluation in this region. The aim of this work was to characterize the phenology and thermal requirements of PIWI genotypes grown in the GGV. The experiment was carried out in an experimental vineyard (28°32’S 49°19’W, altitude 60 m a.s.l.), established in 2016, and evaluations were done for the 2018 vintage. The evaluated PIWI cultivars were ‘Aromera’, ‘Baron’, ‘Calardis blanc’ and ‘Felicia’. Minimum and maximum air temperatures were recorded daily, using 10°C as the low temperature threshold, 25°C as the optimum temperature for development, and 35°C as the upper temperature threshold of development. The evaluated phenological stages were budbreak to flowering, flowering to veraison and veraison to maturity. The total thermal requirement mean was 1360°C day; ‘Felicia’ showed the lowest thermal requirement (1260°C day), which contrasted with ‘Aromera’, which presented the highest thermal requirement (1454°C day). ‘Baron’ and ‘Calardis blanc’ needed 1337 and 1391°C day, respectively, to reach maturity. From budbreak to flowering, the average thermal requirement was 229°C day, from flowering to veraison the mean was 679°C day, and from veraison to maturity the mean was 452°C day. The four evaluated cultivars exhibited adaptive development in the field with thermal requirements compatible with the region of GGV. The results also revealed the lower thermal requirement, and consequently shorter cycle, for ‘Felicia’, as well as the greater thermal requirement of ‘Aromera’.

Durable powdery mildew resistance in grapevines: myth or reality

Grape powdery mildew (PM) is an economically important disease worldwide, and necessitates high input of fungicides for successful grape production. Development of cultivars that carry resistance from multiple backgrounds is an important strategy to obtain durable resistance in the field. This strategy requires a) the identification of sources of resistance and marker development to track those resistances, b) characterization of the mechanisms of resistance, c) marker-assisted breeding to introduce the selected loci into elite cultivars, and, finally, d) understanding of pathogen biology and responses to different resistance sources. We have identified and tagged novel sources of genetic resistance from eight genetic backgrounds, including Muscadinia rotundifolia, two different Chinese species (Vitis piasezkii and Vitis romanetii), a wide array of Vitis vinifera cultivars and wild forms of V. vinifera subsp. sylvestris from Asia. Molecular markers that are tightly linked to different loci are used at the early stage to select seedlings that carry resistance loci. PM resistance from two or more genetic backgrounds is combined in multiple steps, while maintaining high fruit-quality attributes and other important horticultural traits. Resistance is confirmed by careful evaluation for disease development in the field, the greenhouse or by in-vitro assay. Multipronged testing of seedling plants for resistance allows better assessment of pathogen biology and interaction with different resistance loci and allows us to make decisions about combining resistance loci. Results will be presented with elucidation of the mechanism of resistance from different backgrounds, specificity to different isolates and the effectiveness of molecular markers in the breeding program.

Early detection of Plasmopara viticola-infected leaves through FT-ICR-MS metabolic profiling

Grapevine (Vitis vinifera L.) is one of the most important crops in the world. Domesticated V. vinifera cultivars frequently used for wine production are highly susceptible to different diseases, including downy mildew, one of the most destructive vineyard diseases, caused by Plasmopara viticola. Downy mildew affects all green parts of the vine, causing yield reduction and significant production losses. To cope with this threat, the application of chemical products is currently the mainly strategy, with severe environmental and economic costs. The development of alternative sustainable disease-control strategies is crucial. Early detection of infected plants is not easy, since observable disease symptoms normally appear 7-10 days after pathogen inoculation. Thus, the development of early detection techniques is very important to control downy mildew spread. In the present work, we followed an untargeted metabolomics approach using Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR-MS) to analyse the chemical profile of infected and non-infected grapevine leaves. Chemical formulas were used to build Van Krevelen diagrams and compositional space plots, which do not require full metabolite identification and provide an easy screening method. Based only on the chemical profile and representation plots, we were able to discriminate between infected and non-infected grapevine leaves as soon as 24 h post-inoculation. Moreover, our results show that lipids, carbohydrates and polyketides are the most altered metabolite groups in P. viticola-infected plants when compared with control samples.

Evidence for sexual reproduction and fertile oospore production byPlasmopara viticolaon the leaves of partially resistant grapevine cultivars

Downy mildew, caused by Plasmopara viticola, is a highly destructive disease of grapevine. In recent decades, European breeding programs for disease resistance have led to the creation of new cultivars resistant to downy mildew. This resistance limits mycelium growth and the sporulation of P. viticola, thereby decreasing disease epidemics due to the asexual reproduction of the pathogen. However, we still lack biological insight into the effects of partial host resistance on pathogen survival during the sexual stage of its lifecycle. We present here the results of a two-year experiment in which we assessed the production of sexual forms of P. viticola (oospores) and the success of subsequent infections on resistant cultivars with the Rpv1 and Rpv3 loci. We found that disease resistance had little effect on the sexual cycle of the pathogen. Plasmopara viticola produced four times more oospores on susceptible Vitis vinifera cultivars than on disease-resistant cultivars. Macrosporangia resulting from the germination of oospores were found on both resistant and susceptible genotypes, and were produced in surprisingly large numbers on some Rpv1 genotypes. Rates of primary contamination due to macrosporangia were lower on Rpv3 than on conventional cultivars, but higher on Rpv1 genotypes. Thus, P. viticola can complete its lifecycle (both asexual and sexual phases) on partially resistant grapevine cultivars. The maintenance of downy mildew populations from one year to the next presents a significant challenge to the sustainability of genetic resistance in grapevine.

Whole-genome sequencing and gene annotation of Georgian grape cultivars

The genomes of four Georgian grape cultivars, ‘Chkhaveri’, ‘Saperavi’, ‘Meskhetian green’, and ‘Rkatsiteli’, belonging to different haplogroups, were resequenced. Shotgun genomic libraries of grape cultivars were sequenced on an Illumina HiSeq. The sequences of all 19 chromosomes of the four Georgian grape cultivars were determined by resequencing using ‘Pinot noir’ as a reference genome. Annotation of chromosomal DNA of Georgian grape revealed 17,409 candidate genes in ‘Chkhaveri’, 17,021 in ‘Saperavi’, 18,355 in ‘Meskhetian green’ and 13,960 in ‘Rkatsiteli’. Among them, 106 predicted genes and 43 pseudogenes of terpene synthase (TPS) and 44 candidate genes of stilbene synthase (STS) were found in all studied Georgian cultivars. Several additional TPS and STS genes not present in the reference ‘Pinot noir’ genome were detected. This is the first attempt at a comparative whole-genome analysis of different haplogroups of Vitis vinifera cultivars.

Geographical origin of Vitis vinifera cv. Cannonau established by the index of bioaccumulation and translocation coefficients.

Geochemical fingerprints in grape require an identification of major and trace elements that show correlations between concentrations in soil and in plant tissues: these correlations are relevant to discriminate grapes according to geographical origin. The Vitis vinifera cultivar Cannonau is used to produce the renowned Italian controlled designation of origin (DOC) wine "Cannonau" from Sardinia. Two Cannonau vineyards located in Sardinia Region were studied to establish the relationship between geochemical features of vineyard soil and chemical composition of leaves and grape berries. Major and trace elements were determined by X-ray fluorescence and inductively coupled plasma-mass spectrometry in soil, leaf, and grape berry samples. The index of bioaccumulation and the translocation coefficients were also calculated for all elements. Data from the two study areas were compared by a non-parametric test and multivariate statistics (principal component analysis). The results showed a specific assimilation of these elements in leaf and grape berry from vine in two different soils. Moreover, geochemical characterization and statistical analysis enabled to discriminate the cultivar "Cannonau" according to geographical origin. The results showed that the elements that could establish a reliable correlation between the soil vineyard and leaves and grape berries from the two study areas were B, Sr, and Zr. These elements may therefore be used as geochemical fingerprints to identify the geographic origin of V. vinifera cv. Cannonau in the two study areas.

Timing and Intensity of Grapevine Defoliation: An Extensive Overview on Five Cultivars in Switzerland

This article synthetizes observations from five experiments and reports on the effects of timing and intensity of defoliation on the white and red Vitis vinifera cultivars Pinot noir, Gamay, Merlot, Chasselas, and Doral. Intensive defoliation (removal of six basal leaves + six lateral shoots per shoot) was completed at three developmental stages of the grapevine: preflowering, flowering, and bunch closure. Preflowering defoliation had tremendous consequences on vine agronomic performance, mainly to the detriment of berry set; the yield was highly affected by preflowering defoliation (approximately -35% of that from vines with no defoliation). The intensity of defoliation allowed its impact on the yield to be modulated. The intensity of defoliation also had a positive impact against millerandage, sunburn symptoms, and Botrytis cinerea development. The berry skin thickness doubled and the polyphenol concentration increased significantly with preflowering defoliation. Due to preflowering defoliation, the red wines were often preferred for their color and mouthfeel. However, this practice had a negligible impact on white wine composition. Regardless, preflowering defoliation did not negatively impact wine parameters. In the context of this study, preflowering defoliation has potential to reduce vigor and control high production potential. Preflowering defoliation also represents a prophylactic solution to reduce both chemical applications and cluster-thinning costs.

Regeneration of plants from embryogenic callus-derived protoplasts of Garganega and Sangiovese grapevine (Vitis vinifera L.) cultivars

Protoplasts are useful research tools for basic and applied plant science, but the regeneration of whole plants from protoplasts is challenging in most of agronomically important crops, including grapevine (Vitis vinifera L.). Here we describe an efficient protocol for the induction of embryogenic callus, the isolation of protoplasts, and the regeneration of whole grapevine plants in two Italian grapevine cultivars. Embryogenic callus was induced successfully from stamens collected from immature flowers. Isolated protoplasts were tested to confirm their viability and then cultivated using the disc-culture method, at a density of 1 × 105 protoplasts/mL in solid Nitsch’s medium supplemented with 2 mg/L 1-naphthaleneacetic acid and 0.5 mg/L 6-benzylaminopurine. After 3–4 months, the protoplasts of both cultivars regenerated with similar efficiency into cotyledonal-stage somatic embryos. The somatic embryos were transferred to solid Nitsch’s medium supplemented with 30 g/L sucrose and 2 g/L gellan gum, and were maintained in the dark for 4 weeks. This step was necessary for the embryo to complete germination, allowing subsequent shoot elongation in response to light on a medium with 4 µM 6-benzylaminopurine. Then root elongation occurred after transferring on a medium with 0.5 µM 1-naphthaleneacetic. After ~ 6 months from the isolation of protoplasts, normal plants were regenerated, which were moved to the greenhouse. The protoplasts could also be transfected using the polyethylene glycol method, as confirmed using a plasmid carrying the yellow florescent protein marker gene. The new method is therefore compatible with biotechnological applications such as gene transfer and genome editing. This study reports an improved protocol for embryogenic callus induction, protoplast isolation and whole plant regeneration of two Vitis vinifera cultivars. Protoplasts showed high transfection efficiency.

Assessment of Pierce's disease susceptibility in Vitis vinifera cultivars with different pedigrees

Pierce's disease (PD) of grapevine is caused by the bacterium Xylella fastidiosa. In this study, an integrated approach was applied to assess PD susceptibility among different Vitis vinifera cultivars that incorporated disease severity, bacterial pathogen abundance and loss of stem xylem hydraulic conductivity. It was hypothesized that levels of PD susceptibility in V. vinifera can be attributed in part to the host anatomical features that are shaped by its pedigree background. Two popular wine grape cultivars were initially selected from the occidentalis group, Merlot and Cabernet Sauvignon, and one from the orientalis group, Thompson Seedless. The more recently bred table grape cultivar Scarlet Royal, that has mixed pedigree parentage, was also included. PD susceptibility was compared to the known PD resistant b43‐17 V. arizonica/candicans wild grape species from North America. The data indicated that Thompson Seedless was ranked as the most susceptible to PD because it significantly exhibited the most severe disease symptoms at 12 weeks post‐inoculation and hosted the highest X. fastidiosa titre of the cultivars, and lost over 90% of its stem hydraulic conductivity. In contrast, the other three cultivars displayed less susceptibility to PD. The way in which the xylem anatomy could impact PD susceptibility in V. vinifera cultivars is discussed, together with how grape pedigrees and their cognate centre of domestication may have influenced xylem anatomical features. This work provides a reference framework to further test the hypothesis that V. vinifera cultivars with wide xylem vessels may be more prone to PD decline.

Effects of Two Different Irrigation Systems on the Amino Acid Concentrations, Volatile Composition and Sensory Profiles of Godello Musts and Wines.

The concentrations of amino acids and volatile compounds of a given grapevine cultivar may be modified by climate variability between years and by management practices, such as irrigation, that may alter the typicality of its wines. The current study aimed at assessing the amino acid profile of musts and wines, volatile composition and sensory profile of wines from Vitis vinifera (L.) cultivar Godello under rain-fed and two drip irrigation systems (above, drip irrigation (DI), and under the soil surface, subsurface drip irrigation (SDI)) over three consecutive years. Irrigation tended to increase must and wine total acidity; however, it did not alter must amino acid concentrations significantly. Irrigation reduced the concentrations of acetaldehyde and methanol in Godello wines. Moreover, irrigation tended to decrease the concentrations of compounds giving fruity aromas, such as acetaldehyde (by 31% in SDI) and isoamyl acetate (by 21% in SDI), when compared to rain-fed conditions. Sensory analysis revealed slight differences between treatments. Rain-fed and SDI were the treatments showing the greatest differences. Weather conditions affected more must and wine composition than in-season effects caused by irrigation.