Grapevine Roots Research Articles

Stilbene production as part of drought adaptation mechanisms in cultivated grapevine (Vitis vinifera L.) roots modulates antioxidant status.

Stilbenes, naturally occurring polyphenolic secondary metabolites, play a pivotal role in adaptation of various plant species to biotic and abiotic factors. Recently, increased attention has been directed toward their potential to enhance plant stress tolerance. We evaluated drought tolerance of three grapevine varieties grown with different levels of water deficit. Throughout, we studied physiological mechanisms associated with drought stress tolerance, particularly stilbene accumulation in root tissues, using HPLC. Additionally, we explored the possible relationship between antioxidant potential and stilbene accumulation in response to water deficit. The results underscore the detrimental impact of water deficit on grapevine growth, water status, and membrane stability index, while revealing varying tolerance among the studied genotypes. Notably, Syrah variety had superior drought tolerance, compared to Razegui and Muscat d'Italie grapes. Under severe water deficit, Syrah exhibited a substantial increase in levels of stilbenic compounds, such as t-resveratrol, t-piceatannol, t-ɛ-viniferin, and t-piceid, in root tissues compared to other genotypes. This increase was positively correlated with total antioxidant activity (TAA), emphasizing the active role of resveratrol and its derivatives in total antioxidant potential. This demonstratres the potential involvement of resveratrol and its derivatives in enhancing antioxidant status of the drought-tolerant Syrah grape variety. Our findings suggest that these stilbenes may function as valuable markers in grapevine breeding programs, offering novel insights for the sustainable cultivation of grapevines in water-limited environments.

Superabsorbent hydrogels: A new tool for vineyard water management?

New superabsorbent hydrogels (SH) could be groundbreaking technologies for the adaptation of agriculture to climate change, but knowledge about their physio-chemical traits, their effects on soil hydrology, and their efficacy on tree crop physiology is very limited. In this work, two potassium polyacrylate SH (SH1 and SH2) and an organic material derived SH (SH3) were tested for their water holding capacity and the capability to improve soil hydrology according to the water demands of cultivated grapevine, one of the most relevant rainfed tree crops. All SH absorbed a significant amount of water as compared to their relative weight (from 9.19 g H2O/g polymer of SH3, to 369.64 g H2O/g polymer of SH2) and made it available at water potential (Ψ) levels compatible with grapevine root system uptake. When incorporated to the soil, all SH successfully increased soil field capacity, affecting also wilting point, and increasing maximum plant available water (from +43 % of SH2 to +84 % of SH1). All SH increased stem Ψ of potted vines subjected to a progressive water deficit, as compared to controls (+0.25 MPa at four days from irrigation suspension, +0.2 MPa at eight days from water suspension, when Control vines showed a stem Ψ of −1.63 MPa).Our work demonstrated for the first time the potentialities of three different SH and their positive effects on soil water relations. Both synthetic and organic-derived SH could improve vine water status under limited water supply. While other studies are needed to clarify effects according to different rootstocks and soils, the results pave the way for the integration of SH in vineyard water management.

Artificial Intelligence Techniques in Grapevine Research: A Comparative Study with an Extensive Review of Datasets, Diseases, and Techniques Evaluation.

In the last few years, the agricultural field has undergone a digital transformation, incorporating artificial intelligence systems to make good employment of the growing volume of data from various sources and derive value from it. Within artificial intelligence, Machine Learning is a powerful tool for confronting the numerous challenges of developing knowledge-based farming systems. This study aims to comprehensively review the current scientific literature from 2017 to 2023, emphasizing Machine Learning in agriculture, especially viticulture, to detect and predict grape infections. Most of these studies (88%) were conducted within the last five years. A variety of Machine Learning algorithms were used, with those belonging to the Neural Networks (especially Convolutional Neural Networks) standing out as having the best results most of the time. Out of the list of diseases, the ones most researched were Grapevine Yellow, Flavescence Dorée, Esca, Downy mildew, Leafroll, Pierce's, and Root Rot. Also, some other fields were studied, namely Water Management, plant deficiencies, and classification. Because of the difficulty of the topic, we collected all datasets that were available about grapevines, and we described each dataset with the type of data (e.g., statistical, images, type of images), along with the number of images where they were mentioned. This work provides a unique source of information for a general audience comprising AI researchers, agricultural scientists, wine grape growers, and policymakers. Among others, its outcomes could be effective in curbing diseases in viticulture, which in turn will drive sustainable gains and boost success. Additionally, it could help build resilience in related farming industries such as winemaking.

VvbHLH036, a basic helix-loop-helix transcription factor regulates the cold tolerance of grapevine.

Cold stress is an adverse environmental factor that limits the growth and productivity of horticulture crops such as grapes (Vitis vinifera). In this study, we identified a grapevine cold-induced basic helix-loop-helix (bHLH) transcription factor (VvbHLH036). Overexpression and CRISPR/Cas9-mediated knockout (KO) of VvbHLH036 enhanced and decreased cold tolerance in grapevine roots, respectively. Transcriptome analysis of VvbHLH036-overexpressed roots identified threonine synthase (VvThrC1) as a potential downstream target of VvbHLH036. We confirmed that VvbHLH036 could bind the VvThrC1 promoter and activate its expression. Both the transcripts of VvThrC1 and the content of threonine were significantly induced in the leaves and roots of grapevine under cold treatment compared to controls. Conversely, these dynamics were significantly suppressed in the roots of CRISPR/Cas9-induced knockout of VvbHLH036. These observations support the regulation of threonine accumulation by VvbHLH036 through VvThrC1 during cold stress in grapevine. Furthermore, overexpression and CRISPR/Cas9-mediated knockout of VvThrC1 also confirmed its role in regulating threonine content and cold tolerance in transgenic roots at low temperature. Exogenous threonine treatment increased cold tolerance and reduced the accumulation of superoxide anions and hydrogen peroxide in grapevine leaves. Together, these findings point to the pivotal role of VvbHLH036 and VvThrC1 in the cold stress response in grapes by regulating threonine biosynthesis.

Soil Traits and Grapevine Rootstock Genotypes Modulate Arbuscular Mycorrhizal Rate and Species in a Mediterranean Environment

The soil microbiota is a key component of agroecosystems, and understanding its traits is crucial for effective agronomic management. Among beneficial microorganisms, arbuscular mycorrhizal fungi (AMFs) are mutually associated with grapevine (Vitis vinifera L.), enhancing the ability of this cropping system to adapt to soil conditions and bolstering its resistance and resilience against abiotic stresses, particularly drought, by promoting root growth and enhancing the roots’ absorption surface. The objective of this on-field study was to determine AMF species richness and diversity along with their relation to soil chemical, physical, and biological characteristics in two adjacent organic vineyards in Central Italy. The two tested vineyards of the autochthonous cv. Aleatico differed by the presence of grafted (Vitis berlandieri × V. riparia rootstock; AL-420) or own-rooted (ungrafted V. vinifera L.; AL-ORV) vines. To this aim, soil and root samples were collected and geo-referenced. Analysis of the AMF species colonizing roots of both AL-ORV and AL-420 revealed the presence of four species: Scutellospora alterata, Paraglomus laccatum, Acaulospora laevis, and A. baetica, with S. alterata being the most frequent. Mycorrhization parameters were higher in the roots of grafted plants compared to ungrafted ones. A high beta-glucosidase (BG):N-acetylglusosaminidase (NAG) ratio in two tested vineyards indicated that microbes utilized more cellulose than chitin and peptidoglycan as dominant C resources. A negative correlation between mycorrhization rate (MyCP) and BG was observed, likely because AMFs form mutualistic relationships with plants, depending on the host plant for carbon. Results revealed a positive correlation between the degree of mycorrhizal association and the species involved, with the presence of copper and nickel among metals. Negative correlations were found concerning soil clay content along with beta-glucosidase. In conclusion, the grapevine root system was characterized by a differential symbiotic relationship with AMF species, whose development is influenced by the root genotype, soil texture, and biochemistry. Specifically, the increased frequency of AMFs in relation to copper content strengthens the evidence of their role in maintaining a vine’s production capacity in the event of soil contamination by this element.

Agricultural Managements Influence the Diversity of Arbuscular Mycorrhizal Fungi in Vineyards from Chilean Mediterranean Climate Ecosystems

PurposeGrapevine (Vitis vinifera L.) is a relevant crop, which is associated to arbuscular mycorrhizal fungi (AMF) that are influenced by agricultural practices. The hypothesis of this study is that organic/biodynamic management stimulates grapevine mycorrhizal colonisation and increases AMF diversity in Chilean vineyards. The aim of this study was to determine the influence of agricultural management on AMF association and AMF diversity in Chilean vineyards.MethodsMycorrhizal colonisation of grapevine roots from organic/biodynamic and conventional vineyards in Northern (Elqui Valley), Central (Casablanca and Cachapoal Valleys), and Southern Chile (Maule and Itata Valleys), was determined under a microscope. AMF diversity was analysed by morphological, and molecular characterisation of spores through SSU-ITS-LSU rRNA region sequence analyses.ResultsAMF colonisation of grapevine roots was influenced by vineyard management independent of the season. Higher mycorrhizal colonisation was detected in organic/biodynamic grapevine soils (20 − 35%), compared with conventional soils (6 − 31%). Twelve AMF species were identified in vineyards, belonging to five Glomeromycota families. Interestingly, organic/biodynamic vineyards showed higher AMF diversity. The three predominant morphotypes were Funneliformis verruculosum (GL1), Septoglomus sp. (GL4) and Septoglomus constrictum (GL5). Molecular analyses of AMF spores highlighted the occurrence of Septoglomus, Acaulospora, Pacispora and Cetraspora genera in vineyards.ConclusionsIn this study, AMF diversity in Chilean vineyards is described for the first time. The diversity of AMF in vineyards in Chile was higher than the diversity reported in other wine-producing ecosystems. The understanding of agricultural practices on AMF activity and diversity may be crucial to improve the vineyard management.

Vineyard management systems influence arbuscular mycorrhizal fungi recruitment by grapevine rootstocks in New Zealand.

Arbuscular mycorrhizal fungi (AMF) can perform significant functions within sustainable agricultural ecosystems, including vineyards. Increased AMF diversity can be beneficial in promoting plant growth and increasing resilience to environmental changes. To effectively utilize AMF communities and their benefits in vineyard ecosystems, a better understanding of how management systems influence AMF community composition is needed. Moreover, it is unknown whether AMF communities in organically managed vineyards are distinct from those in conventionally managed vineyards. In this study, vineyards were surveyed across the Marlborough region, New Zealand to identify the AMF communities colonizing the roots of different rootstocks grafted with Sauvignon Blanc and Pinot Noir in both conventional and organic systems. The AMF communities were identified based on spores isolated from trap cultures established with the collected grapevine roots, and by next-generation sequencing technologies (Illumina MiSeq). The identified AMF species/genera belonged to Glomeraceae, Entrophosporaceae, and Diversisporaceae. The results revealed a significant difference in AMF community composition between rootstocks and in their interaction with management systems. These outcomes indicated that vineyard management systems influence AMF recruitment by rootstocks and some rootstocks may therefore be more suited to organic systems due to the AMF communities they support. This could provide an increased benefit to organic systems by supporting higher biodiversity.

Improving grape fruit quality through soil conditioner: Insights from RNA-seq analysis of Cabernet Sauvignon roots.

The application of fertilizers and soil quality are crucial for grape fruit quality. However, the molecular data linking different fertilizer (or soil conditioner [SC]) treatments with grape fruit quality is still lacking. In this study, we investigated three soil treatments, namely inorganic fertilizer (NPK, 343.5 kg/hm2 urea [N ≥ 46%]; 166.5 kg/hm2 P2O5 [P2O5 ≥ 64%]; 318 kg/hm2 K2O [K2O ≥ 50%]), organic fertilizer (Org, 9 t/hm2 [organic matter content ≥ 35%, N + P2O5 + K2O ≥ 13%]), and SC (SC, 3 t/hm2 [humic acid ≥ 38.5%; C, 56.1%; H, 3.7%; N, 1.5%; O, 38%; S, 0.6%]), on 4-year-old Cabernet Sauvignon grapevines. Compared with the NPK- and Org-treated groups, the SC significantly improved the levels of soluble solids, tannins, anthocyanins, and total phenols in the grape berries, which are important biochemical indicators that affect wine quality. Furthermore, we conducted RNA-seq analysis on the grapevine roots from each of the three treatments and used weighted gene co-expression network analysis to identify five hub genes that were associated with the biochemical indicators of the grape berries. Furthermore, we validated the expression levels of three hub genes (ERF, JP, and SF3B) and five selected genes related to anthocyanin biosynthesis (UFGT1, UFGT2, UFGT3, GST, and AT) by using quantitative reverse transcription-polymerase chain reaction. Compared to the NPK and Org treatment groups, the SC treatment resulted in a significant increase in the transcription levels of three hub genes as well as VvUFGT1, VvUFGT3, VvGST, and VvAT. These results suggest that the SC can improve grape fruit quality by altering gene transcription patterns in grapevine roots and further influence the biochemical indices of grape fruits, particularly anthocyanin content. This study reveals that the application of SC can serve as an important measure for enhancing vineyard SC and elevating grape quality.

Root Distribution and Water Uptake Applied by Hydrogen and Oxygen Stable Isotopes for Lianas in Northwest China

The root distribution and water uptake of irrigated vines (Vitis vinifera L.) in arid oasis areas remain poorly understood, particularly in terms of the variations in water uptake resulting from plant type and growing period. In this study, excavation and soil coring were employed to investigate the root distribution of vines. Meanwhile, the water uptake dynamics of irrigated vines in an arid oasis area were developed using stable isotopes of hydrogen and oxygen in water bodies (δD and δ18O) and in crops and soil water, coupled with a direct inference approach and a linear mixed model (IsoSource). The soil layers were divided into nine layers via hierarchical cluster analysis. The results indicated that the vertical distributions of the total and fine roots of grapevines were mainly in the range of 40–160 cm, accounting for 93.1% (91.2%) and 92.5% (90.0%) of the total root (200 cm) distribution during May and October, respectively. In the horizontal direction, both the total root and fine root systems were mainly distributed within 0–100 cm from the trunk and contributed 81.2% and 79.8% of the total root distribution, respectively. Meanwhile, both the total root weight (length) density and fine root weight (length) density decreased gradually with increasing radial distance from the trunk in the 0–80 cm range. The main water uptake of vines was at 0–40 cm in June, 20–80 cm in July, and 40–100 cm in August. These findings suggest that the main depth of root water uptake increases during the whole growth stage for grapevines in arid oasis ecosystems. This information will help growers to improve irrigation efficiency and provide a data analysis of water conservation in an arid oasis area during water stress.

Effect of rootstock diversity and grafted varieties on the structure and composition of the grapevine root mycobiome

Effect of rootstock diversity and grafted varieties on the structure and composition of the grapevine root mycobiome

Effects of Long-Term High Temperatures in the Root Zone on the Physiological Characteristics of Grapevine Leaves and Roots: Implications for Viticulture Practices

Ridging cultivation and root restriction cultivation are beneficial due to their improvement of the soil permeability in the root zone of grapevine, and they are widely used in southern China, Japan, and other countries. However, with the intensification of global warming, when using ridging or root restriction cultivation, the soil temperature in the root zone can often reach 30 °C or even more than 35 °C during the summer, which is not conducive to the growth of grapevines. The aim of this study was to explore the effects of high root zone temperatures on the photosynthetic fluorescence characteristics of grapevine leaves, root respiration, and degree of lignification of roots and shoots, as well as to provide a theoretical foundation for the management of grapevine production and cultivation. One-year-old potted ‘Kyoho’ was used as the study material. Three root temperature treatments were implemented for 15 days (9:00–16:00): 25 °C (CK), 30 °C (T1), and 35 °C (T2). The results showed that the malondialdehyde and H2O2 levels in leaves increased, while the chlorophyll content decreased. The oxygen-evolving complex was inactivated, and PSII donor and acceptor sides were blocked, thus reducing the photosynthetic gas exchange capacity at high root zone temperatures. The grapevine root activity and root/shoot ratio decreased. Simultaneously, the lignin content in the roots and shoots increased. In addition, there was a significant increase in the expression of key genes (PAL, C4H, 4CL, F5H, COMT, CCR, and CAD) in the root lignin synthesis pathway. Heightened root zone temperatures increased cyanide-resistant respiration in roots and heat release in the PPP pathway to alleviate stress damage. Therefore, it is recommended to use grass, mulching, and other cultivation management methods to maintain root zone temperatures below 30 °C in order to ensure the normal growth of grapevines and promote a high and stable yield.

In Situ Sucrose Injection for Alteration of Carbohydrate Reserve Dynamics in Grapevine

Inconsistent yield of subtropical table grape across seasons is often associated with low carbohydrate reserves during flowering. In an attempt to increase TNC and thus yield, sucrose was injected into treated trunks during periods of high carbohydrate demand (i.e., between budburst and flowering). Total non-structural carbohydrate (TNC) concentration dynamics were assessed in the grapevine root and trunk tissues of both control and treated vines. In the control (untreated) vines, the TNC concentration in root and trunk tissues was 13.5% and 7.5% w/dw at leaf fall and 7.2% and 3.7% w/dw at flowering, respectively. This decrease in carbohydrate reserve was estimated at ~500 g/vine and is associated with the re-establishment of the plant canopy in early spring. Carbohydrate reserves remained stable or rose slightly between flowering and harvest and recovered between crop harvest and leaf fall. In treated vines, a constantly pressurised low-pressure in situ trunk injection system (69 kPa) with 5% w/v sucrose solution over 45 days from budburst (to flowering), in each of the two seasons, delivered a widely variable amount of sucrose into each vine with variation ascribed to the amount of internal dead wood in the trunk. In the best circumstances, an average of 150 g sucrose/vine/season was injected, and sucrose-injected vines had higher trunk TNC reserve (4.1% compared to 3.6% w/dw in the control) at flowering. A δ13C (‰) analysis confirmed the presence of injected sucrose in the shoot at flowering. However, the correlation between the amount of loaded sucrose and δ13C in young shoot tissue was poor, indicative of variable partitioning patterns. Inflorescence number per vine and berry yield were markedly higher in sucrose-injected vines, but differences were not significant given the high variation between vines. The addition of KCl to the sucrose solution and use of the healthy vines are recommended to increase sucrose loading using the injection method to address inconsistent yielding of subtropical table grape.

Sustainable In Silico-Supported Ultrasonic-Assisted Extraction of Oligomeric Stilbenoids from Grapevine Roots Using Natural Deep Eutectic Solvents (NADES) and Stability Study of Potential Ready-to-Use Extracts.

Grapevine roots, as a side-stream of a vineyard, are a sustainable resource for the recovery of oligomeric stilbenoids, such as the bioactive r-viniferin. The aim of this study is to evaluate an in silico-supported method, based on the Conductor-like Screening Model for Real Solvents (COSMO-RS), for selection of environmentally friendly natural deep eutectic solvents (NADES) with regard to the extraction of grapevine roots. The most suitable NADES system for ultrasonic-assisted extraction of r-viniferin was choline chloride/1,2-propanediol. The optimal extraction parameters for r-viniferin were determined using single-factor experiments as follows: choline chloride/1,2-propanediol 1/2 mol/mol, 10 wt% H2O, biomass/NADES ratio 1/10 g/g, and 10 min extraction time. Under optimized conditions, the extraction yield of r-viniferin from grapevine roots reached 76% of the total r-viniferin content. Regarding stability, stilbenoids in choline chloride/1,2-propanediol remained stable during 128 days of storage at ambient temperature. However, fructose/lactic acid-based NADES were observed to degrade stilbenoids; therefore, the removal of the NADES will be of interest, with a suitable method implemented using Amberlite® XAD-16N resin. As green solvents, the NADES have been used as effective and environmentally friendly extractants of stilbenoid-containing extracts from grapevine roots for potential applications in the cosmetic and pharmaceutical industry or as nutraceuticals in the food industry.

Temperature response and thermal performance analysis of a hybrid gravity heat pipe(HGHP) for winter soil warming of grapevine roots:a field experiment

ravity heat pipe is a highly efficient heat transfer device that shows great potential for efficient development of shallow geothermal energy.The adiabatic section of the gravity heat pipe does not exchange heat with the external environment during operation, and the use of low-cost PPR materials with low thermal conductivity to replace the expensive metal materials in the adiabatic section can significantly reduce the cost of gravity heat pipe materials.In this study, a new hybrid gravity heat pipe (HGHP) composed of metallic copper and PPR materials is designed, in which the evaporation section and condensation section, which exchange heat with the external environment, are made of metallic copper, and the adiabatic section, which does not exchange heat with the external environment, is made of PPR material, and the analysis of HGHPs and heat transfer characteristics of the similar principle has not yet been reported in the public literature.It was found that the average soil temperature around the condensation section of CGHP and HGHP during the experimental period increased by 4.94℃ and 3.08℃, respectively, compared to the soil temperature of the control group without heat pipe, which was a significant warming effect;Both sets of heat pipes exhibit good isothermal performance,and the CGHP isothermal performance is better than the HGHP;The thermal power of CGHP and HGHP is 55.11 and 42.61 W respectively, which is 22.68% lower than that of CGHP due to the increased thermal resistance of the connecting joints of HGHP.The cost analysis found that the cost of HGHP is 48.39% lower than that of CGHP, and the material cost decreases significantly. This study provides a feasible solution to reduce the cost of shallow geothermal energy development.

Enhancing biological activities and phenolic content of wild grapevine roots by severe drought stress

Wild grapevines are a rich source of polyphenolic compounds. Various environmental factors can influence these bioactive metabolites, contributing to stress mitigation and adaptation. The present study aimed to investigate the impact of prolonged drought stress on the accumulation of phytochemicals, antioxidants, and antimicrobial activity in the roots of the endangered Tunisian wild grapevine (Vitis vinifera subsp. sylvestris) "Tebaba" genotype. The results revealed that under prolonged drought stress, there was a significant increase in total phenolic compounds, total flavonoid content, and stilbenes, which showed a positive and significant correlation with the total antioxidant activity. Furthermore, the ethanolic extracts demonstrated an enhanced in vitro antibacterial effect against selected human pathogenic bacterial strains, including Staphylococcus aureus, Methicillin-resistant S. aureus, and Enterococcus faecalis. The minimum inhibitory concentration (MIC) and the minimal bactericidal concentration (MBC) values, relative to prolonged drought stress, ranged from 125 to 250 µg/mL. The values of the ratio between MBC and the MIC showed that the activity of the root extract was bactericidal in all cases (MBC/MIC ≤ 2). This study highlights the potential of wild grapevine roots enriched with drought-inducible phenolic compounds, as a promising source of antimicrobial agents relevant to human health applications.

Grapevine bacterial communities display compartment-specific dynamics over space and time within the Central Valley of California

BackgroundPlant organs (compartments) host distinct microbiota which shift in response to variation in both development and climate. Grapevines are woody perennial crops that are clonally propagated and cultivated across vast geographic areas, and as such, their microbial communities may also reflect site-specific influences. These site-specific influences along with microbial differences across sites compose ‘terroir’, the environmental influence on wine produced in a given region. Commercial grapevines are typically composed of a genetically distinct root (rootstock) grafted to a shoot system (scion) which adds an additional layer of complexity via genome-to-genome interactions.ResultsTo understand spatial and temporal patterns of bacterial diversity in grafted grapevines, we used 16S rRNA amplicon sequencing to quantify soil and compartment microbiota (berries, leaves, and roots) for grafted grapevines in commercial vineyards across three counties in the Central Valley of California over two successive growing seasons. Community composition revealed compartment-specific dynamics. Roots assembled site-specific bacterial communities that reflected rootstock genotype and environment influences, whereas bacterial communities of leaves and berries displayed associations with time.ConclusionsThese results provide further evidence of a microbial terroir within the grapevine root systems but also reveal that the microbiota of above-ground compartments are only weakly associated with the local soil microbiome in the Central Valley of California.

Comparative analysis of different bio-organic fertilizers on growth and rhizosphere environment of grapevine seedlings

Grapevine seedlings need to absorb a lot of nutrients from the soil during the growth process, and appropriate fertilizer can greatly promote the growth of seedlings. The purpose of this study was to investigate the effects of different bio-organic fertilizers (BOF) on shoot and root growth, soil biochemical characteristics, and bacterial communities of ‘Shine Muscat’ and ‘Kyoho’ seedlings. Four treatments were established: no fertilizer (CK), chemical fertilizer + organic fertilizer (T1), chemical fertilizer + bio-organic fertilizer 1 (T2, containing Bacillus amyloliquefaciens), chemical fertilizer + bio-organic fertilizer 2 (T3, containing Trichoderma). The results showed that BOF had better effects on growth and rhizosphere environment of grapevine seedling than organic fertilizer (OF) treated group. The shoot growth, chlorophyll content, and root growth with BOF of grapevine seedlings were generally better than those treated with OF. Compared with T1, T2 and T3 made grapevine seedlings meet the fixed drying requirement (main shoot 0.8 m) 1–4 weeks earlier. The expansion of roots and the improvement of root activity under BOF treatment were also beneficial to plant growth. Moreover, transcriptome analysis showed that BOF enhanced the phytohormones and cell wall processes in grapevine root, and up-regulated the expression of cell wall-related genes such as XTH23, EXPs, PME17, and auxin related genes such as ABCBs and GH3. In addition, BOF increased soil organic matter content, available nitrogen, available potassium, available phosphorus, and enzyme activity (soil catalase, urease, sucrase, and nitrate reductase). The Shannon and Chao values of T2 were higher than those of T1 and CK, which improved the diversity and richness of soil microbial community. As compared to CK, T2 treatment increased the symbiotic nitrogen fixing Proteobacteria by 4.10 %, and reduced Acidobacteria by 9.79 %. Actinobacteria, which is related to the degradation of stubborn polymers, was the dominant group in T2 treatment, accounting for 10.17 %. As compared to CK and T1, Actinobacteria was increased by 6.89 % and 5.66 %. In summary, BOF could promote the growth of grapevine seedlings by improving phenotypic traits, soil fertility, bacterial diversity, richness abundance, and provide theoretical and technical support for grapevine garden construction and tree management.

Arbuscular mycorrhizal fungal communities differ in neighboring vineyards of different ages.

Arbuscular mycorrhizal fungi (AMF) are key organisms in viticultural ecosystems as they provide many ecosystem services to soils and plants. Data about AMF community dynamics over time are relatively scarce and at short time scales. Many factors such as the soil, climate, and agricultural practices could modify the dynamics and functions of microbial communities. However, the effects on microbial communities of plant phenology and changes in plant physiology over time largely have been overlooked. We analyzed the diversity of AMF in three geographically close vineyards with similar soil parameters for 2years. The plots differed in grapevine age (11, 36, and110years), but had the same soil management practice (horse tillage). Diversity analyses revealed a difference in the composition of AMF communities between the soil and grapevine roots and among roots of grapevines of different ages. This underlines AMF adaptation to physiological changes in the host which can explain the development of different AMF communities. The dynamics of AMF communities can highlight their resilience to environmental changes and agricultural practices.

Arbuscular Mycorrhizal Fungi Induce Changes of Photosynthesis-Related Parameters in Virus Infected Grapevine.

The negative effects of viruses and the positive effects of arbuscular mycorrhizal fungi (AMF) on grapevine performance are well reported, in contrast to the knowledge about their interactive effects in perennial plants, e.g., in grapevine. To elucidate the physiological consequences of grapevine-AMF-virus interactions, two different AMF inoculum (Rhizophagus irregularis and 'Mix AMF') were used on grapevine infected with grapevine rupestris stem pitting virus, grapevine leafroll associated virus 3 and/or grapevine pinot gris virus. Net photosynthesis rate (AN), leaf transpiration (E), intercellular CO2 concentration (Ci) and conductance to H2O (gs) were measured at three time points during one growing season. Furthermore, quantum efficiency in light (ΦPSII) and electron transport rate (ETR) were surveyed in leaves of different maturity, old (basal), mature (middle) and young (apical) leaf. Lastly, pigment concentration and growth parameters were analysed. Virus induced changes in grapevine were minimal in this early infection stage. However, the AMF induced changes of grapevine facing biotic stress were most evident in higher net photosynthesis rate, conductance to H2O, chlorophyll a concentration, total carotenoid concentration and dry matter content. The AMF presence in the grapevine roots seem to prevail over virus infection, with Rhizophagus irregularis inducing greater photosynthesis changes in solitary form rather than mixture. This study shows that AMF can be beneficial for grapevine facing viral infection, in the context of functional physiology.

Deciphering Plant-Induced Responses toward Botrytis cinerea and Plasmopara viticola Attacks in Two Grapevine Cultivars Colonized by the Root Biocontrol Oomycete, Pythium oligandrum

Two major diseases that affect grapevine leaves and berries are controlled by the oomycete Pythium oligandrum. As the efficacy of biocontrol agents strongly depends on factors such as the trophic behaviors of pathogens and cultivar susceptibility, a two-disease approach was implemented to evaluate the activity of P. oligandrum against Botrytis cinerea (the necrotrophic fungus of gray mold) and Plasmopara viticola (the biotrophic oomycete of downy mildew) on two grapevine cultivars with different susceptibilities to these two pathogens. The results show that grapevine root inoculation with P. oligandrum significantly reduced P. viticola and B. cinerea infection on the leaves of the two cultivars, but with differences. This was observed when the relative expression of 10 genes was measured in response to each pathogen, and could be attributed to their lifestyles, i.e., biotrophic or necrotrophic, which are related to the activation of specific metabolic pathways of the plant. In response to P. viticola infection, genes from the jasmonate and ethylene pathways were mainly induced, whereas for B. cinerea, the genes induced were those of the ethylene-jasmonate pathway. The different levels of defense against B. cinerea and P. viticola could also explain the difference in cultivar susceptibility to these pathogens.