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The effects of the spatial and temporal variability of environmental factors on viticulture are particularly important in mountainous wine regions due to their complex geomorphology. A typical example is Valtellina, an Italian valley in the middle of the Alpine chain known for its wine production. The aim of this work was to assess the effects of the current climatic conditions on Alpine viticultural production by evaluating the relationship between sugar accumulation, acid degradation, and environmental factors. To achieve this objective, a 21-year time series of ripening curves from 15 vineyards (cv Nebbiolo) along the Valtellina wine-growing belt was collected. The ripening curves were then analysed in conjunction with meteorological data to assess the influence of geographical and climatic characteristics, as well as other limiting environmental factors, on grape ripening. Valtellina is currently characterised by a stable warm phase, with yearly precipitation slightly higher than in the past. In this context, the timing of ripening and the level of total acidity are correlated with altitude, temperature, and summer thermal excess. Precipitation shows good correlations with all the maturity indices, so higher precipitation leads to late ripening and higher total acidity. Considering the oenological goal of local wineries, the results suggest that the Alpine area of Valtellina is currently facing favourable environmental conditions, with early development and increased levels of sugar while maintaining good levels of acidity.

BACKGROUND: The pathway of anthocyanin biosynthesis, and its alterations leading to berry colour modification, are well known in grape skin. This variability could affect both quantity and quality of pigment accumulation. OBJECTIVE: The present work is focused on 15 grapevine cultivars selected to represent a high variability in the phenotypical colour traits in order to highlight new polymorphisms related to the flavonoid pathway. METHODS: Twenty-one genes involved in the biosynthetic pathway of anthocyanins were studied via targeted resequencing and were correlated with phenotypic data (anthocyanin profiles and spectroscopy indices). RESULTS: Single nucleotide polymorphism (SNP) and InDel (insertion/deletion) polymorphisms were detected. Out of 1751 polymorphic loci, 68% were SNPs and 32% were InDels (568). Cluster analysis and SPLS-DA were used to investigate the genetic relationships among the cultivars, confirming the large range of phenotypical variability. Statistically significant correlations were detected between accumulation of cyanidin-based anthocyanins and genetic polymorphisms in two structural genes and one transcription factor putatively involved in the anthocyanin biosynthetic pathway. CONCLUSIONS: The understanding of the polymorphisms related to the anthocyanin accumulation could support future selection of new pink table grape varieties with increased appeal on the consumers.

Weather data from the Prosecco area were used to apply a proposed model for estimating δ18O values in wine (HV; Hermann and Voerkelius 2008) and to determine the spatio-temporal variability of these values. Eleven reference stations provided meteorological data from 1973 to 2017. The model revealed interannual and spatial variability similar to that observed for other grape varieties or viticultural areas, and we highlight the need for more careful consideration of meteorological factors in causing variation in δ18O values. Meteorological modeling of isotopic values can help constrain sampling procedures aimed at collecting representative data from different Prosecco production areas and estimating δ18O ranges for each year in the “Prosecco” region. Estimated values revealed a significant degree of temporal variability across the 11 sites and, consequently, across years. δ18O values for 36 bottled “Prosecco” wines collected from 2012 to 2017 were compared with the range defined by the HV model for each corresponding year, with good data consistency.

The Eurasian grapevine (Vitis vinifera), a species cultivated worldwide for high-quality wine production, is extremely susceptible to the agent of downy mildew, Plasmopara viticola. Nevertheless, germplasm from Georgia (Southern Caucasus, the first grapevine domestication centre), characterized by a high genetic variability, showed resistance traits to P. viticola. The cultivar Mgaloblishvili exhibited the most promising phenotype in terms of resistance against P. viticola. Its defence response results in: i) low disease intensity; ii) low sporulation; iii) damaged mycelium; iv) production of antimicrobial compounds such as volatile organic compounds (VOCs), whose effectiveness on the pathogen was evaluated by leafdisc assays. At the transcriptomic level, its resistance mechanism is determined by the differential expression of both resistance and susceptible genes. The resistance genes are related to: i) pathogen recognition through PAMP, DAMP and effector receptors; ii) ethylene signalling pathway; iii) synthesis of antimicrobial compounds (VOCs) and fungal wall degrading enzymes; iv) development of structural barriers (cell wall reinforcement). The first putative susceptible gene was the transcription factor VviLBDIf7 gene, whose validation was carried out by dsRNA (double-stranded RNA) assay. In this work, these unique results on plant-pathogen interaction are reviewed with the aim of developing new strategies to control the disease.

Background and Aims: Nebbiolo grapes are used to produce Sfursat wine, following partial dehydration. This research aimed to clarify the influence of fruit exposure to light and postharvest water loss on the concentration of green leaf volatiles (GLVs) and lipoxygenase (LOX) and alcohol dehydrogenase (ADH) activity of grapes. Methods and Results: Nebbiolo grapes from Control vines (no defoliation) (ND) and from vines defoliated at fruitset (DFS) or defoliated post-veraison (DPV) were harvested at about 23°Brix and dehydrated at 10 and 20°C, 60% RH and air flow of 1.5 m/s. Berries were sampled at 10 and 20% mass loss (ML). Significant differences in crop yield, bunch mass and berry mass were observed. As expected, the higher the dehydration temperature, the faster the dehydration process: 20% ML at 20°C occurred between 18 and 25 days, the shortest time corresponding to ND and the longest to DFS; at 10°C, the dehydration lasted between 27 and 32 days. At 10°C, the ADH activity was almost double that at 20°C, and in DFS was much higher than in other samples. At harvest, LOX did not show any difference among the samples, while at 10°C and 10% ML, the enzyme activity increased significantly and then declined at 20% ML, especially in defoliated samples. At harvest, the total free GLVs associated with the metabolism of lipid oxidation were 9434, 7212 and 11 656 μg/kg dry weight (DW) in ND, DFS and DPV samples, respectively; the total bound GLVs lipid-derived were 7599, 18 486 and 15 409 μg/kg DW in ND, DFS and DPV samples, respectively. During dehydration at 10°C, the ML induced ADH + LOX activity, especially in defoliated samples, but the bound GLVs, produced by defoliation, greatly decreased. Conclusions: Defoliation affected the response of Nebbiolo grapes to dehydration temperature: postharvest cold stress (10°C) and ML induced glycosylation of GLVs, alcohol formation (via ADH) and membrane oxidation (via LOX); a further stress effect was observed with leaf removal, regardless of the time of application. Significance of the Study: The timing of defoliation and postharvest dehydration temperature are significant factors to mitigate the postharvest stress response of Nebbiolo grapes.

BACKGROUND AND AIMS: The growth and development of grapevine is constrained by temperature, affecting the bulk of physiological processes of the plant. The aim of this study was to evaluate the effects of climate change on thermal resources and limitations in the context of Georgia, one of the oldest viticultural areas in the world. METHODS AND RESULTS: The analysis on daily series of temperature for the time period 1974–2013 for the main viticultural areas of Georgia shows that an abrupt change to warmer temperature occurred in 1994, leading to a decline in low temperature stress and an increase in high temperature stress, associated with more frequent heat waves. The availability of thermal resources for grapevine growth remained unchanged. CONCLUSIONS: In Georgia, the shift to warmer temperature did not affect the availability of thermal resources for grapegrowing. Although some attention should be paid to possible damage due to an earlier budburst and increased frost risk. Furthermore, it is important to highlight the strong increase of summer heatwaves with potential negative impacts on grape composition and phenolic maturity, when combined with severe water stress. SIGNIFICANCE OF THE STUDY: Quantitative studies of the effects of climate change on Georgian viticulture are essential to develop adaptation strategies based on either germplasm (e.g. rootstocks and cultivars) and agronomical practices (e.g. pruning, trellis systems, soil and water management).

A large repository of 441 rootstocks and other non-vinifera grape cultivars was established, beginning in 2013, by the University of Milan with the aim of collecting most of the genetic variability of Vitis species useful for rootstock genetic improvement. This kind of collection is the largest in Italy, with accessions from different donor institutes in California, Spain and Italy, and also encompassing progenies obtained by University of Milan breeding programs. A preliminary genetic characterization was performed, as is usually done for better management of grape germplasm. Eighty-six per cent of the accessions were evaluated by genotyping with simple sequence repeat (SSR) markers and also by phenotyping the sex of flowers. Twenty-two carefully selected and highly polymorphic SSR markers were used, out of 41 taken into consideration, which encompassed the nine markers applied internationally for V. vinifera genotyping and 26 VChr SSRs having a longer core tandem repeat. However, five of the 22 markers were shown to be critical when applied on a large scale for genotyping of non-vinifera plants and were subsequently discarded. SSR profile comparisons showed that more than a third of the accessions were redundant. Fewer than half were identified as true-to-type, and more than a third remained anonymous. These anonymous, as-yet uncharacterized genotypes represent a precious reservoir of genetic diversity. Analysis of the genetic structure revealed four main groups, with more than a third of genotypes classified as admixed. A genetic core collection able to capture the whole allelic variation was set up as a valuable starting point for both rootstock breeding and genome-wide association studies.

Microsatellite markers are a valuable tool to facilitate the management of germplasm collections and assess genetic diversity. This study reports the genetic characterization of a large collection of 379 rootstocks and other non-vinifera accessions maintained at the University of Milan, Italy. Accessions were genotyped with 22 highly polymorphic microsatellite markers, including the nine “international” loci used for grapevine identification, three VMC, three VrZAG, and seven VChr loci; 17 loci were retained to identify cultivars, investigate genetic diversity, analyze pedigrees, infer population structure, and design a core collection. This study identified 232 unique genotypes; the allelic profiles of 70 rootstocks were confirmed according to the literature and databases, while the profiles of 43 rootstocks were proposed for the first time. Pedigree analysis highlighted 77 parents-offspring trios and 44 parent-offspring relationships, some of them already known and others new. Genetic-structure analysis showed a more likely number of three ancestral groups, with a high percentage of admixed samples. A structure based on the genetic background of genotypes was not observed. A core collection of 70 genotypes captured 100% of the entire number (373) of detected alleles. Most of these genotypes were unidentified or poorly characterized. The information provided in this paper could assist breeders in their efforts to exploit still unexplored individuals useful for long-term breeding plans.

Downy mildew, caused by the oomycete Plasmopara viticola, is one of the diseases causing the most severe economic losses to grapevine (Vitis vinifera) production. To date, the application of fungicides is the most efficient method to control the pathogen and the implementation of novel and sustainable disease control methods is a major challenge. RNA interference (RNAi) represents a novel biotechnological tool with a great potential for controlling fungal pathogens. Recently, a candidate susceptibility gene (VviLBDIf7) to downy mildew has been identified in V. vinifera. In this work, the efficacy of RNAi triggered by exogenous double-stranded RNA (dsRNA) in controlling P. viticola infections has been assessed in a highly susceptible grapevine cultivar (Pinot noir) by knocking down VviLBDIf7 gene. The effects of dsRNA treatment on this target gene were assessed by evaluating gene expression, disease severity, and development of vegetative and reproductive structures of P. viticola in the leaf tissues. Furthermore, the effects of dsRNA treatment on off-target (EF1α, GAPDH, PEPC, and PEPCK) and jasmonic acid metabolism (COI1) genes have been evaluated. Exogenous application of dsRNA led to significant reductions both in VviLBDIf7 gene expression, 5 days after the treatment, and in the disease severity when artificial inoculation was carried out 7 days after dsRNA treatments. The pathogen showed clear alterations to both vegetative (hyphae and haustoria) and reproductive structures (sporangiophores) that resulted in stunted growth and reduced sporulation. Treatment with dsRNA showed signatures of systemic activity and no deleterious off-target effects. These results demonstrated the potential of RNAi for silencing susceptibility factors in grapevine as a sustainable strategy for pathogen control, underlying the possibility to adopt this promising biotechnological tool in disease management strategies.

Background Understanding the complexity of the vine plant’s response to water deficit represents a major challenge for sustainable winegrowing. Regulation of water use requires a coordinated action between scions and rootstocks on which cultivars are generally grafted to cope with phylloxera infestations. In this regard, a genome-wide association study (GWAS) approach was applied on an ‘ad hoc’ association mapping panel including different Vitis species, in order to dissect the genetic basis of transpiration-related traits and to identify genomic regions of grape rootstocks associated with drought tolerance mechanisms. The panel was genotyped with the GrapeReSeq Illumina 20 K SNP array and SSR markers, and infrared thermography was applied to estimate stomatal conductance values during progressive water deficit. Results In the association panel the level of genetic diversity was substantially lower for SNPs loci (0.32) than for SSR (0.87). GWAS detected 24 significant marker-trait associations along the various stages of drought-stress experiment and 13 candidate genes with a feasible role in drought response were identified. Gene expression analysis proved that three of these genes (VIT_13s0019g03040, VIT_17s0000g08960, VIT_18s0001g15390) were actually induced by drought stress. Genetic variation of VIT_17s0000g08960 coding for a raffinose synthase was further investigated by resequencing the gene of 85 individuals since a SNP located in the region (chr17_10,497,222_C_T) was significantly associated with stomatal conductance. Conclusions Our results represent a step forward towards the dissection of genetic basis that modulate the response to water deprivation in grape rootstocks. The knowledge derived from this study may be useful to exploit genotypic and phenotypic diversity in practical applications and to assist further investigations.

The discovery of new mechanisms of resistance and natural bioactive molecules could be two of the possible ways to reduce fungicide use in vineyard and assure an acceptable and sustainable protection against Plasmopara viticola, the grapevine downy mildew agent. Emission of volatile organic compounds (VOCs), such as terpenes, norisoprenoids, alcohols and aldehydes, is frequently induced in plants in response to attack by pathogens, such as P. viticola, that is known to cause a VOCs increment in cultivars harboring American resistance traits. In this study, the role of leaf VOCs in the resistance mechanism of two resistant cultivars (Mgaloblishvili, a pure Vitis vinifera cultivar, and Bianca, an interspecific hybrid) and the direct antimicrobial activity of four selected VOCs have been investigated. The leaf VOCs profiles, analyzed through solid-phase microextraction gas chromatography-mass spectrometry analysis, as well as the expression of six terpene synthases (TPSs), were determined upon pathogen inoculation. In both cultivars, the expression pattern of six TPSs increased soon after pathogen inoculation and an increment of nine VOCs has been detected. While in Mgaloblishvili VOCs were synthesized early after P. viticola inoculation, they constituted a late response to pathogen in Bianca. All the four terpenes (farnesene, nerolidol, ocimene and valencene), chosen according to the VOC profiles and gene expression analysis, caused a significant reduction (53-100%) in P. viticola sporulation. These results support the role of VOCs into defense mechanisms of both cultivars and suggest their potential role as a natural and eco-friendly solution to protect grapevine from P. viticola.

Keywords: NaCl, Vitis, LC-ESI-MS/MS, carbon and energy metabolism, oxidative stress

Oxidations in grape berries are gaining major interest as they affect grape characteristics and quality. Considering berries, Reactive Oxygen Species are involved in the responses to both ripening process and stresses, including photooxidative sunburn. Redox metabolism involves a multitude of chemical and enzymatic reactions. In this study, four white grape cultivars were examined for natural ripening and photooxidative sunburn effects (obtained in artificial conditions) on berry pigmentation, chemical composition and enzymatic activity. The measured parameters included reflectance spectra, pigmentation (including berry browning), content of photosynthetic pigments, organic acid profiles, antioxidant activity, concentrations of antioxidants (total phenolics, ascorbic acid and reduced glutathione), enzymatic activities (guaiacol peroxidases, ascorbate peroxidase and catalase). The effects of the treatment (natural ripening and artificial photooxidative sunburn) on each considered parameter are described in the paper. Photooxidative sunburn strongly affected the contents of antioxidants and chlorophylls, increased the browning index and modulated the enzymatic activities investigated. Samples clearly clustered depending on the oxidation status. Furthermore, the PCA highlighted the similarities and differences in the responses to oxidative stress during ripening and photooxidative sunburn. PCA produced five functions with eigenvalues higher than 1, representing 87.03% of the total variability. In particular, the scores of the function 1 discriminated the samples based on the oxidation status, while the function 2 separated the samples based on the sampling date, representing the physiological responses characteristic of ripening. Our work sheds light on this topic, and will allow a more conscious vineyard management, thus supporting the agricultural adaptation to climate changes.

Grapevine domestication took place in the Caucasus area known as the Cradle of Viticulture, within or near the geographical area known as the Vavilov Triangle. The phytogenetic resources of Vitis sylvestris C.C.Gmel. have been previously collected and characterized, but the study on micro vinifications of wild grapevines from the Caucasus is new. In the present document, seven grape samples from female individuals of wild grapevine growing in the South Caucasus region were investigated to assess their oenological profile. Wine samples were obtained from the grapes collected from various populations of Armenia, Azerbaijan and Georgia in October 2013 and fermented by the native yeasts. Parameters determined in the wines were, among others, the concentration of ethanol (3.63 % - 10.15 %), pH (3.30 - 4.20), total acidity (1.2 - 10.7 g/L of tartaric acid), total polyphenol index (1.81 - 89.8) and colour intensity (2.59 - 20.76). This wide range of values is due to the different environmental conditions, the level of ripeness of harvested grapes and their genetic diversity. These data were compared with those obtained in micro vinifications of wild grapevines in Western Europe and wines of several international cultivars. The results of our research demonstrated, that the must of wild grape could be used to improve traditional wines giving them more colouration. This work was carried out under the project COST FA1003 Action “East–West Collaboration for Grapevine Diversity and Exploration and Mobilization of Adaptive Traits for Breeding” (2014-2018).

A prospecting of habitats and mechanical support host species for the climber Eurasian wild grapevine, Vitis vinifera L. subsp. sylvestris (Gmelin) Hegi, was carried out on 13 natural populations situated along river bank forests, floodplains and colluvial positions in Georgia (Marneuli, Mtskheta and Gori districts, Gardabani Protected area and Lagodekhi Reserve), Armenia (Akhtala and Tavoush regions) and Azerbaijan (Quba region) during survey of 2013. The research demonstrated that Eurasian wild grapevine (Vitis vinifera subsp. sylvestris) is found in Southern Caucasus in a wide variety of habitats always linked to water availability. Punica granatum trees are the commonest mechanical support for wild grapevine in the South Caucasus and Hedera helix often shares the same support trees. However we documented wild grapevines climbing on other 24 different species of trees and large shrubs and, further, 32 associated species. We determined, four different clusters of localities using Structure software and the Weighted Neighbor Joining tree. These clusters are characterized by specific mechanical support and accompanying species. Other vines competing for host with Eurasian wild grapevine belong to the genera Clematis, Hedera, Humulus, Smilax and Vitis ssp. Keywords: Armenia, Azerbaijan, Georgia, Lianas, Vines, Wild grapevines

Grape phylloxera (Daktulosphaira vitifoliae Fitch) induces root galls on tips of susceptible and partially resistant rootstocks. The monophagous parasite affects the host by inhibition of water- and mineral uptake, sink-source translocation, changes in secondary metabolisms and manipulation of root growth. Grafted phylloxerated vines rarely show severe plant damage. Compensation effects on leaf galled vines have been proposed, however no information is available for root galled vines. In two experiments we aimed to determine effects of root phylloxeration on the primary metabolism of Vitis spp. We hypothesise that affected vines respond with a compensation strategy consisting of an increased root growth, leaf respiration and photosynthetic activity. Experiment 1 was conducted to analyse phylloxeration effects on carbohydrate mobility within grafted vines (V. vinifera L. 'Pinot Noir' on SO4). Experiment 2 analyzed potential phylloxeration effects on vines under nitrogen deficiency on Teleki 5C (V. berlandieri × V. riparia). Assessed parameters included plant phenology, quantitative plant growth, levels of macro and micro nutrients, photosynthetic activity, gas exchange and activity of enzymes related to carbohydrate mobility (sucrose synthase, vacuolar invertase, cell wall invertase). Our results showed an increased root mass in combination with elevated carbon and nitrogen levels in the root system of phylloxerated vines. Gas exchange and enzymatic activity of enzymes related to carbohydrate mobility were increased upon phylloxeration. However shoot and berry growths were not reduced. In conclusion these results show that more carbohydrates are imported in the root system upon phylloxeration without reductions of shoot and berry growth indicating a compensation strategy of the host. However it is unclear whether grape phylloxera actively triggers the import of carbohydrates to the root system by potential effectors or the host counteracts the lack of nutrients withdrawn by the parasite.

A survey carried out in Georgian vineyards, located in the Khaketi region, in September 2013, showed the presence of vines of the cultivar Chardonnay with typical grapevine yellows (GY) symptoms including leaf discoloration and curling, berry shriveling, and irregular maturation of wood. In the same vineyards, bindweed (Convolvulus arvensis L.) plants showing shoot proliferation and leaf yellowing were found, suggesting the involvement of phytoplasmas in the disease etiology. Total DNA was extracted by a CTAB method from leaf veins of 18 symptomatic and two asymptomatic grapevines, and from four symptomatic and two asymptomatic bindweeds, and analyzed by PCR assays. Moreover, DNA extracted from ‘Candidatus Phytoplasma asteris’ strain SAY (group 16SrI), ‘Ca. P. solani’ strain STOL (group 16SrXII), and ‘Ca. P. ulmi’ strain EY1 (group 16SrV) were used as positive controls. DNA extracted from healthy periwinkle and a reaction mixture without template were employed as negative controls. Nested PCRs targeting the 16S rDNA, carried out using the primer pairs P1/P7 followed by R16F2n/R16R2 (1), produced a band of the expected size (1,250 nt) in all the symptomatic grapevine and bindweed plants, and in the positive controls. No amplification was observed with DNA from asymptomatic plants nor the negative controls. PCR products were sequenced by a commercial sequencing service (Primm, Milan, Italy). The 16S rDNA nucleotide sequences of phytoplasmas identified in all grapevines and in two bindweed samples shared >99.5% sequence identity with ‘Ca. P. solani’ reference strain STOL (GenBank Accession No. AF248959), and carried identical STOL-unique signature sequence and distinguishing sequence blocks (3). Moreover, nucleotide sequences of phytoplasmas identified in the other two bindweed samples shared >99.6% sequence identity with ‘Ca. P. convolvuli’ reference strain BY-S57/11 (JN833705) (2). RFLP and phylogenetic analyses confirmed the affiliation of the phytoplasma strains identified in grapevine and bindweed plants in Georgia to the species ‘Ca. P. solani’ (subgroup 16SrXII-A) and ‘Ca. P. convolvuli’ (subgroup 16SrXII-H). Representative 16S rDNA nucleotide sequences were deposited in NCBI GenBank website with accession nos. KF996535 and KF996536 (‘Ca. P. solani’ from grapevine and bindweed, respectively), and KF996537 (‘Ca. P. convolvuli’). Future studies will focus on investigating the spread and impact of ‘Ca. P. solani’-associated bois noir (BN) in Georgia. In particular, the identification of ‘Ca. P. solani’ in bindweeds suggested the presence of the insect Hyalesthes obsoletus, a polyphagous cixiidae responsible for BN phytoplasma transmission in vineyards in Europe. Accurate surveys and molecular analyses will be performed for identifying the insect vector(s) of the BN associated phytoplasma strains in Georgia. Additional studies will be performed to study the spread and impact of ‘Ca. P. convolvuli,’ identified only in Italy, Germany, Serbia, and Bosnia and Herzegovina (2), throughout the Caucasian countries. References: (1) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) M. Martini et al. Int. J. Syst. Evol. Microbiol. 62:2910, 2013. (3) F. Quaglino et al. Int. J. Syst. Evol. Microbiol. 63:2879, 2013.

Introgression of genetic resistance to fungal diseases from American and Asian Vitis species traditionally pursued in grape breeding programs, although facilitated by molecular tools, has an impact on wine quality that still slows down development of competitive varieties. A contribution to the genetic improvement of grapevines for resistance to pathogens may come from unexplored genetic resources of the Eurasian Vitis vinifera L. In the present study, a hundred grapevine accessions from Georgia, Armenia and Azerbaijan were genotyped with SSR markers linked to QTLs for resistance to downy and powdery mildew, and with 21 SSR markers widely used for genetic diversity and relationship analysis. Looking at population genetic structure, Armenian and Azerbaijani accessions fell within the same cluster and were included among the Central Asian grape varieties of a homogeneous dataset, while Georgian accessions formed a separate group. Pattern of SSR alleles flanking the locus Ren1 and associated with resistance to Erysiphe necator in 'Kishmish vatkana', 'Dzhandzhal kara' and other Central Asian cultivars were found in three varieties from the Azerbaijani population that reached very high scores when assessed for PM resistance.

Water availability is an important environmental factor in viticulture. In a climate change context, vineyard management should be adapted to the new conditions. Drought-resistant rootstocks need to be selected. In this paper, refectance spectroscopy is proposed as a new method to characterize the water stress efects on woody section pigmentations. Cabernet Sauvignon grafted on 4 diferent rootstocks (140Ru, 420A, M2 and M3) represented the plant material. Greenhouse controlled conditions allowed the comparison of well-watered (WW) and water-stressed (WS) plants. The physiological responses were characterized concerning daily water consumption, stem water potential, gas exchange, and plant growth. The water use eficiency was calculated and discussed as well. Spectroscopy analyses of woody sections indicated a major absorption band probably related to phenolic derivatives. Water stress produced characteristic spectrum modifications both in the Cabernet Sauvignon stem and in the rootstock xylem. These preliminary results encourage further studies addressed at the evaluation of drought-resistant genotypes, to distinguish their stress responses and to characterize the compositional aspects linked to drought tolerance.

Evidence from a preliminary survey highlighted that ‘Candidatus Phytoplasma solani’, the etiological agent of bois noir (BN) disease of grapevine, infects grapevine varieties in Georgia, a country of the South Caucasus. In this study, field surveys were carried out to investigate the BN symptom severity in international and Georgian native varieties. ‘Ca. P. solani’ was detected and identified by polymerase chain reaction-based amplification and restriction fragment length polymorphism analysis of 16S ribosomal DNA, and further characterized by multiple gene typing analysis (vmp1 and stamp genes). Obtained data highlighted that the majority of Georgian grapevine varieties showed moderate and mild symptoms, whereas international cultivars exhibited severe symptoms. Molecular characterization of ‘Ca. P. solani’ from grapevine revealed the presence of 11 distinct phytoplasma types. Only one type (VmGe12/StGe7) was identical to a strain previously reported in periwinkle from Lebanon; the other ‘Ca. P. solani’ types are described here for the first time. Phylogenetic analyses of vmp1 and stamp gene concatenated nucleotide sequences showed that ‘Ca. P. solani’ strains in Georgia are associated mainly with the bindweed-related BN host system. Moreover, the fact that ‘Ca. P. solani’ strains are distributed in grapevine cultivars showing a range of symptom intensity suggests a different susceptibility of such local cultivars to BN.

Wild Euro-Asiatic grapevine ( Vitis vinifera L. subsp. sylvestris (Gmelin) Hegi) is an opportunistic liana with reproductive patterns characterized both by vegetative propagation and sexual reproduction. Vegetative propagation would ensure a rapid vine regeneration and land colonization, while sexual reproduction would assure genetic recombination and chromosome re-assortment crucial for evolution and survival of the species. The aim of this study was the analysis of the parentage relationships within and between fourteen Italian wild grapevine populations, in order to characterize the natural mating system of this taxon. Beside parentage relationship analyses, the estimation of genetic diversity, genetic distance and genetic differentiation were assessed. The populations showed a good extent of genetic diversity and low levels of genetic distance and isolation between them, indicating gene flow among sites. This result was supported by parentage relationships between different populations. Nevertheless, populations from North Italy showed the lowest genetic diversity, while internal relatedness and inbreeding estimation values were higher than the populations from Central and Southern Italy. One of the northern populations resulted particularly high in inbreeding intensity. The parentage relationship analysis pointed out in all sites a, sometimes active, sexual reproduction within populations. Seed dispersal by frugivorous vectors among neighbouring sites seemed less frequent and depending on specific environmental circumstances.

Background The mountainous region between the Caucasus and China is considered to be the center of domestication for grapevine. Despite the importance of Central Asia in the history of grape growing, information about the extent and distribution of grape genetic variation in this region is limited in comparison to wild and cultivated grapevines from around the Mediterranean basin. The principal goal of this work was to survey the genetic diversity and relationships among wild and cultivated grape germplasm from the Caucasus, Central Asia, and the Mediterranean basin collectively to understand gene flow, possible domestication events and adaptive introgression. Results A total of 1378 wild and cultivated grapevines collected around the Mediterranean basin and from Central Asia were tested with a set of 20 nuclear SSR markers. Genetic data were analyzed (Cluster analysis, Principal Coordinate Analysis and STRUCTURE) to identify groups, and the results were validated by Nei’s genetic distance, pairwise FST analysis and assignment tests. All of these analyses identified three genetic groups: G1, wild accessions from Croatia, France, Italy and Spain; G2, wild accessions from Armenia, Azerbaijan and Georgia; and G3, cultivars from Spain, France, Italy, Georgia, Iran, Pakistan and Turkmenistan, which included a small group of wild accessions from Georgia and Croatia. Wild accessions from Georgia clustered with cultivated grape from the same area (proles pontica), but also with Western Europe (proles occidentalis), supporting Georgia as the ancient center of grapevine domestication. In addition, cluster analysis indicated that Western European wild grapes grouped with cultivated grapes from the same area, suggesting that the cultivated proles occidentalis contributed more to the early development of wine grapes than the wild vines from Eastern Europe. Conclusions The analysis of genetic relationships among the tested genotypes provided evidence of genetic relationships between wild and cultivated accessions in the Mediterranean basin and Central Asia. The genetic structure indicated a considerable amount of gene flow, which limited the differentiation between the two subspecies. The results also indicated that grapes with mixed ancestry occur in the regions where wild grapevines were domesticated. Electronic supplementary material The online version of this article (10.1186/s12870-018-1351-0) contains supplementary material, which is available to authorized users.

Background Roots play a central role in plant response to water stress (WS). They are involved in its perception and signalling to the leaf as well as in allowing the plant to adapt to maintaining an adequate water balance. Only a few studies have investigated the molecular/biochemical responses to WS in roots of perennial plants, such as grapevine. This study compares two grapevine rootstock genotypes (i.e. 101.14 and M4) with different tolerance to WS, evaluating the responses at proteomic and metabolite levels. Results WS induced changes in the abundance of several proteins in both genotypes (17 and 22% of the detected proteins in 101.14 and M4, respectively). The proteomic analysis revealed changes in many metabolic pathways that fitted well with the metabolite data. M4 showed metabolic responses which were potentially able to counteract the WS effects, such as the drop in cell turgor, increased oxidative stress and loss of cell structure integrity/functionality. However, in 101.14 it was evident that the roots were suffering more severely from these effects. We found that many proteins classified as active in energy metabolism, hormone metabolism, protein, secondary metabolism and stress functional classes showed particular differences between the two rootstocks. Conclusion The proteomic/metabolite comparative analysis carried out provides new information on the possible biochemical and molecular strategies adopted by grapevine roots to counteract WS. Although further work is needed to define in detail the role(s) of the proteins and metabolites that characterize WS response, this study, involving the M4 rootstock genotype, highlights that osmotic responses, modulations of C metabolism, mitochondrial functionality and some specific responses to stress occurring in the roots play a primary role in Vitis spp. tolerance to this type of abiotic stress. Electronic supplementary material The online version of this article (10.1186/s12870-018-1343-0) contains supplementary material, which is available to authorized users.

The objective of this work is to investigate the Holocenic climate cycles that may have influenced the domestication of grapevine in the Subcaucasian area and its subsequent spread in Eurasia. The analysis covered the longitudinal belt ranging from the Iberian Peninsula to Japan, seen as the preferential pathway for the Holocenic spread of grapevine and many other crops in Eurasia. Spectral analysis was considered as the criterion of investigation and the Holocenic cycles were analyzed considering different geochemical and biological proxies, of which seven are directly referred to vine. In this context the relation of the abovementioned proxies with spectral peaks of possible causal factors like Solar activity (SA), North Atlantic oceanic factors (Atlantic Multidecadal Oscillation - AMO and North Atlantic Oscillation - NAO), and subtropical oceanic factors (El Nino Southern Oscillation - ENSO) was also analyzed. In order to acquire a sufficiently wide number of proxies sensitive to the causal factors, we referred to a latitudinal belt wider than the one colonized by vine, also acquiring proxy from the Scandinavian area, notoriously susceptible to North Atlantic forcings. The analysis of the proxy spectral peaks, considering 20 classes with a 50-years step in the 0–1000 years range, showed that the 50% of the classes have a higher frequency of peaks at East than West, the 20% a higher frequency at West than East and the 10% an equal frequency, showing the efficiency of the propagation of Western signals towards the center of Eurasia. The search of the causal factors spectral peaks in the proxy series showed that AMO, NAO and SA acted with a certain regularity on the entire belt investigated both latitudinally and longitudinally, while spectral peaks linked to ENSO underwent a considerable attenuation moving northward. Finally, the specific analysis on viticultural proxies showed common peaks with causal factors.

In grape berries, extreme oxidative stress results in skin tissue bleaching and brownish areas appearance. Thus, these damages could negatively affect the fruit quality and the commercial value. The paper focuses on the chlorophyll roles in sunburn symptoms appearance in white skinned grape berries. In the present work, 20 cultivars were studied in three phenological stages. Berries were kept under temperature and light controlled conditions. Chlorophyll content and symptom appearance were quantified by reflectance spectroscopy indexes. The central role of radiation (and, thus, photo-oxidative damages) in berry sunburn injuries was underlined. Cultivars were classified, based on their susceptible or tolerant responses to radiation excess.