Grapevine Roots Research Articles

First Report of Fusarium commune Associated with a Root Rot of Grapevine in China.

During last decade, species belonging to Fusarium, Rosellinia, Armillaria and Dactylonectria were confirmed as phytopathogens causing grapevine root diseases (Highet and Nair 1995; Teixeira et al. 1995; Calamit et al. 2021; Ye et al. 2021). From 2020 to 2021, grapevine decline was observed in several vineyards in Beijing region, China. Leaves turned yellow with brown necrotic patches and roots were poorly developed, which was suggesting that a root disease was affecting the vines. The disease incidence was up to 10-15% of the vineyard for sample collection. Symptomatic root samples (cv. 'Red Globe') were collected and tissue fragments were excised at the margin of the symptomatic tissue in order to isolate the potential pathogen. The surface was sterilized using 1.5% sodium hypochlorite for 3 min, followed by 70% ethanol for 30 sec, and rinsed three times with sterile distilled water (Ye et al. 2020). Tissues were dried and placed onto potato dextrose agar (PDA) plates, followed by incubation at 25°C under dark conditions for 3 d. Hyphal tips of fungi growing from the samples were transferred onto new PDA plates and incubated until they produced conidia. Next, single spores were transferred onto new PDA plates and incubated at 25°C for 7 d. Eight isolates numbered with JZB3110172 to JZB3110179 were obtained and their culture characters were identical, and the re-isolation percentage was 100%. Colonies were white to orange, with abundant fluffy aerial mycelium. Macroconidia were fusiform with a slightly curved apical cell and a foot-shaped basal cell, and measured 16.2-43.2 μm × 2.7-4.9 μm (n=50); microconidia were cylindrical, straight to slightly curved, 5.1-13 × 2.1-3.9 μm (n=50). Morphological characters of the isolates resembled to Fusarium commune (Skovgaard et al. 2003). For phylogenetic analysis, genomic DNA of the eight isolates was extracted with a DNA extraction kit (DNeasy plant Mini Kit). PCR amplifications of two phylogenetic markers (EF-1α and RPB2) were performed using the primers EF-1/EF-2 (Geiser et al. 2004) and RPB2-5F2/RPB2-7cR (Liu et al. 1995), respectively. The sequences were deposited in GenBank ON457645 to ON457660. Comparison of base pairs on Maximum likelihood (ML) phylogenetic analysis was conducted using the RAxML-HPC2 tool on XSEDE on the CIPRES Science Gateway platform (http://www.phylo.org/). The sequences of EF-1α and RPB2 of the eight isolates showed 99 to 100% similarity to the reference isolates of F. commune. In the phylogenetic tree, the isolates from this study clustered with the representative strains of F. commune (NRRL 52764, NRRL 28387 and NRRL 52744). Based on morphological characters and the phylogenetic results, all of isolates were identified as F. commune. Koch's postulates were conducted on healthy, 3-month-old grapevine 'Marselan'. Plant roots were trimmed with sterile scissors and then soaked in a spore suspension (1.0 × 106 spores mL-1) or sterile water (as the control) for 30 min. The inoculated grapevines were transplanted into pots and kept in the greenhouse at 25°C. After 14 days, all the inoculated plants developed necrosis and turned yellow. No symptoms were observed on the control. Koch's postulates were fulfilled by re-isolating the fungus from necrotic root tissues. The isolates obtained from the artificially infected tissue were identified again as F. commune based on morphological and molecular analyses. Overall, this is the first report of F. commune associated with a grapevine root rot globally, which lays a foundation for further study and developing disease control methods.

Towards grapevine root architectural models to adapt viticulture to drought.

To sustainably adapt viticultural production to drought, the planting of rootstock genotypes adapted to a changing climate is a promising means. Rootstocks contribute to the regulation of scion vigor and water consumption, modulate scion phenological development and determine resource availability by root system architecture development. There is, however, a lack of knowledge on spatio-temporal root system development of rootstock genotypes and its interactions with environment and management that prevents efficient knowledge transfer into practice. Hence, winegrowers take only limited advantage of the large variability of existing rootstock genotypes. Models of vineyard water balance combined with root architectural models, using both static and dynamic representations of the root system, seem promising tools to match rootstock genotypes to frequently occurring future drought stress scenarios and address scientific knowledge gaps. In this perspective, we discuss how current developments in vineyard water balance modeling may provide the background for a better understanding of the interplay of rootstock genotypes, environment and management. We argue that root architecture traits are key drivers of this interplay, but our knowledge on rootstock architectures in the field remains limited both qualitatively and quantitatively. We propose phenotyping methods to help close current knowledge gaps and discuss approaches to integrate phenotyping data into different models to advance our understanding of rootstock x environment x management interactions and predict rootstock genotype performance in a changing climate. This could also provide a valuable basis for optimizing breeding efforts to develop new grapevine rootstock cultivars with optimal trait configurations for future growing conditions.

Antifungal Activities of a Grapevine Byproduct Extract Enriched in Complex Stilbenes and Stilbenes Metabolization by Botrytis cinerea

Grapevine co-products, as canes, represent a source of compounds of interest to control vineyard diseases with a sustainable approach. We chose to study an extract that we produced from grapevine trunk and roots. This extract, enriched in complex stilbenes, strongly reduced mycelial growth and spore germination of Botrytis cinerea, the fungal agent causing gray mold. The most active stilbenes were resveratrol, r-viniferin, and ε-viniferin. This grapevine extract also inhibited the production of Botrytis laccases. Conversely, Botrytis secretome metabolized resveratrol into δ-viniferin and pallidol (2 dimers); and ε-viniferin, a dimer, into hopeaphenol, r-viniferin, and r2-viniferin (3 tetramers). r-Viniferin and hopeaphenol (2 tetramers) were not metabolized. The biotransformed extract maintained an effective antimycelial activity. This study provides evidence that a grapevine extract enriched in oligomerized stilbenes exerts different anti-Botrytis activities, notwithstanding the ability of the fungus to metabolize some stilbenes.

Nitrogen control of transpiration in grapevine.

Transpiration per unit of leaf area is the end-product of the root-to-leaf water transport within the plant, and it is regulated by a series of morpho-physiological resistances and hierarchical signals. The rate of water transpired sustains a series of processes such as nutrient absorption and leaf evaporative cooling, with stomata being the end-valves that maintain the optimal water loss under specific degrees of evaporative demand and soil moisture conditions. Previous work provided evidence of a partial modulation of water flux following nitrogen availability linking high nitrate availability with tight stomatal control of transpiration in several species. In this work, we tested the hypothesis that stomatal control of transpiration, among others signals, is partially modulated by soil nitrate ( ) availability in grapevine, with reduced availability (alkaline soil pH, reduced fertilization, and distancing source) associated with decreased water-use efficiency and higher transpiration. We observed a general trend when was limiting with plants increasing either stomatal conductance or root-shoot ratio in four independent experiments with strong associations between leaf water status, stomatal behavior, root aquaporins expression, and xylem sap pH. Carbon and oxygen isotopic signatures confirm the proximal measurements, suggesting the robustness of the signal that persists over weeks and under different gradients of availability and leaf nitrogen content. Nighttime stomatal conductance was unaffected by manipulation treatments, while application of high vapor pressure deficit conditions nullifies the differences between treatments. Genotypic variation for transpiration increase under limited availability was observed between rootstocks indicating that breeding (e.g., for high soil pH tolerance) unintentionally selected for enhanced mass flow nutrient acquisition under restrictive or nutrient-buffered conditions. We provide evidence of a series of specific traits modulated by availability and suggest that fertilization is a potential candidate for optimizing grapevine water-use efficiency and root exploration under the climate-change scenario.

Nematicidal Activity of a Garlic Extract Formulation against the Grapevine Nematode Xiphinema index.

The nematicidal activity of garlic extracts is known on root-knot nematodes but never investigated on the grapevine nematode Xiphinema index. In this study, the nematicidal activity of a commercial garlic extract formulate (GEF) was assessed on X. index, both in vitro and in a pot assay. In the in vitro assays, mixed specimens of X. index were exposed to a 0-4 mL L-1 range of GEF concentrations, checking nematode immotility and mortality after 2, 4 or 8 h. In the experiments on potted grapevines, plants cultivated in soil infested by X. index were irrigated twice at a 15-day interval with 0.05, 0.2 and 0.5 mL L-1 solutions of GEF, including nontreated soil as a control. An almost complete mortality of X. index specimens occurred after a 2 h exposure to a 2 mL L-1 GEF concentration, while an 8 h exposure to even the 0.0312 and 0.0156 mL L-1 solutions resulted in about 50% and 30% mortality, respectively. Soil treatment with a 0.5 mL L-1 GEF solution significantly reduced the population of X. index and increased the grapevine root growth compared to nontreated soil or soil treated with the lower dosages. Results of this study indicated that garlic-based nematicides could be an effective tool for X. index management in organic and integrated vineyards.

Genetic analysis of grapevine root system architecture and loci associated gene networks.

Own-rooted grapevines and grapevine rootstocks are vegetatively propagated from cuttings and have an adventitious root system. Unraveling the genetic underpinnings of the adventitious root system architecture (RSA) is important for improving own-rooted and grafted grapevine sustainability for a changing climate. Grapevine RSA genetic analysis was conducted in an Vitis sp. 'VRS-F2' population. Nine root morphology, three total root system morphology, and two biomass traits that contribute to root anchorage and water and nutrient uptake were phenotyped. Quantitative trait loci (QTL) analysis was performed using a high density integrated GBS and rhAmpSeq genetic map. Thirty-one QTL were detected for eleven of the RSA traits (surface area, root volume, total root length, fresh weight, number of tips, forks or links, longest root and average root diameter, link length, and link surface area) revealing many small effects. Several QTL were colocated on chromosomes 1, 9, 13, 18, and 19. QTL with identical peak positions on chromosomes 1 or 13 were enriched for AP2-EREBP, AS2, C2C2-CO, HMG, and MYB transcription factors, and QTL on chromosomes 9 or 13 were enriched for the ALFIN-LIKE transcription factor and regulation of autophagy pathways. QTL modeling for individual root traits identified eight models explaining 13.2 to 31.8% of the phenotypic variation. 'Seyval blanc' was the grandparent contributing to the allele models that included a greater surface area, total root length, and branching (number of forks and links) traits promoting a greater root density. In contrast, V. riparia 'Manitoba 37' contributed the allele for greater average branch length (link length) and diameter, promoting a less dense elongated root system with thicker roots. LATERAL ORGAN BOUNDARY DOMAIN (LBD or AS2/LOB) and the PROTODERMAL FACTOR (PFD2 and ANL2) were identified as important candidate genes in the enriched pathways underlying the hotspots for grapevine adventitious RSA. The combined QTL hotspot and trait modeling identified transcription factors, cell cycle and circadian rhythm genes with a known role in root cell and epidermal layer differentiation, lateral root development and cortex thickness. These genes are candidates for tailoring grapevine root system texture, density and length in breeding programs.

Commercial Bioinoculants Increase Root Length Colonization and Improve Petiole Nutrient Concentration of Field-grown Grapevines

Agricultural bioinoculants containing arbuscular mycorrhizal fungi represent a potential opportunity to reduce the dependence of grapevines (Vitis) on agrochemicals. This field study assessed the ability of four commercial bioinoculants to colonize grapevine roots and their effects on petiole nutrient concentration, berry composition, and root morphology of ‘Pinot noir’ (Vitis vinifera) grafted onto rootstock ‘Couderc 3309’ (Vitis riparia × Vitis rupestris) and ‘Riesling’ (V. vinifera) grafted onto ‘Couderc 3309’ and Selection Oppenheim four (Vitis berlandieri × V. riparia). Three bioinoculants increased root mycorrhizal colonization; however, regardless of the treatment, mycorrhizal fungal structures were enhanced. Grapevine petiole nutrient concentration was improved by bioinoculants. Root diameter, root length density, and specific root length increased with greater mycorrhizal root colonization. Using bioinoculants to reduce chemical fertilizers may be a good strategy to improve grapevine productivity and health in cool climates; however, the impact of mycorrhizal bioinoculants in the vineyard may differ among scion–rootstocks, edaphoclimatic conditions, and vineyard soil microbiomes.

From Plant Nursery to Field: Persistence of Mycorrhizal Symbiosis Balancing Effects on Growth-Defence Tradeoffs Mediated by Rootstock

The plant domestication process led to crops with strongly modified growth-defense tradeoff features, and crops that were much more pampered in terms of nutrition, irrigation and defense measures, showing less ability to trigger adaptation strategies with respect to their wild relatives. It is worth noting that plants are not alone, they share their environment with a myriad of microbes supporting them with many relevant functions. We have already demonstrated that an arbuscular mycorrhizal fungal (AMF) inoculum (formed by two AMF species, i.e., Rhizophagus irregularis and Funneliformis mosseae) is able to balance growth and defense responses in two grapevine rootstocks with opposite tradeoff features. In the present study, we evaluated the persistence of AMF-mediated balancing effects under field conditions, confirming the positive impact of the symbiosis in vineyards. In detail, some genes related to nitrogen (N) uptake and metabolism were specifically modulated by the presence of the symbionts, while others were not. Additionally, photosynthetic performances and stilbenes accumulation were influenced by the AMF presence. Overall, our results open new questions about the timing of AMF inoculation in grapevine to obtain a stable and functional symbiosis, suggesting that an early inoculation can facilitate the interaction between grapevine roots and these beneficial microorganisms.

Study on Effects of salt stress on the Suberin Lamella of grapevine roots

Grape is one of the oldest tree species in the world which have a relatively high tolerance to salt stress. The function of Suberin Lamella is to control the transport of water and ions, which has a positive effect on salt tolerance. However, whether the suberin lamella of grape root is related to its salt-tolerance has not been revealed. In this study, suberin lamella in roots of two grape varieties, "Crimson seedless" and "1103p", were stained by FY0888. Results showed that salt stress induced the appearance and thickening of suberin lamella of grape root cortex. The induction effect was very obvious in salt-toerant "Crimson seedless", while the effect was weak in "1103P", indicating that the suberin lamella of grape was indeed involved in the salt tolerance of grape.

Managing Arbuscular Mycorrhizal Fungi in Arid Columbia Basin Vineyards of the Pacific Northwest United States

<h3>Abstract</h3> <h3>Background and goals</h3> Arbuscular mycorrhizal fungi (AMF) are root symbionts that help grapevines acquire nutrients from soil. Growers in many regions, including the Columbia River basin of Oregon and Washington, lack information needed to best manage AMF. Such lacking information includes understanding whether natural AMF populations are sufficient to ensure healthy colonization in new plantings, and what factors influence AMF in established plantings. <h3>Methods and key findings</h3> AMF colonization of grapevine fine roots was determined in 32 commercial vineyards and in a vineyard that was heavily infested by the northern root-knot nematode (NRKN, <i>Meloidogyne hapla</i>). Root colonization by AMF was as extensive in young vines (one- to two-years-old) as in older vines (&gt;15-years-old) examined in the survey, and was high throughout the season in the single vineyard trial. AMF colonization was greater overall in red wine grape cultivars than in white wine grape cultivars. AMF colonization correlated negatively with soil nitrate and leaf nitrogen (N) concentrations across vineyards, while arbuscules in roots correlated negatively with NRKN populations in soil. Both AMF and arbuscules in roots correlated negatively with NRKN populations per unit of fine root length at the beginning and end of the growing season in the heavily infested vineyard. <h3>Conclusions and significance</h3> Results suggest that AMF populations in soils of the Columbia River basin are ample to ensure high levels of grapevine root colonization, so inoculation is likely not needed when planting or replanting vineyards in the region. AMF colonization was reduced by high N and high populations of NRKN in soil.

Three Methods Assessing the Association of the Endophytic Entomopathogenic Fungus Metarhizium robertsii with Non-Grafted Grapevine Vitis vinifera.

Characterizing the association of endophytic insect pathogenic fungi (EIPF) with plants is an important step in order to understand their ecology before using them in biological control programs. Since several methods are available, it is challenging to identify the most appropriate for such investigations. Here, we used two strains of Metarhizium robertsii: EF3.5(2) native to the French vineyard environment and ARSEF-2575-GFP a laboratory strain expressing a green fluorescent protein, to compare their potential of association with non-grafted grapevine Vitis vinifera. Three methods were used to evaluate the kinetics of rhizosphere and grapevine endospheric colonization: (i) Droplet Digital (ddPCR), a sensitive molecular method of M. robertsii DNA quantification in different plant parts, (ii) culture-based method to detect the live fungal propagules from plant tissues that grew on the medium, (iii) confocal imaging to observe roots segments. Both strains showed evidence of establishment in the rhizosphere of grapevines according to the culture-based and ddPCR methods, with a significantly higher establishment of strain EF3.5(2) (40% positive plants and quantified median of exp(4.61) c/μL) compared to strain ARSEF-2575-GFP (13% positive plants and quantified median of exp(2.25) c/μL) at 96-98 days post-inoculation. A low incidence of association of both strains in the grapevine root endosphere was found with no significant differences between strains and evaluation methods (15% positive plants inoculated with strain EF3.5(2) and 5% with strain ARSEF-2575-GFP according to culture-based method). ddPCR should be used more extensively to investigate the association between plants and EIPF but always accompanied with at least one method such as culture-based method or confocal microscopy.

Biocontrol of Grapevine Crown Gall Performed Using Allorhizobium vitis Strain ARK-1

Grapevine crown gall (GCG), which is caused by tumorigenic Allorhizobium vitis (=Rhizobium vitis), is the most important bacterial disease in grapevine, and its economic impact on grapevine is very high. When young vines develop GCG, they often die, whereas older vines may show stress and poor growth depending on the severity of GCG, because GCG interferes with the vascular system of the grapevine trunk and prevents nutrient flow, leading to inferior growth and death. Viticultural practices and chemical control designed to inhibit GCG are only partially effective presently; thus, a biocontrol procedure could be a desirable and effective approach for GCG prevention. This article reviews the practical use of biocontrol options for GCG inhibition that involve using nonpathogenic and antagonistic A. vitis strains. In these studies, screening tests of biocontrol agents discovered nonpathogenic A. vitis strains VAR03-1, ARK-1, ARK-2, and ARK-3. After dipping grapevine roots in a suspension of candidate strains prior to planting in the field, treatment using ARK-1 was shown to significantly reduce the number of plants with GCG. A meta-analysis indicated that ARK-1 is very useful for controlling crown gall in various plant species, including grapevine. It was reported that when a mixture of ARK-1 and a tumorigenic strain was examined in grapevines, the expression levels of several virulence genes of the virulent strain were significantly lower. ARK-1 can reduce the pathogen population in grapevines and gall incidence. Moreover, ARK-1 can prime the induction of certain defense genes of grapevine. These results indicate that ARK-1 has a unique biocontrol mechanism and that it is a promising new biocontrol agent to control GCG.

Abscisic acid metabolism pathways differ between grapevine species, leaves, and roots during water deficit

Abscisic acid (ABA) metabolism is complex involving biosynthesis, conjugation, and catabolism. Differences in ABA metabolism (ABA, ABA-related metabolites, and transcripts) in response to water deficit (WD) were detected in leaves and roots of four Vitis species differing in drought tolerance: Vitis vinifera (Cabernet Sauvignon), Vitis champinii (Ramsey), Vitis riparia (Riparia Gloire), and Vitis vinifera x girdiana (SC2). Concentrations of ABA and ABA-related metabolites increased after moderate or severe WD depending on species, organ, and time. Differences in ABA, glycosylated-ABA, and ABA catabolite concentrations, as well as previously investigated related transcript abundances, revealed differences in ABA metabolism pathways among the species and organs. NCED3 was a key gene in the WD response of leaves and roots of all species. NCED3 transcript abundance and ABA concentration in drought-tolerant Ramsey increased earlier and to a greater extent than other species. These species provide informative genetic resources to study ABA metabolism and drought tolerance further.

Transcriptome analysis revealed the expression levels of genes related to abscisic acid and auxin biosynthesis in grapevine (Vitis vinifera L.) under root restriction.

The root system is essential for the stable growth of plants. Roots help anchor plants in the soil and play a crucial role in water uptake, mineral nutrient absorption and endogenous phytohormone formation. Root-restriction (RR) cultivation, a powerful technique, confines plant roots to a specific soil space. In the present study, roots of one-year-old “Muscat Hamburg” grapevine under RR and control (nR) treatments harvested at 70 and 125 days after planting were used for transcriptome sequencing, and in total, 2031 (nR7 vs. nR12), 1445 (RR7 vs. RR12), 1532 (nR7 vs. RR7), and 2799 (nR12 vs. RR12) differentially expressed genes (DEGs) were identified. Gene Ontology (GO) enrichment analysis demonstrated that there were several genes involved in the response to different phytohormones, including abscisic acid (ABA), auxin (IAA), ethylene (ETH), gibberellins (GAs), and cytokinins (CTKs). Among them, multiple genes, such as PIN2 and ERF113, are involved in regulating vital plant movements by various phytohormone pathways. Moreover, following RR cultivation, DEGs were enriched in the biological processes of plant-type secondary cell wall biosynthesis, the defense response, programmed cell death involved in cell development, and the oxalate metabolic process. Furthermore, through a combined analysis of the transcriptome and previously published microRNA (miRNA) sequencing results, we found that multiple differentially expressed miRNAs (DEMs) and DEG combinations in different comparison groups exhibited opposite trends, indicating that the expression levels of miRNAs and their target genes were negatively correlated. Furthermore, RR treatment indeed significantly increased the ABA content at 125 days after planting and significantly decreased the IAA content at 70 days after planting. Under RR cultivation, most ABA biosynthesis-related genes were upregulated, while most IAA biosynthesis-related genes were downregulated. These findings lay a solid foundation for further establishing the network through which miRNAs regulate grapevine root development through target genes and for further exploring the molecular mechanism through which endogenous ABA and IAA regulate root architecture development in grapevine.

Autotoxin affects the rhizosphere microbial community structure by influencing the secretory characteristics of grapevine roots.

Autotoxins secreted by roots into the soil can trigger rhizosphere microecological imbalances and affect root secretory properties resulting in conditions such as replanting disease. However, information on the effect of autotoxins on root secretion characteristics and regulation of the composition of rhizosphere microorganisms by altered root exudates is limited. In this study, autotoxin ρ-hydroxybenzoic acid (4-HBA) was added to the soil of potted grapevine seedlings, CO2 pulse-labeling, and DNA stable isotope probing were used to track the rhizosphere microbiome that assimilates root exudates. Bacterial and fungal microbiomes that assimilated plant-derived carbon were identified by high-throughput sequencing. Results showed that 4-HBA treatment altered bacterial and fungal communities in 13C-labeled organisms, with a lower abundance of beneficial bacteria (e.g., Gemmatimonas, Streptomyces, and Bacillus) and a higher abundance of potential pathogen fungi (e.g., Fusarium, Neocosmospora, Gibberella, and Fusicolla) by changing the composition of root exudates. The exogenous addition of upregulated compound mixtures of root exudates reduced the abundance of beneficial bacterial Bacillus and increased the abundance of potential pathogen fungi Gibberella. These results suggest that 4-HBA can alter root secretion properties and altered root exudates may enrich certain potential pathogens and reduce certain beneficial bacteria, thereby unbalancing the structure of the rhizosphere microbial community.

A grapevine by-product extract enriched in oligomerised stilbenes to control downy mildews: focus on its modes of action towards &lt;i&gt;Plasmopara viticola&lt;/i&gt;

Natural extracts, and particularly plant by-product extracts, can represent an eco-friendly alternative to synthetic pesticides to control crop diseases. We produced an extract from a mix of grapevine trunk and roots that contain a high amount of complex stilbenes (grapevine phytoalexins), especially ε- and r-viniferins. This extract conferred protection to grapevines against Plasmopara viticola (the causal agent of downy mildew) by displaying antimicrobial activities towards zoospore mobility and sporulation and by stimulating plant defences. From the perspective of its application in the field, a formulated preparation of the extract was proposed using polysorbate and sophorolipids. The formulated extract reduced the development of various oomycetes impacting grapevine, potato, tomato and melon in semi-controlled conditions. Thus, such grapevine extract constitutes a promising strategy to protect major cultivated plants against downy mildews.

Soil, vine, climate change; the challenge of predicting soil carbon changes and greenhouse gas emissions in vineyards and is the 4 per 1000 goal realistic?

The evaluation of the current and future impact of climate change on viticulture requires an integrated view on a complex interacting system within the soil-plant-atmospheric continuum under continuous change. Aside of the globally observed increase in temperature in almost all viticulture regions for at least four decades, we observe several clear trends at the regional level in the ratio of precipitation to potential evapotranspiration. Additionally the recently published 6th assessment report of the IPCC (The physical science basis) shows case-dependent further expected shifts in climate patterns which will have substantial impacts on the way we will conduct viticulture in the decades to come.Looking beyond climate developments, we observe rising temperatures in the upper soil layers which will have an impact on the distribution of microbial populations, the decay rate of organic matter or the storage capacity for soil organic carbon (SOC). All this influences the emission of greenhouse gases (GHGs) and the viscosity of water in the soil-plant pathway, altering the transport of water. Interactions between micro-organisms in the rhizosphere, the grapevine root system, degradation and fixation processes of SOC are complex and poorly understood but respond to environmental factors (such as increased soil temperatures), the plant material (rootstock for instance), and the cultivation system (for example bio-organic versus conventional, cover crop use versus open tillage). Increasing SOC stocks is discussed as a measure to reduce soil GHG emissions with the potential to improve the balance between GHG emissions and carbon removal from the atmosphere. Yet it is difficult to deduct the impact of climatic changes and cultivation practices on patterns of carbon storage or losses from soils. This paper presents a first attempt to quantify these potential impacts on SOC for a vineyard location using the RothC-model (Coleman and Jenkinson, 2005) in combination with the Geisenheim long-term (&gt; 100-year) soil temperature record and climate predictions by the STAR II-model of the Potsdam Institute of Climate Impact using a medium realization run (Orlowsky et al., 2008).It is shown that retaining pruning wood and using a full cover crop yielded a SOC increase of 16.2 t C ha-1 over time. However, CO2 emissions over the simulated time span were only slightly less than C-storage in the soil. It is concluded that cover crops in vineyards helps to achieve CO2-neutrality but additional measures are required to make vineyards a significant C-sink.

Chemical speciation of copper and manganese in solution of a copper-contaminated soil and young grapevine growth with amendment application

Copper (Cu)-based fungicide application to control foliar diseases in grapevine (Vitis vinifera L.) can increase soil Cu availability. Brazilian soils have high natural Cu and manganese (Mn) concentrations, increasing the potential for toxicity to grapevine plants. Application of amendment substances can reduce the concentrations of toxic chemical species of Cu and Mn in soil solution, especially for the soils grown with young plants. We evaluated the chemical speciation of Cu and Mn in soil solution and young grapevine growth using a contaminated soil with amendment application. Grapevine seedlings of Paulsen 1103 rootstock were grown for 12 months on an old vineyard (> 30 years of cultivation) soil without (control) and with vermicompost or limestone application. Grapevine dry matter, root morphological characteristics, and plant tissue Cu and Mn concentrations were evaluated. The cation and anion concentrations, dissolved organic carbon, pH, and chemical speciation of Cu and Mn in soil solution from different soil layers were analyzed. Vermicompost application did not reduce Cu and Mn phytotoxicity, and grapevine plants died after winter pruning. High soluble Mn concentration in soil (5.56 mg L–1 in 0–45 cm soil layer) and Mn concentration in plant tissue at pruning (380.8 mg kg–1) might be the primary cause of plant death. Limestone application reduced Cu2+ and Mn2+ chemical species in soil solution, thereby increasing plant growth. The Cu2+ and Mn2+ species were negatively correlated (P < 0.05) with grapevine shoot production at pruning (r = –0.92 and –0.97, respectively) and at the end of the trial (r = –0.73 and –0.51, respectively). Limestone application increased grapevine shoot and root dry matter production by 36% and 41%, respectively, while also presenting the highest root length and volume in the 5–10 cm soil layer. Limestone application is a viable and profitable alternative for reducing soil Cu and Mn availability and their phytotoxic effects.

New clearing protocol for tannic roots optical imaging.

The understanding of plant physiological complexity requires 3D imaging of the entire organ with subcellular resolution. However, most plant organs are highly opaque to light and their study under optical sectioning microscopes is difficult. By gathering the latest developments in the field of optical clearing of pigmented plant tissues, it was found that the clearing tannic roots (CTR) protocol drastically reduces light absorption by a depigmentation step and light scattering by the homogenisation of refractive indices through entire grapevine roots.

Root-Specific Expression of Vitis vinifera VviNPF2.2 Modulates Shoot Anion Concentration in Transgenic Arabidopsis.

Grapevines (Vitis vinifera L., Vvi) on their roots are generally sensitive to salt-forming ions, particularly chloride (Cl–) when grown in saline environments. Grafting V. vinifera scions to Cl–-excluding hybrid rootstocks reduces the impact of salinity. Molecular components underlying Cl–-exclusion in Vitis species remain largely unknown, however, various anion channels and transporters represent good candidates for controlling this trait. Here, two nitrate/peptide transporter family (NPF) members VviNPF2.1 and VviNPF2.2 were isolated. Both highly homologous proteins localized to the plasma membrane of Arabidopsis (Arabidopsis thaliana) protoplasts. Both were expressed primarily in grapevine roots and leaves and were more abundant in a Cl–-excluding rootstock compared to a Cl–-includer. Quantitative PCR of grapevine roots revealed that VviNPF2.1 and 2.2 expression was downregulated by high [NO3–] resupply post-starvation, but not affected by 25 mM Cl–. VviNPF2.2 was functionally characterized using an Arabidopsis enhancer trap line as a heterologous host which enabled cell-type-specific expression. Constitutive expression of VviNPF2.2 exclusively in the root epidermis and cortex reduced shoot [Cl–] after a 75 mM NaCl treatment. Higher expression levels of VviNPF2.2 correlated with reduced Arabidopsis xylem sap [NO3–] when not salt stressed. We propose that when expressed in the root epidermis and cortex, VviNPF2.2 could function in passive anion efflux from root cells, which reduces the symplasmic Cl– available for root-to-shoot translocation. VviNPF2.2, through its role in the root epidermis and cortex, could, therefore, be beneficial to plants under salt stress by reducing net shoot Cl– accumulation.