Vinifera Genotypes Research Articles

Comparative analysis of stomatal characteristics and Erysiphe necator (Schw.) Burrill resistance in diverse Vitis sp.

Powdery mildew caused by Erysiphe necator poses a major challenge for grapevine cultivation. This study investigates how stomatal and structural traits influence resistance to this pathogen across diverse Vitis genotypes. Microscopic analysis revealed significant variations in stomatal characteristics. The sunken stomata were observed in V. parviflora, V. jacquemontii, V. rupestris x V. berlandieri (110 Richter) and V. rupestris (St. George) with lower stomatal density. Genotypes with raised stomata had larger stomatal complex areas. Following inoculation with E. necator (accession No. 52218), the Vitis genotypes showed a distinct resistance response. Susceptible V. vinifera genotypes had high pathogen penetration rates, with 71 % of infection attempts forming haustoria. In contrast, V. parviflora, V. jacquemontii, and hybrids such as V. rupestris x V. berlandieri and V. riparia x V. cinerea exhibited programmed cell death (PCD)-mediated resistance, arresting up to 55 per cent of penetration attempts limiting hyphal growth. Cryo-SEM images further indicated sparse fungal growth on the resistant genotypes. The genotype V. parviflora possessed dense trichomes and long wax stripes along the epidermal cells covering leaf veins on the adaxial leaf surface, thus causing a physical barrier against the pathogen. Comparative analyses showed that callose deposition and epicuticular wax significantly contributed to early-stage pathogen defence, while reactive oxygen species and rapid PCD activation triggered hypersensitive responses, enhancing wax deposition and active PCD responses are critical for Vitis sp. resistance to powdery mildew, offering valuable insights for breeding programmes.

Susceptibility to flavescence dorée of different Vitis vinifera genotypes from north‐western Italy

AbstractThe aim of this work was to evaluate the susceptibility to flavescence dorée (FD) of 12 Vitis vinifera cultivars grown in Piedmont, and representative of the wine‐making tradition of this area. The experiments were conducted under controlled conditions to ensure constant infection pressure. Test plants were ex vitro potted vines, singly inoculated with four Scaphoideus titanus infected by FD‐C phytoplasma (FDp), under greenhouse conditions. Vines were tested for FDp at 5 and 8 weeks postinoculation (wpi) and the phytoplasma load was measured in leaves and roots at 8 wpi. Within the 14 V. vinifera accessions (belonging to 12 cultivars), three susceptibility clusters were identified. Cultivars within the low susceptibility group showed low phytoplasma loads and low percentages of infected plants, suggesting a tolerant behaviour. To confirm these results, four Vitis cultivars, representing extremes of FD susceptibility from low to high, were grafted onto Kober 5BB rootstocks and inoculated with laboratory‐infected S. titanus, under semi‐field conditions. The transmission experiments onto grafted cuttings confirmed that susceptibility to the disease depends on the scion genotype. The data indicated that none of the tested V. vinifera genotypes are resistant to FD, although some cultivars with low susceptibility are available, and can be explored for identifying genetic traits involved in disease tolerance/resistance. Moreover, ranking Vitis genotypes for their susceptibility to FD is in itself a valuable tool to support vine growers in their decision management, by helping them to choose the most appropriate varieties according to their specific FD epidemiological contexts.

Prospecting for resistance of interspecific hybrids of Vitis spp. to Plasmopara viticola

In partnership with the University of California—UCDavis, this study intends to develop downy mildew-resistant grape cultivars with good agronomic traits. Hence, the goals of this research were to estimate the genetic parameters, via REML/BLUP, of variables related to downy mildew resistance in a population composed of 63 interspecific hybrids and to select promising clones on the basis of genotypic values for the breeding program of the grapevine. The experiment was conducted in randomized blocks with three replicates and one plant per plot. The evaluations were carried out in two different seasons and focused on determining disease severity. The severity data provided the basis for calculating the area under the disease progress curve (AUDPC) and the maximum severity (Smax). Differences in the severity of downy mildew symptoms were reported among the 63 genotypes of Vitis spp., such as immune individuals (score 0) and highly susceptible to the AUDPC (3146.67) and Smax (80.56) variables in the two seasons analyzed. The high genotype correlation seen for AUDPC (80.95%) and Smax (89.68%) suggests that the majority of genotypes had a similar response in terms of symptom severity in the two seasons evaluated. The greatest proportion of genetic variance was resulting from the effects of dominance, which corresponds to 244,165.9580 and 179.83, for AUDPC and Smax, respectively, suggesting that hybridizations are viable in the introgression of the resistance. Consequently, the values for individual heritability of the effects of dominance were greater (50.34 and 52.83%) for the AUDPC and Smax variables, respectively. It is thus recommended that the 20 most resistant genotypes, with lower genetic values for the two variables analyzed, be selected and crossed with Vitis vinifera genotypes to obtain resistant hybrids.

Photosynthetic Cost Associated With Induced Defense to Plasmopara viticola in Grapevine.

Downy mildew caused by Plasmopara viticola is one of the most destructive diseases of Vitis vinifera worldwide. Grapevine breeding programs have introgressed P. viticola-resistant traits into cultivated V. vinifera genotypes and launched interspecific hybrids with resistance against downy mildew. In general, pathogen infection affects primary metabolism, reduces plant growth and development and modifies the secondary metabolism toward defense responses, which are costly in terms of carbon production and utilization. The objective of this work was to evaluate the photosynthesis impairment by inducible defenses at the leaf level in V. vinifera cultivars resistant to P. viticola. Photosynthetic limitations imposed by P. viticola in susceptible and resistant grapevine cultivars were evaluated. Histochemical localization of hydrogen peroxide and superoxide and the activity of ascorbate peroxidase were assessed. Measurements of leaf gas exchange, chlorophyll fluorescence and the response of leaf CO2 assimilation to increasing air CO2 concentrations were taken, and photosynthetic limitations determined in cultivars Solaris (resistant) and Riesling (susceptible). The net photosynthetic rates were reduced (−25%) in inoculated Solaris plants even before the appearance of cell death-like hypersensitive reactions (“HR”). One day after “HR” visualization, the net photosynthetic rate of Solaris was reduced by 57% compared with healthy plants. A similar pattern was noticed in resistant Cabernet Blanc and Phoenix plants. While the susceptible cultivars did not show any variation in leaf gas exchange before the appearance of visual symptoms, drastic reductions in net photosynthetic rate and stomatal conductance were found in diseased plants 12 days after inoculation. Decreases in the maximum Rubisco carboxylation rate and photochemical impairment were noticed in Riesling after inoculation with P. viticola, which were not found in Solaris. Damage to the photochemical reactions of photosynthesis was likely associated with the oxidative burst found in resistant cultivars within the first 24 h after inoculation. Both chlorophyll degradation and stomatal closure were also noticed in the incompatible interaction. Taken together, our data clearly revealed that the defense response against P. viticola causes a photosynthetic cost to grapevines, which is not reversible even 12 days after the pathogen infection.

Transcriptional regulation of stilbene synthases in grapevine germplasm differentially susceptible to downy mildew

BackgroundTo limit the impact of the downy mildew disease of grapevine and reduce the need to recur to chemical treatments, an effective strategy might be recovering adaptive resistance traits in both cultivated and wild V. vinifera germplasm. Considering that stilbenes represent the most important class of phytoalexins in the Vitaceae, the constitutive expression and transcriptional activation of all the functional members of the stilbene synthase gene family were analysed in a group of nine grapevine genotypes following artificial infection with the oomycete Plasmopara viticola, the causal agent of the disease. In addition, in the same genotypes we analyzed the expression of genes encoding for two transcription factors involved in the transcriptional regulation of the stilbene synthase genes, namely VvMYB14 and VvMYB15, and of genes encoding for chalcone synthases.ResultsDowny mildew incidence and severity ranged from nihil to high in the grapevine genotypes considered, being low to moderate in a subgroup of V. vinifera genotypes. The constitutive expression of the stilbene synthase genes as well as the extent of their transcriptional activation following P. viticola inoculation appeared to be inversely related to the proneness to develop disease symptoms upon infection. In a specular manner, following P. viticola inoculation all the chalcone synthase genes were up-regulated in the susceptible grapevine genotypes and down-regulated in the resistant ones. The infection brought by P. viticola appeared to elicit a co-ordinated and sequential transcriptional activation of distinct stilbene synthase genes subsets, each of which may be regulated by a distinct and specific MYB transcription factor.ConclusionsThe present results suggest that the induction of stilbene biosynthesis may contribute to the basal immunity against the downy mildew of grapevine, thus representing an adaptive resistance trait to recover, in both cultivated and wild V. vinifera germplasm. During the early stages of P. viticola infection, an antagonistic interaction between flavonol and stilbene biosynthesis might occur, whose outcome might determine the subsequent extent of disease symptoms. Further studies are needed to decipher the possible regulatory mechanisms involved in the antagonistic crosstalk between these two metabolic pathways in resistant and susceptible genotypes in response to P. viticola.

Droplet-vitrification cryopreservation of in vitro-grown shoot tips of grapevine (Vitis spp.)

An efficient and broad-spectrum protocol for cryopreservation of Vitis spp. shoot tips by droplet-vitrification is reported. Shoot tips (1.0 mm) containing 5–6 leaf primordia (LPs) were precultured for 3 d with a preculture medium containing 0.3 M sucrose, 0.16 μM glutathione, and 0.14 μM ascorbic acid. Precultured shoot tips were treated for 20 min at 24°C with a loading solution composed of 2 M glycerol and 0.4 M sucrose, followed by exposure at 0°C to half-strength plant vitrification solution 2 (PVS2) for 30 min, and then full-strength PVS2 for 50 min. Dehydrated shoot tips were transferred into 2.5-μL PVS2 carried on aluminum foil, prior to a direct immersion in liquid nitrogen. With this method, an average shoot regrowth level of 50.5% was obtained from cryopreserved shoot tips in six V. vinifera genotypes (three wine cultivars, two table cultivars, and one rootstock) and two V. pseudoreticulata genotypes. Vegetative growth of the regenerants recovered from cryopreservation, significantly increased as the number of subculture cycles increased and was greater than the control after the third subculture following cryopreservation. Inter-simple sequence repeats (ISSR) and random amplification of polymorphic DNA (RAPD) analyses did not detect any polymorphic loci in the plants of V. vinifera L. cv. ‘Cabernet Sauvignon’ from cryopreserved shoot tips compared to the original cultures. This droplet-vitrification cryopreservation method provides a technical platform to set up cryobanks of Vitis spp.

The metabolomic profile of red non-V. vinifera genotypes

Wild American genotypes represent an important part of the Vitis germplasm in relation to grape improvement. Today, these genotypes are currently involved in breeding programmes in order to introgress traits resistant to pests and diseases in V. vinifera cultivars. Nevertheless, the metabolic composition of their grapes has not been widely investigated. This study aimed to explore in detail the metabolomic profile in terms of simple phenolic, proanthocyanidin, anthocyanin and lipid compounds in two hybrids and five American genotypes. The results were compared with those of two V. vinifera cultivars. A multi-targeted metabolomics approach using a combination of LC-MS and LC-DAD methods was used to identify and quantify 124 selected metabolites. The genotypes studied showed considerable variability in the metabolomic profile according to the grape composition of V. vinifera and other Vitis genotypes. As regards the composition of anthocyanins, not all wild genotypes contained both mono- and di-glucoside derivatives. Wild genotype 41B and V. vinifera cultivars contained only monoglucoside anthocyanins. The proanthocyanidins of non-V. vinifera genotypes were mainly rich in oligomers and short-chain polymers. The analysis of lipids in wild Vitis genotypes, here reported for the first time, showed the existence of a certain diversity in their composition suggesting a strong influence of the environmental conditions on the general lipid pattern.

Adaptive strategies of two Mediterranean grapevines varieties (Aragonez syn. Tempranillo and Trincadeira) face drought: physiological and structural responses

At Mediterranean regions and particularly in southern Portugal, it is imperative to identify grape varieties more adapted to warm and dry climates in order to overcome future climatic changes. Two Vitis vinifera genotypes, Aragonez (syn. Tempranillo) and Trincadeira, were selected to assess their physiological responses to soil water stress. Vines were subjected to four irrigation regimes: irrigated during all phenological cycle, non-irrigated during all phenological cycle, non irrigated until veraison, irrigated after veraison. Predawn leaf water potential was much higher in Trincadeira than Aragonez in non-irrigated plants. This result is in accordance with its higher stomatal control efficiency in this variety (Trincadeira). Photosynthetic capacity (Amax at saturating light intensity) decreased due to stomatal and biochemical limitations under water stress. However, recovery capacity of leaf water status after irrigation was faster in Trincadeira. Yield and yield x Brix increased when irrigation occurred after veraison, particularly in Trincadeira. These results show that Trincadeira presents a drought adaptation than Aragonez. Ratio of variable to maximum fluorescence Fv/Fm and total leaf chlorophyll related with leaf water potential for both species. Reflectance Normalized Difference Vegetation Index (NDVI705), Red Edge Inflexion Point Index and Photochemical Reflectance Index were related with irrigation treatment. Relative water content and specific leaf area were similar between varieties. In conclusion, we suggested that there is variation among the genotypes and the main physiological parameters for variety selection, for drought, were leaf water potential, stomatal conductance and reflectance indexes.

ABA-mediated responses to water deficit separate grapevine genotypes by their genetic background.

BackgroundABA-mediated processes are involved in plant responses to water deficit, especially the control of stomatal opening. However in grapevine it is not known if these processes participate in the phenotypic variation in drought adaptation existing between genotypes. To elucidate this question, the response to short-term water-deficit was analysed in roots and shoots of nine Vitis genotypes differing in their drought adaptation in the field. The transcript abundance of 12 genes involved in ABA biosynthesis, catabolism, and signalling were monitored, together with physiological and metabolic parameters related to ABA and its role in controlling plant transpiration.ResultsAlthough transpiration and ABA responses were well-conserved among the genotypes, multifactorial analyses separated Vitis vinifera varieties and V. berlandieri x V. rupestris hybrids (all considered drought tolerant) from the other genotypes studied. Generally, V. vinifera varieties, followed by V. berlandieri x V. rupestris hybrids, displayed more pronounced responses to water-deficit in comparison to the other genotypes. However, changes in transcript abundance in roots were more pronounced for Vitis hybrids than V. vinifera genotypes. Changes in the expression of the cornerstone ABA biosynthetic gene VviNCED1, and the ABA transcriptional regulator VviABF1, were associated with the response of V. vinifera genotypes, while changes in VviNCED2 abundance were associated with the response of other Vitis genotypes. In contrast, the ABA RCAR receptors were not identified as key components of the genotypic variability of water-deficit responses. Interestingly, the expression of VviSnRK2.6 (an AtOST1 ortholog) was constitutively lower in roots and leaves of V. vinifera genotypes and higher in roots of V. berlandieri x V. rupestris hybrids.ConclusionsThis study highlights that Vitis genotypes exhibiting different levels of drought adaptation differ in key steps involved in ABA metabolism and signalling; both under well-watered conditions and in response to water-deficit. In addition, it supports that adaptation may be related to various mechanisms related or not to ABA responses.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0778-4) contains supplementary material, which is available to authorized users.

GEOGRAPHIC TREND OF BUD HARDINESS RESPONSE IN VITIS RIPARIA

A major goal of grapevine breeding efforts for production outside of Mediterranean climates is the production of cultivars that have cold tolerance phenotypes. Typically, grapevine breeders use midwinter bud hardiness measures as the descriptive phenotype for cold tolerance. Historical practices of bud cutting and more modern day differential thermal analysis of low temperature exotherms allows for an accurate, quantitative measure of bud hardiness. In our recent studies we have examined the relationship between cold hardiness and dormancy requirements, and our results preliminarily suggest a geographic pattern associated with dormant tissue temperature response and midwinter hardiness in Vitis riparia. The data presented here represent two years of hardiness measures for different Vitis riparia and Vitis vinifera genotypes.

First clues on a jasmonic acid role in grapevine resistance against the biotrophic fungus Plasmopara viticola

Plants are sessile organisms being constantly under a wide array of environmental pressures. Their resistance against biotic stress is regulated by phytohormones, of which jasmonic acid (JA) plays an important role against necrotrophic pathogens and herbivorous insects whereas salicylic acid (SA) plays a crucial role in plant defence against biotrophic and hemi-biotrophic pathogens, as well as in the establishment of systemic acquired resistance. Plasmopara viticola is a biotrophic oomycete responsible for one of the most important diseases in viticulture. Recent studies have shown that JA-signalling may be playing an important role on grapevine resistance against this biotrophic pathogen. Expression of enzymes associated to JA biosynthesis (LOX2, AOS, AOC, OPR3), activation (JAR1) and signalling (COI1) was analysed in two Vitis vinifera genotypes with different degrees of resistance towards P. viticola. Our results provide the first clues for a JA-signalling role in grapevine defence against this fungal biotroph.

Evaluation of Yield and Healthiness of Twenty Table Grapevine Cultivars Grown in Central Poland

Abstract During the years 2008-2013, 20 table grape cultivars grown in Skierniewice (Central Poland) were assessed. Among the assessed cultivars, two - ‘Chasselas Blanc’ (standard) and ‘Favorit’ belonged to V. vinifera. Eighteen interspecific hybrids - ‘Aron’, ‘Esther’ (‘Eszter’), ‘Fanny’, ‘Flora’, ‘Galanth’, ‘Ganita’, ‘Garant’, ‘Katharina’, ‘Lidi’, ‘Lilla’, ‘Muscat Bleu’, ‘Nelly’, ‘Osella’, ‘Philipp’, ‘Rosetta’, ‘Rosina’, ‘Timur’ and ‘Verdelet’ were bred in various European countries. Vines, grafted on ‘Kober 5 BB’ rootstock, were planted in 2007 and annually covered for winter. Taking into account productivity, quality of fruits, susceptibility to frost damage and fungal diseases, the Swiss ‘Muscat Bleu’ and German ‘Garant’ proved most suitable for cultivation in the conditions of Central Poland. Plants of all cultivars belonging to the group of interspecific hybrids were less susceptible to infections caused by fungal pathogens than plants of V. vinifera genotypes. The assessment of frost resistance based on the observation of those parts of bushes, which were not covered, showed high diversification among the interspecific hybrids.

A small XY chromosomal region explains sex determination in wild dioecious V. vinifera and the reversal to hermaphroditism in domesticated grapevines.

BackgroundIn Vitis vinifera L., domestication induced a dramatic change in flower morphology: the wild sylvestris subspecies is dioecious while hermaphroditism is largely predominant in the domesticated subsp. V. v. vinifera. The characterisation of polymorphisms in genes underlying the sex-determining chromosomal region may help clarify the history of domestication in grapevine and the evolution of sex chromosomes in plants. In the genus Vitis, sex determination is putatively controlled by one major locus with three alleles, male M, hermaphrodite H and female F, with an allelic dominance M > H > F. Previous genetic studies located the sex locus on chromosome 2. We used DNA polymorphisms of geographically diverse V. vinifera genotypes to confirm the position of this locus, to characterise the genetic diversity and traces of selection in candidate genes, and to explore the origin of hermaphroditism.ResultsIn V. v. sylvestris, a sex-determining region of 154.8 kb, also present in other Vitis species, spans less than 1% of chromosome 2. It displays haplotype diversity, linkage disequilibrium and differentiation that typically correspond to a small XY sex-determining region with XY males and XX females. In male alleles, traces of purifying selection were found for a trehalose phosphatase, an exostosin and a WRKY transcription factor, with strikingly low polymorphism levels between distant geographic regions. Both diversity and network analysis revealed that H alleles are more closely related to M than to F alleles.ConclusionsHermaphrodite alleles appear to derive from male alleles of wild grapevines, with successive recombination events allowing import of diversity from the X into the Y chromosomal region and slowing down the expansion of the region into a full heteromorphic chromosome. Our data are consistent with multiple domestication events and show traces of introgression from other Asian Vitis species into the cultivated grapevine gene pool.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0229-z) contains supplementary material, which is available to authorized users.

Reference Gene Selection and Validation for the Early Responses to Downy Mildew Infection in Susceptible and Resistant Vitis vinifera Cultivars

The pivotal role of cultivated grapevine (Vitis vinifera L.) in many countries economy is compromised by its high susceptibility to Plasmopara viticola, the causal agent of downy mildew disease. Recent research has identified a set of genes related to resistance which may be used to track downy mildew infection. Quantification of the expression of these resistance genes requires normalizing qPCR data using reference genes with stable expression in the system studied. In this study, a set of eleven genes (VATP16, 60 S, UQCC, SMD3, EF1α, UBQ, SAND, GAPDH, ACT, PsaB, PTB2) was evaluated to identify reference genes during the first hours of interaction (6, 12, 18 and 24 hpi) between two V. vinifera genotypes and P. viticola. Two analyses were used for the selection of reference genes: direct comparison of susceptible, Trincadeira, and resistant, Regent, V. vinifera cultivars at 0 h, 6, 12, 18 and 24 hours post inoculation with P. viticola (genotype effect); and comparison of each genotype with mock inoculated samples during inoculation time-course (biotic stress effect). Three statistical methods were used, GeNorm, NormFinder, and BestKeeper, allowing to identify UBQ, EF1α and GAPDH as the most stable genes for the genotype effect. For the biotic stress effect, EF1α, SAND and SMD3 were the most constant for the susceptible cultivar Trincadeira and EF1α, GAPDH, UBQ for the resistant cultivar Regent. In addition, the expression of three defense-related transcripts, encoding for subtilisin-like protein, CYP and PR10, was analysed, for both datasets, during inoculation time-course. Taken together, our results provide guidelines for reference gene(s) selection towards a more accurate and widespread use of qPCR to study the first hours of interaction between different grapevine cultivars and P. viticola.

Quantification of Stilbenes in Vitis Genotypes with Different Levels of Resistance to Plasmopara viticola Infection

Stilbenic phytoalexins have been associated with disease resistance. In Vitis spp., stilbene synthesis can be induced by UV irradiation, treatment with a variety of substance extracts, and inoculation with Botrytis cinerea or Plasmopara viticola . The aim of the present work was to examine the relationship between stilbene production and the level of resistance of different Vitis genotypes to P. viticola . The ability of different grapevine genotypes ( Vitis vinifera L. cvs. Tempranillo, Touriga Nacional, Pinot noir, and Cabernet Sauvignon and Vitis riparia cv. Gloire de Montpellier) to resist Plasmopara viticola infection was assessed via their potential to accumulate toxic stilbenic phytoalexins. Leaf discs taken from plants belonging to these genotypes were inoculated with P. viticola sporangia and disease severity was determined five days later. Stilbene production was quantified in similar leaf material at 6, 24, 48, and 72 hr postinoculation. After P. viticola infection, the resistant genotype V. riparia showed high production of the phytotoxic stilbenes ɛ- and δ-viniferin, which limited the development of the pathogen and prevented it from producing spores. Indeed, this genotype was associated with the lowest sporulation values. No relationship was observed, however, between resistance and these compounds in the V. vinifera genotypes. Further study is required to define the role of stilbenic phytoalexins in resistance to P. viticola.

Profiling of Hydroxycinnamoyl Tartrates and Acylated Anthocyanins in the Skin of 34 Vitis vinifera Genotypes

The diversity of berry skin flavonoids in grape genotypes has been previously widely investigated with regard to major compounds (nonacylated anthocyanins and flavonols), but much less with regard to acylated anthocyanins and hydroxycinnamoyl tartrates (HCTs). In this study, the composition of the phenolic fraction of the berry skin (free and acylated anthocyanins, flavonols, and HCTs) was assessed on 34 grapevine genotypes grown in a collection vineyard in northwestern Italy. The phenolic fraction was profiled on berries collected in the same vineyard, at the same ripening level across two successive vintages. The anthocyanin, HCT, and flavonol profiles were specific of each genotype, and the first two were relatively little affected by the vintage. A wide diversity in the polyphenolic fraction was shown among cultivars. Besides expected discriminatory effects of free anthocyanins and flavonol profiles, principal component analyses allowed a good discrimination of cultivars on the basis of coumaroylated anthocyanins and of the HCT profile. Anthocyanins were mostly acylated by aromatic acids, and acylation was independent from the anthocyanin substrate. HCTs were present mostly as coumaroyl and caffeoyl derivatives, and no correlation was observed between the same acylation patterns of tartrate and of anthocyanins. The results of this study are discussed in the light of new hypotheses on still unknown biosynthetic steps of phenolic substances and of the potential use of these substances in discrimination and identification of different grape cultivars in wines.

Cultivar-specific kinetics of gene induction during downy mildew early infection in grapevine

The oomycete pathogen Plasmopara viticola (Berk. et Curt.) Berl. et de Toni is the causing agent of the destructive downy mildew disease in grapevine. Despite the advances towards elucidation of grapevine resistance mechanisms to downy mildew, increased knowledge of the biological and genetic components of the pathosystem is important to design suitable breeding strategies. Previously, a cDNA microarray approach was used to compare two Vitis vinifera genotypes Regent and Trincadeira (resistant and susceptible to downy mildew, respectively) in field conditions. The same cDNA microarray chip was used to confirm field-based results and to compare both genotypes under greenhouse conditions at 0, 6, and 12h post-inoculation with P. viticola. Results show that when comparing both cultivars after pathogen inoculation, there is a preferential modulation of several defense, signaling, and metabolism associated transcripts in Regent. Early transcriptional changes are discussed in terms of genetic background and resistance mechanism. This study is the first to directly compare resistant and susceptible cultivars responses as early as 6hpi with P. viticola, providing several candidate genes potentially related to the expression of resistance traits.

A Strategy to Investigate the Intravarietal Genetic Variability in Vitis vinifera L. for Clones and Biotypes Identification and to Correlate Molecular Profiles with Morphological Traits or Geographic Origins

Grapevine is the most economically important and widely cultivated fruit crop in the world. Molecular markers have been used on Vitis vinifera to distinguish among both varieties and clones. Microsatellites are used to fingerprint varieties and several other techniques, reported in many papers, are used to analyze the differences among clones, but it is not available in the literature as a well defined strategy to screen a large number of Vitis cultivars. In fact, it is often necessary to use different techniques to investigate the genetic variability in different grapevine varieties and a proposed technique is used to study a cultivar, which is often not suitable for either the study of another cultivar or compare the genetic relationship among various cultivars. We describe here a strategy used for the analysis of several grapevine cultivars to describe a universal method to obtain DNA polymorphisms of Vitis vinifera genotypes from the same cultivar by using amplified fragment length polymorphism (AFLP), selective amplification of microsatellite polymorphic loci (SAMPL), microsatellites AFLP (M-AFLP), and ISSR molecular markers. The strategy here adopted permitted both to identify different biotypes (i.e., Primitivo), accessions (i.e., Garnacha tinta), and clones (i.e., Callet, Manto Negro, Moll) among the variability of same variety and to correlate the genetic differences to their geographical origins (i.e., Garnacha tinta; Malvasia nera di Brindisi/Lecce) or morphological traits (i.e., Malvasia of Candia). Here is also described the application of the protocol that allows to highlight the genetic variability accumulated during centuries of cultivations and selections of the same variety in different environments by vine growers.

Profiling of Resveratrol Oligomers, Important Stress Metabolites, Accumulating in the Leaves of Hybrid Vitis vinifera (Merzling × Teroldego) Genotypes Infected with Plasmopara viticola

In the Vitaceae, viniferins represent a relatively restricted group of trans-resveratrol oligomers with antifungal properties, thus enabling plants to cope with pathogen attack. The aim of this study was to perform isolation and structural characterization of the whole class of viniferins accumulating in the leaves of hybrid Vitis vinifera (Merzling × Teroldego) genotypes infected with Plasmopara viticola . Infected leaves of resistant plants were collected 6 days after infection, extracted with methanol, and prepurified by flash chromatography using ENV+ and Toyopearl HW 40S resins. Further fractionation using normal-phase preparative chromatography and then reversed-phase preparative chromatography allowed isolation of 14 peaks. The isolated compounds were identified using advanced mass spectrometry techniques and extensive one- and two-dimensional nuclear magnetic resonance measurements, UV, CD, optical properties, and molecular mechanic calculations. The results demonstrated the presence in infected leaves of seven dimers (six stilbenes and one stilbenoid), of which four were new in grapevine (ampelopsin D, quadrangularin A, E-ω-viniferin, and Z-ω-viniferin), four trimers (three stilbenes and one stilbenoid), of which two (Z-miyabenol C and E-cis-miyabenol C) were new in grapevine, three tetramer stilbenoids, all new in grapevine, isohopeaphenol, ampelopsin H, and a vaticanol C-like isomer. The isolation of a dimer deriving from the condensation of (+)-catechin with trans-caffeic acid also indicated that other preformed phenolics are structurally modified in tissues infected with P. viticola.

Vine performance and grape composition as affected by early-season source limitation induced with anti-transpirants in two red Vitis vinifera L. cultivars

Background and Aims: Previous work has shown that an early (i.e. pre-flowering) source limitation achieved with either hand or mechanical basal shoot zone defoliation is effective in controlling yield while improving grape composition in several environments and Vitis vinifera genotypes. Our study was designed to determine whether similar results can be reproduced by using a film-forming anti-transpirant. Methods and Results: The entire canopies of field grown cvs. Sangiovese and Ciliegiolo vines were treated twice pre-flowering with the anti-transpirant Vapor Gard® (Intrachem Bio Italia, Grassobbio, BG, Italy) (T) and compared with an unsprayed control (C). Leaf assimilation and transpiration in both cultivars showed similar reductions (30–70%) for several weeks after spraying as compared with control vines, while intrinsic water use efficiency increased in treated vines soon after first application and after veraison. In Sangiovese, treated vines showed reduced yield, berry weight, bunch compactness and, on a 2-year basis, lower vigour and unchanged vine capacity every year. At harvest, treated vines showed higher °Brix in all seasons and higher anthocyanin concentration in 2 out of 3 years. Results of a 2-year run in Ciliegiolo mimicked those of Sangiovese in terms of yield regulation. Conclusions: Early season applications of a film-forming anti-transpirant caused a leaf function limitation strong enough to reduce yield and bunch compactness through smaller final berry size. Significance of the Study: Anti-transpirant applications can be proposed as a much easier way than manual or mechanical leaf removal to induce crop regulation through early source limitation.