Iron (Fe) deficiency-induced chlorosis is a major nutritional disorder in crops growing in calcareous soils. Iron deficiency in fruit tree crops causes chlorosis, decreases in vegetative growth and marked fruit yield and quality losses. Therefore, Fe fertilizers, either applied to the soil or delivered to the foliage, are used every year to control Fe deficiency in these crops. On the other hand, a substantial body of knowledge is available on the fundamentals of Fe uptake, long and short distance Fe transport and subcellular Fe allocation in plants. Most of this basic knowledge, however, applies only to Fe deficiency, with studies involving Fe fertilization (i.e., with Fe-deficient plants resupplied with Fe) being still scarce. This paper reviews recent developments in Fe-fertilizer research and the state-of-the-art of the knowledge on Fe acquisition, transport and utilization in plants. Also, the effects of Fe-fertilization on the plant responses to Fe deficiency are reviewed. Agronomical Fe-fertilization practices should benefit from the basic knowledge on plant Fe homeostasis already available; this should be considered as a long-term goal that can optimize fertilizer inputs, reduce grower's costs and minimize the environmental impact of fertilization.

Towards a knowledge-based correction of iron chlorosis

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.

https://www.mdpi.com/2073-4395/9/9/514/pdf

An Update on the Impact of Climate Change in Viticulture and Potential Adaptations

Controlling stomatal aperture in semi-arid regions-The dilemma of saving water or being cool?

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.

/pdf/modified-grape-composition-under-climate-change-conditions-1lb5n7flkz.pdf

Modified grape composition under climate change conditions requires adaptations in the vineyard

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.

/pdf/soil-related-terroir-factors-a-review-35yl9pz5ev.pdf

Soil-related terroir factors: a review

Grapes are a widely cultivated and economically important crop. Climate change is increasing the focus and investment on the development of more drought resistant varieties. However, markets often dictate specific grape varieties that can be grown and sold. Thus growers are increasingly interested in conferring particular traits of interest (e.g., drought tolerance) through grafting onto rootstocks. A major goal is to develop rootstocks that can influence scion growth and productivity under drought; particularly those that can increase water conservation through reducing the need for irrigation while ameliorating negative impacts on yields. Growers and scientists recognize that rootstocks have a profound influence on vine physiology (e.g., stomatal conductance, photosynthesis, water status), productivity (e.g., growth, fruit yields, fruit composition), and drought resistance. The challenge is to better understand the exact mechanisms through which rootstocks manifest these effects and thus build the knowledge necessary to drive the development of rootstocks with predictable effects on the scion. The aim of this review is to explore our current understanding of the mechanisms by which grapevine rootstocks influence scion growth and stress response; specifically focused on the integration of vine growth and productivity under water deficit.

The influence of grapevine rootstocks on scion growth and drought resistance

Rootstocks as a component of adaptation to environment

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

/pdf/aba-mediated-responses-to-water-deficit-separate-grapevine-53bju6dm89.pdf

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

Aims: Water scarcity, associated with climate change, is a particular threat to the sustainability of viticulture in present areas of cultivation, usually prone to drought Breeding grapevine for reduced water use, better water extraction and maintained production (ie, high water use efficiency) is therefore of major interestMethods and results: This requires a comprehensive knowledge of the physiological impacts of drought on yield and quality Attention should be paid to those mechanisms involved in the regulation of water status in plant tissues, as it is the primary parameter affected by drought Transpiration rate, which has a major influence on plant water status, should therefore receive special attention in breeding programs Beyond scions, the role of rootstocks, which have been largely introduced in vineyards, should be investigated further as it determines water extraction capacity and could modify water balance in grafted plantsConclusion: Here we review recent advances in the characterization of genetic variability in the control of water use and water status, whether induced by rootstock or scionSignificance and impact of the study: This review should help scientists in choosing the relevant physiological targets in their research on grapevine tolerance to drought, whether for breeding prospects or new management practices

/pdf/adapting-plant-material-to-face-water-stress-in-vineyards-1k1tlfaxw9.pdf

Landry Rossdeutsch

Papers

The influence of grapevine rootstocks on scion growth and drought resistance

Rootstocks as a component of adaptation to environment

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

Adapting plant material to face water stress in vineyards: which physiological targets for an optimal control of plant water status?