Grapevine Development Research Articles

Genome-Wide Characterization and Expression Profiling of GASA Genes during Different Stages of Seed Development in Grapevine (Vitis vinifera L.) Predict Their Involvement in Seed Development.

Members of the plant-specific GASA (gibberellic acid-stimulated Arabidopsis) gene family have multiple potential roles in plant growth and development, particularly in flower induction and seed development. However, limited information is available about the functions of these genes in fruit plants, particularly in grapes. We identified 14 GASA genes in grapevine (Vitis vinifera L.) and performed comprehensive bioinformatics and expression analyses. In the bioinformatics analysis, the locations of genes on chromosomes, physiochemical properties of proteins, protein structure, and subcellular positions were described. We evaluated GASA proteins in terms of domain structure, exon-intron distribution, motif arrangements, promoter analysis, phylogenetic, and evolutionary history. According to the results, the GASA domain is conserved in all proteins and the proteins are divided into three well-conserved subgroups. Synteny analysis proposed that segmental and tandem duplication have played a role in the expansion of the GASA gene family in grapes, and duplicated gene pairs have negative selection pressure. Most of the proteins were predicted to be in the extracellular region, chloroplasts, and the vacuole. In silico promoter analysis suggested that the GASA genes may influence different hormone signaling pathways and stress-related mechanisms. Additionally, we performed a comparison of the expression between seedless (Thompson seedless) and seeded (Red globe) cultivars in different plant parts, including the ovule during different stages of development. Furthermore, some genes were differentially expressed in different tissues, signifying their role in grapevine growth and development. Several genes (VvGASA2 and 7) showed different expression levels in later phases of seed development in Red globe and Thompson seedless, suggesting their involvement in seed development. Our study presents the first genome-wide identification and expression profiling of grapevine GASA genes and provides the basis for functional characterization of GASA genes in grapes. We surmise that this information may provide new potential resources for the molecular breeding of grapes.

Dissecting the control of shoot development in grapevine: genetics and genomics identify potential regulators

BackgroundGrapevine is a crop of major economic importance, yet little is known about the regulation of shoot development in grapevine or other perennial fruits crops. Here we combine genetic and genomic tools to identify candidate genes regulating shoot development in Vitis spp.ResultsAn F2 population from an interspecific cross between V. vinifera and V. riparia was phenotyped for shoot development traits, and three Quantitative Trait Loci (QTLs) were identified on linkage groups (LGs) 7, 14 and 18. Around 17% of the individuals exhibited a dwarfed phenotype. A transcriptomic study identified four candidate genes that were not expressed in dwarfed individuals and located within the confidence interval of the QTL on LG7. A deletion of 84,482 bp was identified in the genome of dwarfed plants, which included these four not expressed genes. One of these genes was VviCURLY LEAF (VviCLF), an orthologue of CLF, a regulator of shoot development in Arabidopsis thaliana.ConclusionsThe phenotype of the dwarfed grapevine plants was similar to that of clf mutants of A. thaliana and orthologues of the known targets of CLF in A. thaliana were differentially expressed in the dwarfed plants. This suggests that CLF, a major developmental regulator in A. thaliana, also controls shoot development in grapevine.

Evolution of Acyl-CoA-binding protein gene family in plants provides insights into potential functions of grapevine (Vitis vinifera L.)

BACKGROUND: Grapevine was one of the most important perennial fruit crops worldwide. Acyl-CoA-binding proteins (ACBPs) in eudicots and monocots show conservation in an acyl-CoA-binding domain (ACB domain) which binds acyl-CoA esters. OBJECTIVE: The information and data provided in the present study contributes to understand the evolutionary processes and potential functions of this gene family in grapevine growth and development, and responses to abiotic stress. METHODS: Using the complete grapevine genome sequences, we investigated the number grapevine ACBP genes, the exon-intron structure, phylogenetic relationships and synteny with the Arabidopsis ACBP gene family. Furthermore, the expression profiles of VvACBP genes based on public microarray data in different tissues, and the expression patterns responding to different exogenous hormones as well as abiotic and biotic stresses were presented. The qRT-PCR was used to verify the microarray data under drought stress treatments. Finally, the leaf relative water content (RWC), leaf chlorophyll content, and enzymatic activities were measured to further examine the tolerance to drought stress in grapevine. RESULTS: The six grapevine ACBPs were identified. Their distribution into various groups differed from Arabidopsis and rice. Synteny analysis demonstrated that several VvACBP genes were found in corresponding syntenic blocks of Arabidopsis, suggesting that these genes arose before the divergence of the respective lineages. Sequence alignment and structural annotation provided an overview of variations that might contribute to functional divergence from Arabidopsis ACBPs. Expressional analyses suggested that both conserved and variant biological functions exist in ACBPs across different species. The expression pattern of these genes were similar in the microarray and qRT-PCR analyses. Gene structure organization and expression characteristics of VvACBPs resembled those of their Arabidopsis orthologous, although species-specific differences also exist. Differential regulation of genes suggested functional diversification among isoforms. The biochemical and physiological data showed the tolerance to drought stress of grapevine. CONCLUSIONS: These findings provided insight into evolution of ACBP gene family in plants and a solid foundation for a deeper understanding of the complex molecular responses of grapevine to stress.

Using forced regrowth to manipulate Chardonnay grapevine (Vitis vinifera L.) development to evaluate phenological stage responses to temperature

Time and environmental conditions, such as temperature and photoperiod, are the main drivers governing grapevine development over the growing season. The most obvious growth periods in grapevines are budbreak, bloom, veraison and berry maturity. The aims of this study were to evaluate the environmental and physiological factors influencing the phenological development of Chardonnay grapevines, and to determine the best fit parameters of degree-day calculation methods for the prediction of various phenological stages. Phenological data retrieved from field vines and vines forced to regrow after heavy pruning and defoliation, whose developmental onset conditions were modified, were used to test and parameterize the degree-day calculation methods. An upper temperature threshold (TU) was optimized for the different developmental stages, and measures of the radiation use efficiency were derived to adjust TU during berry maturity. According with the candidate methods, the highest TU value coincided with bloom (29.8ºC), while the lowest was observed at veraison (20.9ºC). The RMSE of the model predictions for specific developmental stages ranged from 2 (fruit set) to 9 days (berry maturity). Modifying vine growth periods by forcing vine regrowth allowed evaluation of temperature and physiological factors that influence grapevine development.

The grapevine homeobox gene VvHB58 influences seed and fruit development through multiple hormonal signaling pathways

BackgroundThe homeobox transcription factor has a diversity of functions during plant growth and development process. Previous transcriptome analyses of seed development in grape hybrids suggested that specific homeodomain transcription factors are involved in seed development in seedless cultivars. However, the molecular mechanism of homeobox gene regulating seed development in grape is rarely reported.ResultsHere, we report that the grapevine VvHB58 gene, encoding a homeodomain-leucine zipper (HD-Zip I) transcription factor, participates in regulating fruit size and seed number. The VvHB58 gene was differentially expressed during seed development between seedless and seeded cultivars. Subcellular localization assays revealed that the VvHB58 protein was located in the nucleus. Transgenic expression of VvHB58 in tomato led to loss of apical dominance, a reduction in fruit pericarp expansion, reduced fruit size and seed number, and larger endosperm cells. Analysis of the cytosine methylation levels within the VvHB58 promoter indicated that the differential expression during seed development between seedless and seeded grapes may be caused by different transcriptional regulatory mechanisms rather than promoter DNA methylation. Measurements of five classic endogenous hormones and expression analysis of hormone-related genes between VvHB58 transgenic and nontransgenic control plants showed that expression of VvHB58 resulted in significant changes in auxin, gibberellin and ethylene signaling pathways. Additionally, several DNA methylation-related genes were expressed differentially during seed development stages in seedless and seeded grapes, suggesting changes in methylation levels during seed development may be associated with seed abortion.ConclusionVvHB58 has a potential function in regulating fruit and seed development by impacting multiple hormonal pathways. These results expand understanding of homeodomain transcription factors and potential regulatory mechanism of seed development in grapevine, and provided insights into molecular breeding for grapes.

“Flavescence dorée” impacts growth, productivity and ultrastructure of Vitis vinifera plants in Portuguese “Vinhos Verdes” region

“Flavescence dorée” (FD) is a quarantine disease associated with the presence of a phytoplasma transmitted by the insect vector Scaphoideus titanus. This disease affects grapevines and is of a great concern to the stability and sustainability of the wine industry, due to the harvest losses and death of infected plants. In Portugal, FD has seriously affected the “Vinhos Verdes” region, but so far the research on this topic is very limited. The current study confirmed that the FD phytoplasma strain involved in the outbreak in Vitis vinifera cv. Loureiro belongs to the 16SrV-D subgroup and shows very low RFLP variability in the tuf and secY genes. Transmission electron microscopy analysis of leaf midribs from infected grapevine plants revealed that the shape and structure of phloem cells were altered, presenting collapsed cells, callose accumulation in sieve plates and lipid accumulation in chloroplasts of phloem parenchyma cells. Moreover, data from two subsequent years showed that FD presence was associated with an average delay of 10 to 15 days on the time to visible inflorescences and to veraison, compared to healthy plants. At veraison, FD also lead to a significant decrease in the budburst percentage (7% to 12%), fertility index (35% in 2015), leaf area (56% to 63%), and chlorophyll content (18% to 35% lower SPAD values). Hence, infected plants showed a drastic reduction in the yield, corresponding to a decrease between 51% and 92% compared to healthy plants, which mostly resulted from a lower number of bunches (63% to 92% less), but also a decreased bunch weight (35% lower in 2015). Concerning berry quality, there were no significant differences in terms of total soluble solids and titrable acidity in both years. Here, this study concluded that the FD infection delays the grapevine development and leads to drastic production losses, which may be partly linked to the ultrastructural modifications observed in the phloem cells of infected plants.

Early Leaf Removal as a Strategy to Improve Ripening and Lower Cluster Rot in Cool Climate (Vitis vinifera L.) Pinot Grigio

Removal of basal leaves early in the vegetative and reproductive development of grapevines is a tool used to decrease fruit set, lower cluster rot severity, and improve fruit quality. However, the considerable time required for implementation limits its use by grapegrowers. Efficient mechanization can potentially mitigate these issues, albeit this practice has not yet been compared to manual application at prebloom and after-bloom stages in a cool and humid growing region where cluster rot is the major limitation for yield and fruit quality. The goal of this study was to compare mechanical leaf removal (ME) with the manual (MA) removal of six leaves at the prebloom (PB) and after-bloom (AB) phenological stages over two seasons in Pinot Grigio (a tight-clustered cultivar). Fruit set was only decreased in 2017 by MA of six basal leaves at PB (PB-MA); however, PB reduced cluster compactness in each season. The loss of fruit to gray mold was lowered by all leaf removal treatments in the drier 2017 season, but only MA treatments mitigated loss from sour rot in that year. This indicates that a clear fruit zone and reduced cluster compactness are both needed to lower the effect of cluster rot disease. Only PB treatments enhanced fruit quality, likely driven by a similar reduction in cluster compactness. The results suggest that ME at PB may be used to decrease fruit loss to gray mold in dry seasons and enhance fruit Brix. Nevertheless, PB-MA can be an effective means to reduce fruit loss to sour rot in drier seasons and enhance ripening in years with high precipitation during veraison. This information provides a single approach to alleviate two prominent issues facing seasonal management strategies in cool climate viticulture.

Conversion to organic and biodynamic viticultural practices: impact on soil, grapevine development and grape quality

Aim: The effects of integrated, organic and biodynamic management on soil quality and the growth and morphological development of Riesling grapevines were assessed during the first 4 years of a long-term field trial in Geisenheim, Germany. The overall aim was to understand the effects of these different viticultural practices on soil quality and plant morphology as the basis for product quality.Methods and results: As indicators of soil quality, earthworm abundance and the activity of selected enzymes were assessed. The vegetative and reproductive development of the grapevines, as well as their susceptibility to fungal diseases in the field, wood and grape composition, and grape yield, were investigated. Individual variables were subjected to analysis of variance. Additionally, all variables were subjected to multivariate principal component analysis. Compared with plots under integrated management, plots under the two biological treatments were characterized by higher soil quality and lower vegetative growth and grape yield, and therefore higher exposure of grapes and lower grape cluster compactness, and, probably as a result of these morphological differences, lower incidence of acetic acid rot. Principal component analysis clearly differentiated the three treatments, and showed that biodynamic management had more pronounced effects than organic management in terms of enhanced soil fertility and reduction of vegetative growth.Conclusions: In the present study, organic and especially biodynamic management resulted in a morphology favouring production of high-quality grapes. The treatments differed in terms of fertilization and plant protection methods as well as choice of cover crops. Therefore, further research is necessary with respect to root growth and the nitrogen and water uptake dynamics of vines and cover crops. The differences between grapes produced under organic and biodynamic management emphasize the need for more research on the mode of action of biodynamic preparations.Significance and impact of the study: In recent years, both winegrowers and consumers have expressed steadily growing interest in organic and especially biodynamic wine production. The present study contributes to a better understanding of the effects on grapevine growth and morphological development of shifting to these methods as a way to increase product quality.

Soil Temperature Prior to Veraison Alters Grapevine Carbon Partitioning, Xylem Sap Hormones, and Fruit Set

To gain a better understanding of environmental effects on grapevines and the physiological regulation of acclimation, we determined the effects of soil temperature (14 or 24°C) between anthesis and veraison on growth, nonstructural carbohydrates, cytokinins, abscisic acid, and leaf function of potted Vitis vinifera cv. Shiraz. Plants of each regime were selected from two groups that had been grown in a glasshouse from three weeks prior to budbreak at an average soil temperature of either 13 or 23°C. Soil temperature between anthesis and veraison affected utilization and restoration of root and trunk nonstructural carbohydrates and changes in biomass of major plant organs. Soil warming promoted shoot growth via utilization of starch reserves, while soil cooling promoted starch storage in both the root and wood and shifted overall biomass partitioning to the roots. A change in soil temperature from warm to cool through flowering was also associated with reduced fruit set. Diurnal courses of photosynthesis, transpiration, and stomatal conductance after fruit set were significantly affected by soil temperature. Phytohormones (cytokinin and abscisic acid) were measured in the xylem sap and leaves at fruit set and veraison. Differences between these two sample types during grapevine development highlight a phytohormone shift likely involved in postveraison fruit ripening. We conclude that soil temperature significantly affects grapevine growth and that the responses are mediated largely by an influence of temperature on mobilization of nonstructural carbohydrates from the roots.

Genome-Wide Analysis of the YABBY Gene Family in Grapevine and Functional Characterization of VvYABBY4.

Genes of the plant-specific YABBY transcription factor family have various roles, including lateral organ development, establishment of dorsoventral polarity, and response to abiotic stress. In this study, we carried out a genomic census of YABBY genes in grapevine (Vitis vinifera) and characterized their expression pattern during ovule development. We identified seven YABBY genes and classified them into five subfamilies, based on peptide sequence, similarity of exon–intron structure and composition of peptide sequence motifs. Analysis of YABBY gene expression in various grapevine structures and organs suggested that these genes function in diverse aspects of development and physiology. Analysis of expression during ovule development in four cultivars showed that one gene, VvYABBY4, was preferentially expressed during the period of ovule abortion in seedless cultivars. Transgenic expression of VvYABBY4 in tomato conferred reduced plant stature, dark green leaves, elongated pistil, and reduced size of fruit and seeds. Reduced seed size was associated with smaller endosperm cells. Expression of VvYABBY4 also affected expression of numerous tomato genes with presumed roles in seed development. These data suggest the potential for VvYABBY4 to influence seed development in grapevine, which may impact seedless grape breeding.

Changes in thermal resources and limitations for Georgian viticulture

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).

Efficient identification, localization and quantification of grapevine inflorescences and flowers in unprepared field images using Fully Convolutional Networks

Yield and its prediction is one of the most important tasks in grapevine breeding purposes and vineyard management. Commonly, this trait is estimated manually right before harvest by extrapolation, which mostly is labor-intensive, destructive and inaccurate. In the present study an automated image-based workflow was developed for quantifying inflorescences and single flowers in unprepared field images of grapevines, i.e. no artificial background or light was applied. It is a novel approach for non-invasive, inexpensive and objective phenotyping with high-throughput. First, image regions depicting inflorescences were identified and localized. This was done by segmenting the images into the classes inflorescence and non-inflorescence using a Fully Convolutional Network (FCN). Efficient image segmentation hereby is the most challenging step regarding the small geometry and dense distribution of single flowers (several hundred single flowers per inflorescence), similar color of all plant organs in the fore- and background as well as the circumstance that only approximately 5 % of an image show inflorescences. The trained FCN achieved a mean Intersection Over Union (IOU) of 87.6 % on the test data set. Finally, single flowers were extracted from the inflorescence-areas using Circular Hough Transform. The flower extraction achieved a recall of 80.3 % and a precision of 70.7 % using the segmentation derived by the trained FCN model. Summarized, the presented approach is a promising strategy in order to predict yield potential automatically in the earliest stage of grapevine development which is applicable for objective monitoring and evaluations of breeding material, genetic repositories or commercial vineyards.

Singular effect of soil and climate on grapevine development and berry traits in two Italian cultivars, ‘Glera’ and ‘Corvina’

Grapevine (Vitis vinifera L.) represents a particularly interesting species in terms of phenotypic plasticity, considering that the terroir, meaning the contribution of geography, geology, and climate of a certain place, together with the agronomic practices utilized, may deeply influence the berry phenotype of a particular cultivar at the physiological, molecular, and biochemical level. This phenomenon can lead to the production of wines that, although produced from the same clonal cultivar, present totally different enological profiles, and represents an issue of increasing interest not only from a biological but also from an economic point of view. The present study is aimed at a deeper understanding of the determinism of phenotypic plasticity in grapevine, trying to deconstruct the concept of terroir into two of its principal components, the soil and climate factors, and to describe the singular effect that different chemical and microbiological soil profiles, on one hand, and different geoclimatic conditions, on the other, can produce in terms of berry plasticity at the molecular, biochemical, physiological, and enological level. Here, we present preliminary results comparing physiological and phenological data in both the vegetative and reproductive phases of two grapevine cultivars, ‘Corvina’ and ‘Glera’, grown in different soils located in the same geographical location and, conversely, in the same soil under different environmental conditions. Both soil and climate strongly drove differences in vine growth and berry traits in terms of phenological development, sugar accumulation, and berry morphology. Moreover, two parameters considered in this study, sugar content and berry morphology, showed different behavior depending on the terroir factor combination (cultivar-soil-climate), and this supports the importance of a delicate balance among terroir inputs for obtaining a final product with unique characteristics.

Modelling of Wine Production Using Land Surface Temperature and FAPAR—The Case of the Douro Wine Region

The vegetative development of grapevines is orchestrated by very specific meteorological conditions. In the wine industry vineyards demand diligent monitoring, since quality and productivity are the backbone of the economic potential. Regional climate indicators and meteorological information are essential to winemakers to assure proper vineyard management. Satellite data are very useful in this process since they imply low costs and are easily accessible. This work proposes a statistical modelling approach based on parameters obtained exclusively from satellite data to simulate annual wine production. The study has been developed for the Douro Demarcated Region (DDR) due to its relevance in the winemaking industry. It is the oldest demarcated and controlled winemaking region of the world and listed as one of UNESCO’s World Heritage regions. Monthly variables associated with Land Surface Temperatures (LST) and Fraction of Absorbed Photosynthetic Active Radiation (FAPAR), which is representative of vegetation canopy health, were analysed for a 15-year period (2004 to 2018), to assess their relation to wine production. Results showed that high wine production years are associated with higher than normal FAPAR values during approximately the entire growing season and higher than normal values of surface temperature from April to August. A robust linear model was obtained using the most significant predictors, that includes FAPAR in December and maximum and mean LST values in March and July, respectively. The model explains 90% of the total variance of wine production and presents a correlation coefficient of 0.90 (after cross validation). The retained predictors’ anomalies for the investigated vegetative year (October to July) from 2017/2018 satellite data indicate that the ensuing wine production for the DDR is likely to be below normal, i.e., to be lower than what is considered a high-production year. This work highlights that is possible to estimate wine production at regional scale based solely on low-resolution remotely sensed observations that are easily accessible, free and available for numerous grapevines regions worldwide, providing a useful and easy tool to estimate wine production and agricultural monitoring.

RNA-Seq reveals new DELLA targets and regulation in transgenic GA-insensitive grapevines

BackgroundGibberellins (GAs) and their regulator DELLA are involved in many aspects of plant growth and development and most of our current knowledge in the DELLA-facilitated GA signaling was obtained from the studies of annual species. To understand GA-DELLA signaling in perennial species, we created ten GA-insensitive transgenic grapevines carrying a DELLA mutant allele (Vvgai1) in the background of Vitis vinifera ‘Thompson Seedless’ and conducted comprehensive analysis of their RNA expression profiles in the shoot, leaf and root tissues.ResultsThe transgenic lines showed varying degrees of dwarf stature and other typical DELLA mutant phenotypes tightly correlated with the levels of Vvgai1 expression. A large number of differentially expressed genes (DEGs) were identified in the shoot, leaf and root tissues of the transgenic lines and these DEGs were involved in diverse biological processes; many of the DEGs showed strong tissue specificity and about 30% them carried a DELLA motif. We further discovered unexpected expression patterns of several key flowering induction genes VvCO, VvCOL1 and VvTFL1.ConclusionsOur results not only confirmed many previous DELLA study findings in annual species, but also revealed new DELLA targets and responses in grapevine, including the roles of homeodomain transcription factors as potential co-regulators with DELLA in controlling the development of grapevine which uniquely possess both vegetative and reproductive meristems at the same time. The contrasting responses of some key flowering induction pathway genes provides new insights into the divergence of GA-DELLA regulations between annual and perennial species in GA-DELLA signaling.

“Niágara Rosada” table grape cultivated with seaweed extracts: physiological, nutritional, and yielding behavior

Adverse environmental factors, such as heat and drought stress, may impact negatively on the development of grapevines in Brazil, especially for the most important table grape variety, “Niagara Rosada.” Bioactivators from marine algae offer grower products to help overcome such environmental problems. Seaweed extracts containing organic compounds and bioactive molecules impact beneficial effects to plant physiological, nutritional, and yielding behavior. These effects can be influenced by the seaweed extract used, the methodology of production of the seaweed extracts, and the plant species. A study was carried out on a commercial field, over two seasons, aiming to evaluate the effect of foliar applications of seaweed extracts from Ascophyllum nodosum, Hypnea musciformis, Lithothamnium sp., and Sargassum vulgare at 0.6% on “Niagara Rosada” physiology, nutrition, and yield. For most evaluations, treatments with seaweed extract improved net photosynthetic rate, stomatal conductance, water use efficiency, and carboxylation efficiency. Leaf content of K, Mg, B, Cu, and Zn was positively affected by foliar application with the seaweed extracts. Yield per plant was affected by foliar application with seaweeds, with higher values in plants treated with seaweed extract from Ascophyllum nodosum followed by Lithothamnium sp.

Training systems and rootstocks on yield and agronomic performance of ‘Syrah’ grapevine in the Brazilian semiarid

ABSTRACT The Vale do São Francisco stands out among the main Brazilian wine regions, and ‘Syrah’ is a grape cultivar very important to produce red wines. The objective of this study was to evaluate the influence of training systems and rootstocks on the yield and other agronomic variables of ‘Syrah’ grapevines during eight consecutive harvests in the tropical semiarid environment in the Vale do São Francisco. An experiment was carried out in Petrolina, state of Pernambuco, with ‘Syrah’ trained to lyre and espalier systems and grafted on IAC 572, IAC 766, IAC 313, SO4, 1103 Paulsen and Harmony rootstocks. A randomized block design with four replicates and split plots was used. There was a significant interaction between the training system and rootstock for yield, number of clusters and foliar mass. The lyre system increased yield, cluster number and Ravaz index, favoring the development of more balanced grapevines. The IAC 572 rootstock promoted greater vigor by reducing yield, cluster number, bud fertility and Ravaz index. The other rootstocks were similar to each other in most variables. Net photosynthesis, stomatal conductance and instantaneous efficiency of water use were not influenced by the training system and the rootstock. The results obtained evidenced the influence of the training system associated to the rootstock on agronomic variable and yield of ‘Syrah’, recommending lyre training and grafting on 1103 Paulsen or IAC 313 in the semi-arid tropical conditions of the Vale do São Francisco.

A R2R3-MYB Transcription Factor, VvMYBC2L2, Functions as a Transcriptional Repressor of Anthocyanin Biosynthesis in Grapevine (Vitis vinifera L.).

In grapevine, the MYB transcription factors play an important role in the flavonoid pathway. Here, a R2R3-MYB transcription factor, VvMYBC2L2, isolated from Vitis vinifera cultivar Yatomi Rose, may be involved in anthocyanin biosynthesis as a transcriptional repressor. VvMYBC2L2 was shown to be a nuclear protein. The gene was shown to be strongly expressed in root, flower and seed tissue, but weakly expressed during the fruit development in grapevine. Overexpressing the VvMYBC2L2 gene in tobacco resulted in a very marked decrease in petal anthocyanin concentration. Expression analysis of flavonoid biosynthesis structural genes revealed that chalcone synthase (CHS), dihydroflavonol 4-reductase (DFR), leucoanthocyanidin reductase (LAR) and UDP glucose flavonoid 3-O-glucosyl transferase (UFGT) were strongly down-regulated in the VvMYBC2L2-overexpressed tobacco. In addition, transcription of the regulatory genes AN1a and AN1b was completely suppressed in transgenic plants. These results suggested that VvMYBC2L2 plays a role as a negative regulator of anthocyanin biosynthesis.

Temperature-based zoning of the Bordeaux wine region

Temperature is a driving climate variable for grapevine development and grape ripening kinetics. The current study first reports interpolation of daily minimum and maximum temperature data by a weather station network from 2001 to 2005 in the Bordeaux (France) region by means of regression kriging using terrain, satellite and land-cover derived covariates. Second it analyses the interpolation procedure errors in agroclimatic indices by means of cross validation and then it compares the field observations of grapevine phenology to temperature-based predicted phenology applied to interpolated data. Finally it proposes a simple method to perform a zoning of Bordeaux vineyards based upon the spatialized prediction of the day on which grape sugar content reaches 200 g.L-1. The zoning performed shows large potential differences in grape maturity date (up to 20 days) induced by temperature spatial variability in a low relief area.

Assessment of the impact of PS3-induced resistance to downy mildew on grapevine physiology

Elicitor-induced resistance against diseases is an attractive strategy that could contribute to reduce the use of fungicides for plant protection. However, activation of defenses has an energetic cost that plants have to fuel by a mobilization of their primary metabolism with possible adverse effect on their physiology. In this context, this study was performed to determine whether elicitor-induced resistance of grapevine leaves against downy mildew impacted its development and metabolism. The elicitor PS3 (sulfated β-glucan laminarin) was sprayed on grapevine herbaceous cuttings grown in greenhouses once or three times, and its impact was studied on young and older grapevine leaves, prior to, and after Plasmopara viticola inoculation.PS3 did not affect grapevine development during the time course of the experiment. A metabolomic analysis, mainly focused on primary metabolites, highlighted a leaf age dependent effect of PS3 treatment. Nitrogen compounds, and sugars to a lesser extent, were impacted.The results obtained complete the current knowledge of the impact of elicitor-induced resistance on plant physiology. They will be helpful to guide further experiments required to better determine the costs and benefits of elicitor-induced resistance in plants.