Ecophysiologie et Génomique Fonctionnelle de la Vigne

The natural environment for plants is composed of a complex set of abiotic stresses and biotic stresses. Plant responses to these stresses are equally complex. Systems biology approaches facilitate a multi-targeted approach by allowing one to identify regulatory hubs in complex networks. Systems biology takes the molecular parts (transcripts, proteins and metabolites) of an organism and attempts to fit them into functional networks or models designed to describe and predict the dynamic activities of that organism in different environments. In this review, research progress in plant responses to abiotic stresses is summarized from the physiological level to the molecular level. New insights obtained from the integration of omics datasets are highlighted. Gaps in our knowledge are identified, providing additional focus areas for crop improvement research in the future.

Flavonoids are secondary metabolites involved in several aspects of plant development and defence. They colour fruits and flowers, favouring seed and pollen dispersal, and contribute to plant adaptation to environmental conditions such as cold or UV stresses, and pathogen attacks. Because they affect the quality of flowers (for horticulture), fruits and vegetables, and their derivatives (colour, aroma, stringency, etc.), flavonoids have a high economic value. Furthermore, these compounds possess pharmaceutical properties extremely attractive for human health. Thanks to easily detectable mutant phenotypes, such as modification of petal pigmentation and seeds exhibiting transparent testa, the enzymes involved in the flavonoid biosynthetic pathway have been characterized in several plant species. Conserved features as well as specific differences have been described. Regulation of structural gene expression appears tightly organized in a spatial and temporal way during plant development, and is orchestrated by a ternary complex involving transcription factors from the R2R3-MYB, basic helix-loop-helix (bHLH), and WD40 classes. This MYB-bHLH-WD40 (MBW) complex regulates the genes that encode enzymes specifically involved in the late steps of the pathway leading to the biosynthesis of anthocyanins and condensed tannins. Although several genes encoding transcription factors from these three families have been identified, many gaps remain in our understanding of the regulation of this biosynthetic pathway, especially about the respective roles of bHLH and WD40 proteins. A better knowledge of the regulatory mechanisms of the flavonoid pathway is likely to favour the development of new biotechnological tools for the generation of value-added plants with optimized flavonoid content.

Legumes played central roles in the development of agriculture and civilization, and today account for approximately one-third of the world's primary crop production. Unfortunately, most cultivated legumes are poor model systems for genomic research. Therefore, Medicago truncatula, which has a relatively small diploid genome, has been adopted as a model species for legume genomics. To enhance its value as a model, we have generated a gene expression atlas that provides a global view of gene expression in all major organ systems of this species, with special emphasis on nodule and seed development. The atlas reveals massive differences in gene expression between organs that are accompanied by changes in the expression of key regulatory genes, such as transcription factor genes, which presumably orchestrate genetic reprogramming during development and differentiation. Interestingly, many legume-specific genes are preferentially expressed in nitrogen-fixing nodules, indicating that evolution endowed them with special roles in this unique and important organ. Comparative transcriptome analysis of Medicago versus Arabidopsis revealed significant divergence in developmental expression profiles of orthologous genes, which indicates that phylogenetic analysis alone is insufficient to predict the function of orthologs in different species. The data presented here represent an unparalleled resource for legume functional genomics, which will accelerate discoveries in legume biology.

Wine is made up of more than one thousand compounds, the majority of which, such as vitamins and minerals, come from the grapes, while others, like ethanol and glycerol, are products of the winemaking process. Although sugars are either partially or completely transformed, sugar import and accumulation into the ripening berry is a major parameter of wine quality. Sugar status is directly related to the final alcoholic content of wine, and regulates several genes responsible for the development of its aromatic and organoleptic properties. Physiological ripeness is reached when the grapes achieve sufficiently high sugar levels without loosing too much acidity; however, aromatic and phenolic compound content must also be taken into account. Softening and water content are other essential characteristics of a ripe berry. From a winemaker point of view, optimal grape maturity is essential for wine quality, but is difficult to assess because it is under multifactorial control, involving grapevine cultivar variety and environmental parameters such as soil, temperature, exposure to sun, and hormonal regulation. Continued study of the key control points in grape ripening is crucial if we ultimately hope to improve grape and wine quality.

Abstract Climate change is a major challenge in wine production. Temperatures are increasing worldwide, and most regions are exposed to water deficits more frequently. Higher temperatures trigger advanced phenology. This shifts the ripening phase to warmer periods in the summer, which will affect grape composition, in particular with respect to aroma compounds. Increased water stress reduces yields and modifies fruit composition. The frequency of extreme climatic events (hail, flooding) is likely to increase. Depending on the region and the amount of change, this may have positive or negative implications on wine quality. Adaptation strategies are needed to continue to produce high-quality wines and to preserve their typicity according to their origin in a changing climate. The choice of plant material is a valuable resource to implement these strategies. (JEL Classifications: Q13, Q54)

Among the dramatic changes occurring during grape berry (Vitis vinifera) development, those affecting the flavonoid pathway have provoked a number of investigations in the last 10 years. In addition to producing several compounds involved in the protection of the berry and the dissemination of the seeds, final products of this pathway also play a critical role in berry and wine quality. In this article, we describe the cloning and functional characterization of VvMYB5b, a cDNA isolated from a grape berry (V. vinifera 'Cabernet Sauvignon') library. VvMYB5b encodes a protein belonging to the R2R3-MYB family of transcription factors and displays significant similarity with VvMYB5a, another MYB factor recently shown to regulate flavonoid synthesis in grapevine. The ability of VvMYB5a and VvMYB5b to activate the grapevine promoters of several structural genes of the flavonoid pathway was confirmed by transient expression of the corresponding cDNAs in grape cells. Overexpression of VvMYB5b in tobacco (Nicotiana tabacum) leads to an up-regulation of genes encoding enzymes of the flavonoid pathway and results in the accumulation of anthocyanin- and proanthocyanidin-derived compounds. The ability of VvMYB5b to regulate particularly the anthocyanin and the proanthocyanidin pathways is discussed in relation to other recently characterized MYB transcription factors in grapevine. Taken together, data presented in this article give insight into the transcriptional mechanisms associated with the regulation of the flavonoid pathway throughout grape berry development.

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<p style="text-align: justify;"><strong>Aims</strong>: The impact of water deficit stress on vine shoot growth, berry weight, grape composition and overall vintage quality was investigated in Bordeaux vineyards. Methods for assessing water deficit stress were compared.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Vine water status was assessed on three soil types during four vintages by means of stem water potential and carbon isotope discrimination measured on grape sugar. Regional water deficit was compared for a range of over 30 vintages by means of water balance modelling. It was shown that water deficit stress anticipated shoot growth slackening, limited berry weight and enhanced berry anthocyanin content. Berry sugar content was greatest when water deficit was mild. It was shown that stem water potential measurements and carbon isotope discrimination are accurate tools for assessing vine water status at plot scale. Seasonal water deficit at a regional scale can be correctly estimated by water balance models. Vintage quality in Bordeaux is determined by the intensity of water deficit stress rather than by the level of the temperatures.</p><p style="text-align: justify;"><strong>Conclusions</strong>: Vine phenology and grape ripening are highly dependent on water uptake conditions. Mild water deficit stress enhances grape quality for the production of red wines. Vine water status can accurately be assessed by means of stem water potential or carbon isotope discrimination measured on grape sugars. Quality losses through severe water stress can be avoided through the use of drought-adapted plant material, appropriate canopy management, yield reduction or the implementation of deficit irrigation.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: This study shows the key role of water deficits in the production of quality grapes for red wine production. Methods for assessing vine water status are compared and discussed. Among many existing methods, the accuracy of stem water potential, carbon isotope discrimination measured on grape sugar and water balance modelling are emphasized.</p>

Climate change will impose increasingly warm and dry conditions on vineyards. Wine quality and yield are strongly influenced by climatic conditions and depend on complex interactions between temperatures, water availability, plant material, and viticultural techniques. In established winegrowing regions, growers have optimized yield and quality by choosing plant material and viticultural techniques according to local climatic conditions, but as the climate changes, these will need to be adjusted. Adaptations to higher temperatures include changing plant material (e.g., rootstocks, cultivars and clones) and modifying viticultural techniques (e.g., changing trunk height, leaf area to fruit weight ratio, timing of pruning) such that harvest dates are maintained in the optimal period at the end of September or early October in the Northern Hemisphere. Vineyards can be made more resilient to drought by planting drought resistant plant material, modifying training systems (e.g., goblet bush vines, or trellised vineyards at wider row spacing), or selecting soils with greater soil water holding capacity. While most vineyards in Europe are currently dry-farmed, irrigation may also be an option to grow sustainable yields under increasingly dry conditions but consideration must be given to associated impacts on water resources and the environment.

The arbuscular mycorrhizal fungus Glomus mosseae is able to confer bioprotection against Phytophthora parasitica in tomato roots. Localized and induced systemic resistance (ISR) have been demonstrated to be involved in pathogen control in mycorrhizal and nonmycorrhizal roots with a split root experimental system. Decreased pathogen development in mycorrhizal and nonmycorrhizal parts of mycorrhizal root systems is associated with accumulation of phenolics and plant cell defense responses. G. mosseae-containing cortical cells in the mycorrhizal tissues are immune to the pathogen and exhibit a localized resistance response with the formation of cell wall appositions reinforced by callose adjacent to intercellular hyphae. The systemically induced resistance in nonmycorrhizal root parts is characterized by elicitation of host wall thickenings containing non-esterified pectins and PR-1a protein in reaction to intercellular pathogen hyphae, and by the formation of callose-rich encasement material around P. parasitica hyphae that are penetrating root cells. PR-la protein is detected in the pathogen wall only in these tissues. None of these cell reactions are observed in nonmycorrhizal pathogen-infected root systems, where disease development leads to host cell death. The cellular and molecular basis of bioprotection by an arbuscular mycorrhizal fungus is discussed in relation to that induced by other nonpathogenic microorganisms.

Water availability is arguably the most important environmental factor limiting crop growth and productivity. Erratic precipitation patterns and increased temperatures resulting from climate change will likely make drought events more frequent in many regions, increasing the demand on freshwater resources and creating major challenges for agriculture. Addressing these challenges through increased irrigation is not always a sustainable solution so there is a growing need to identify and/or breed drought-tolerant crop varieties in order to maintain sustainability in the context of climate change. Grapevine (Vitis vinifera), a major fruit crop of economic importance, has emerged as a model perennial fruit crop for the study of drought tolerance. This review synthesizes the most recent results on grapevine drought responses, the impact of water deficit on fruit yield and composition, and the identification of drought-tolerant varieties. Given the existing gaps in our knowledge of the mechanisms underlying grapevine drought responses, we aim to answer the following question: how can we move towards a more integrative definition of grapevine drought tolerance?

International audience

Abstract The lack of information on the ways seasonal drought modifies the CO 2 exchange between Neotropical rainforest ecosystems and the atmosphere and the resulting carbon balance hinders our ability to precisely predict how these ecosystems will respond as global environmental changes force them to face increasingly contrasting conditions in the future. To address this issue, seasonal variations in daily net ecosystem productivity (NEP d ) and two main components of this productivity, daily total ecosystem respiration ( R Ed ) and daily gross ecosystem productivity (GEP d ), were estimated over 2 years at a flux tower site in French Guiana, South America (5 °16′54″N, 52 °54′44″W). We compared seasonal variations between wet and dry periods and between dry periods of contrasting levels of intensity (i.e. mild vs. severe) during equivalent 93‐day periods. During the wet periods, the ecosystem was almost in balance with the atmosphere (storage of 9.0 g C m −2 ). Seasonal dry periods, regardless of their severity, are associated with higher incident radiation and lower R Ed combined with reduced soil respiration associated with low soil water availability. During the mild dry period, as is normally the case in this region, the amount of carbon stored in the ecosystem was 32.7 g C m −2 . Severe drought conditions resulted in even lower R Ed , whereas the photosynthetic activity was only moderately reduced and no change in canopy structure was observed. Thus, the severe dry period was characterized by greater carbon storage (64.6 g C m −2 ), emphasizing that environmental conditions, such as during a severe drought, modify the CO 2 exchange between Neotropical rainforest ecosystems and the atmosphere and potentially the resulting carbon balance.

Report of 1993 activities*INRA, centre de Dijon Diffusion du document : INRA, centre de Dijon

We elucidate grapevine evolution and domestication histories with 3525 cultivated and wild accessions worldwide. In the Pleistocene, harsh climate drove the separation of wild grape ecotypes caused by continuous habitat fragmentation. Then, domestication occurred concurrently about 11,000 years ago in Western Asia and the Caucasus to yield table and wine grapevines. The Western Asia domesticates dispersed into Europe with early farmers, introgressed with ancient wild western ecotypes, and subsequently diversified along human migration trails into muscat and unique western wine grape ancestries by the late Neolithic. Analyses of domestication traits also reveal new insights into selection for berry palatability, hermaphroditism, muscat flavor, and berry skin color. These data demonstrate the role of the grapevines in the early inception of agriculture across Eurasia.

Aim: Major effects of climate change are an increase in temperature, a modification in rainfall patterns and an increase in incoming radiations, in particular UV-Bs. Grapevines are highly sensitive to climatic conditions. Hence, plant development, grape ripening and grape composition at ripeness are modified by climate change. Some of these changes are already visible and will be amplified over the coming decades; other effects, although not yet measurable, can be predicted by modeling. The objective of this paper is to assess which modifications in wine quality and typicity can be expected and what levers growers can implement to adapt to this changing situation. Methods and results: This paper focusses on the effect of temperature, vine water status and UV-B radiation in viticulture. Vine phenology is driven by temperacture. A significant advance in phenology (i.e. budburst, flowering and veraison dates) has been observed since the early 1980’s in most winegrowing regions. The combined effect of advanced phenology and increased temperatures results in warmer conditions during grape ripening. In these conditions, grapes contain more sugar and less organic acids. Composition in secondary metabolites, and in particular aromas and aroma precursors, is dramatically changed. Increased drought, because of lower summer rain and/or because of higher reference evapotranspiration (ET0), induces earlier shoot growth cessation, reduced berry size, increased content in skin phenolic compounds, lower malic acid concentrations and modified aroma and aroma precursor profiles. Increased UV-B radiation enhances the accumulation of skin phenolics and modifies aroma and aroma precursor profiles. Over the next decades, an amplification of these trends is highly likely. Major adaptations can be reached though modifications in plant material (grapevine varieties, clones and root stocks), vineyard management techniques (grapevine architecture, canopy management, harvest dates, vineyard floor management, timing of harvest, irrigation) or site selection (altitude, aspect, soil water holding capacity). Conclusion: Climate change will induce changes in grape composition which will modify wine quality and typicity. However, these modifications can be limited through adaptations in the vineyard.Significance and impact of the study: This study assesses the impact of major climatic parameters (temperature, water and radiation) on vine physiology and grape ripening. It addresses the issue of how the expected changes under climate change will impact viticulture. It is shown that appropriate levers do exist to allow growers to adapt to this new situation. Among these, modifications in plant material and viticultural techniques are the most promising tools.

Berry fresh weight and composition are under the control of complex interactions among genotype, environmental factors, and viticulture practice, which all affect not only the mean value but also the ranges of variation in berry traits. Both mean values and variation range in berry composition play a role in berry quality and, subsequently, wine typicity. This review examines recent ecophysiological, genetic, and molecular knowledge to provide better understanding of the mechanisms that influence variability in berry weight and composition. We specifically reviewed the variation range in berry weight and composition (including sugars, organic acids, and anthocyanins) among Vitis genotypes, the environmental and viticulture practices that cause variability for a given cultivar, the genetic clues underlying the genotypic variation, and the putative genes controlling berry weight and composition. Despite numerous studies comparing differences in the mean value of a berry trait among different environment conditions and viticulture practices, very few studies have explored the level of variation in response to those factors. Present genetic and molecular studies are mainly focused on identifying genes involved in the control of berry weight and composition, with few considerations of environmental factors that affect their expression. In the future, more effort should be directed toward integration of genetic and molecular work with ecophysiological approaches in an effort to gain novel insights into the cause of variability in grape fresh weight and composition.

Climate change is affecting grape yield, composition and wine quality. As a result, the geography of wine production is changing. In this Review, we discuss the consequences of changing temperature, precipitation, humidity, radiation and CO2 on global wine production and explore adaptation strategies. Current winegrowing regions are primarily located at mid-latitudes (California, USA; southern France; northern Spain and Italy; Barossa, Australia; Stellenbosch, South Africa; and Mendoza, Argentina, among others), where the climate is warm enough to allow grape ripening, but without excessive heat, and relatively dry to avoid strong disease pressure. About 90% of traditional wine regions in coastal and lowland regions of Spain, Italy, Greece and southern California could be at risk of disappearing by the end of the century because of excessive drought and more frequent heatwaves with climate change. Warmer temperatures might increase suitability for other regions (Washington State, Oregon, Tasmania, northern France) and are driving the emergence of new wine regions, like the southern United Kingdom. The degree of these changes in suitability strongly depends on the level of temperature rise. Existing producers can adapt to a certain level of warming by changing plant material (varieties and rootstocks), training systems and vineyard management. However, these adaptations might not be enough to maintain economically viable wine production in all areas. Future research should aim to assess the economic impact of climate change adaptation strategies applied at large scale. Grapes produced for winemaking are highly susceptible to changes in climate, particularly extreme heat and drought. This Review examines the changing geography of existing and emerging winegrowing regions, and recommends adaptation measures to increasing heat and modified drought, pest and disease pressure.

Agrobiodiversity—the variation within agricultural plants, animals, and practices—is often suggested as a way to mitigate the negative impacts of climate change on crops [S. A. Wood et al. , Trends Ecol. Evol. 30, 531–539 (2015)]. Recently, increasing research and attention has focused on exploiting the intraspecific genetic variation within a crop [Hajjar et al. , Agric. Ecosyst. Environ. 123, 261–270 (2008)], despite few relevant tests of how this diversity modifies agricultural forecasts. Here, we quantify how intraspecific diversity, via cultivars, changes global projections of growing areas. We focus on a crop that spans diverse climates, has the necessary records, and is clearly impacted by climate change: winegrapes (predominantly Vitis vinifera subspecies vinifera ). We draw on long-term French records to extrapolate globally for 11 cultivars (varieties) with high diversity in a key trait for climate change adaptation—phenology. We compared scenarios where growers shift to more climatically suitable cultivars as the climate warms or do not change cultivars. We find that cultivar diversity more than halved projected losses of current winegrowing areas under a 2 °C warming scenario, decreasing areas lost from 56 to 24%. These benefits are more muted at higher warming scenarios, reducing areas lost by a third at 4 °C (85% versus 58%). Our results support the potential of in situ shifting of cultivars to adapt agriculture to climate change—including in major winegrowing regions—as long as efforts to avoid higher warming scenarios are successful.

A “terroir” is a cultivated ecosystem in which the vine interacts with the soil and the climate. The soil influences vine development and grape ripening through soil temperature, water supply and mineral supply. Soil temperature has a significant effect on vine phenology. Limited water supply to the vines restricts shoot and berry growth, which is critical for reaching a suitable grape composition to produce high-quality red wines. Secondary metabolites, like polyphenols (anthocyanins, tannins) and aroma compounds or their precursors, are impacted in particular by vine water status. Among nutrients vines pick up from the soil, nitrogen plays a key role. Nitrogen influences vine vigor, yield, berry size and grape composition. Low nitrogen supply stimulates the synthesis of polyphenols, while it can negatively impact certain aroma compounds in grapes and wines. Over the past decades, tools have been developed to quantify terroir parameters. Vine water status can be assessed by means of carbon isotope discrimination measured on grape sugar (so-called δ13C). Vine nitrogen status can be assessed with the measurement of Yeast Available Nitrogen (YAN). In this way, terroir parameters can not only be measured but also mapped. Ideally, vineyards should be established in areas where soil temperature (relative to air temperature), soil water holding capacity (relative to rainfall and potential evapotranspiration) and soil nitrogen availability are optimum for the type of wine which is intended to be produced. Terroir expression can, however, be optimized by choosing appropriate plant material, and via vineyard floor management, fertilization and other management techniques.