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A study on Sauvignon blanc (SB) cultivar in France showed that curettage had an effect on the resilience of GTD grapevines. No experiments, however, have been conducted on its effects on wine quality, particularly on white Sauvignon blanc cultivar wines. Methods and results: Grapevines from Sauvignon blanc cultivar that had expressed Esca-foliar symptoms were used for the study, with some of them having been curetted in 2014. Subsequently, bunches from Control (asymptomatic), Curetted and Esca-symptomatic vines were harvested in 2017 and 2018 in order to produce white wine. Technical and chemical results on both must and wine showed that wines from curetted plants were similar to those from asymptomatic vines. There were differences, however, for Esca-diseased vines, where the alcoholic fermentation of musts was faster than for the other modalities. Olfactometry results showed that, for the one-year-old 2017 vintage wines, no differences were detected, although they were for the 2018 vintage. Conclusion: The results of the chemical analyses and wine tasting showed that the wines from curetted and asymptomatic grapevines were similar, and that their quality was the same. Significance of the study: The quality of wines from curetted vines compared to asymptomatic ones was confirmed and validated through chemical and sensory analyses of the must and the one-year-old wines. k e y w o r d s curettage, Esca, Sauvignon blanc, musts, chemical analyses, wine quality

International audience; Methyl salicylate (MeSA) is a plant metabolite that induces plant defence resistance and an odorous volatile compound presenting green nuances. This volatile compound was shown to be present in wine samples, sometimes at concentrations above its olfactory detection threshold. MeSA is localized in grapes, particularly in the skins and stems, and is extracted during red wine vinification. It was detected at the highest concentrations in wines of several grape varieties, made from grapes affected by cryptogamic diseases, namely downy mildew caused by Plasmopara viticola, and black rot caused by Guignardia bidwellii. It has also been detected in wines from vines affected by Esca, a Grapevine Trunk Disease. MeSA can also be considered to be a chemical marker in grapes and wine indicative of the level of development of several vine cryptogamic diseases.

International audience; Esca, a major grapevine trunk disease in old grapevines, is associated with the colonization of woody tissues by a broad range of plant pathogenic fungi. To identify which fungal and bacterial species are involved in the onset of this disease, we analysed the microbiota from woody tissues of young (10-year-old) grapevines at an early stage of esca. Using meta-barcoding, 515 fungal and 403 bacterial operational taxonomic units (OTUs) were identified in woody tissues.In situhybridization showed that these fungi and bacteria co-inhabited in grapevine woody tissues. In non-necrotic woody tissues, fungal and bacterial microbiota varied according to organs and seasons but not diseased plant status.Phaeomoniella chlamydospora, involved in the Grapevine trunk disease, was the most abundant species in non-necrotic tissues from healthy plants, suggesting a possible non-pathogenic endophytic behaviour. Most diseased plants (70%) displayed cordons, with their central white-rot necrosis colonized essentially by two plant pathogenic fungi (Fomitiporia mediterranea: 60%-90% andP. chlamydospora: 5%-15%) and by a few bacterial taxa (Sphingomonasspp. andMycobacteriumspp.). The occurrence of a specific association of fungal and bacterial species in cordons from young grapevines expressing esca-foliar symptoms strongly suggests that that microbiota is involved in the onset of this complex disease.

International audience; Re-emergence of Grapevine Trunk Diseases (GTDs) in many world vineyards within the span of a mere two decades has become a subject of major concern for the viticulture sector. In Tunisia, knowledge about the symptoms of GTDs and the associated microflora is hitherto incomplete. In order to investigate this point, ten vineyards served as model for the analysis and monitoring of the symptoms of GTDs on cv. Italia (Muscat d’Italie) used to produce table grapes, in the Northern region of Tunisia. Depending on the vineyards, typical GTD-foliar symptoms with incidence ranging from 0.03% to 6% were observed. Fungal strains were isolated from necrotic wood tissues of the trunk of grapevines showing decline, small and distorted leaves and chloroses. Sequencing of the rDNA-Internal Transcribed Spacer region of the fungal strains allowed us to identify for the first time in Tunisia three fungi described in the literature as involved in GTDs: Lasidiodiplodia pseudotheobromae, Neofusicoccum parvum and Schizophyllum commune. The ability of these fungal strains to grow in Mediterranean climate was investigated by studying mycelial growth at various temperatures. As these fungal strains were isolated from the same wood samples, their ability to compete in vitro and in planta was tested, as well as their pathogenicity. For that purpose, strains were inoculated singly or in combination on cv. Italia young vines. Pathogenicity of the isolated fungi was evident but positive interaction between fungal strains was not observed.

International audience; Esca is a Grapevine Trunk Disease (GTD) caused by a broad range of taxonomically unrelated fungal pathogens. These attack grapevine wood tissues inducing necroses even in the conductive vascular tissues, thus affecting the vine physiology and potentially leading to plant death. However, the influence of Esca on leaf and whole-plant water transport disruption remains poorly understood. In this paper, a detailed analysis of xylem-related physiological parameters in grapevines that expressed Esca-foliar symptoms was carried out. The experiments were conducted in a vineyard in the Bordeaux region (France) on cv. Cabernet-Sauvignon (Vitis vinifera L.) grapevines, which were monitored for Esca-foliar symptoms over a two-year period. Heat dissipation sap-flow sensors were installed during the summer on grapevines having expressed or not Esca-foliar symptoms. Leaf water potential, stomatal conductance and leaf transpiration were also measured. Physiological monitoring showed that sap flow density and whole-plant transpiration of Esca-infected grapevines decreased significantly a week before the first foliar symptoms appeared. When atmospheric water demand (Vapour Pressure Deficit, VPD) was the highest, both parameters tended to be about twice as low in symptomatic grapevines as in asymptomatic ones. Sap flow density data at the maximum transpiration-time, was systematically 29-30% lower in Esca-infected grapevines compared to control plants before or after the appearance of Esca-foliar symptoms. This trend was observed whatever the temperatures and VPD values measured. In Esca-diseased plants, larger amounts of necrotic wood, mainly white rot, were found in the trunk and cordon of symptomatic grapevines compared to healthy ones, suggesting necroses have an influence in reducing the whole-plant hydraulic capacity. This study reveals that the use of physiological monitoring methods, together with the visual monitoring of foliar symptoms, could prove useful in providing accurate measurements of Esca disease severity.

International audience; Aspergillus spp. are fungal pathogens that attack the grape and that are known for their secretion of mycotoxins, in particular, ochratoxin which is very toxic. A total of 39 bacterial strains isolated from the rhizosphere in Tunisian vineyards were identified using 16S rDNA and rpob gene sequencing: 35 were Bacillus spp. strains, 2 were Brevibacterium spp., 1 was Paenibacillus sp. and 1 strain was Microbacterium oxydans. Biochemical and microbiological screenings revealed that those 39 strains (i) metabolized differently carbon sources, (ii) possessed antibiotic genes and (iii) produced siderophores. Based on their PGP traits, 21 strains were selected and tested in vitro for their antagonistic effect against two fungal pathogens, Aspergillus ochraceus and A. carbonarius. All the tested antagonists were able to reduce the growth of A. ochraceus, with Bacillus amyloliquefaciens being the most efficient; and A. carbonarius, in particular Bacillus pumilus. In vitro screening using detached berries showed the potential of B. pumilus strain G3AX for inhibiting contaminations by Aspergillus spp., that are OTA-producing fungi. At the berry surface, the efficacy of the bacterial strains strongly depended on the presence or absence of wounds.

Background and Aims The objective of this study was to analyse the various fungal communities that colonise functional wood tissues of old vines that did not express symptoms of grapevine trunk diseases (i.e. Esca and Eutypa dieback) in the year of sampling. Plants of the cultivar Baco Blanc a grapevine hybrid of Folle Blanche and Noah used to produce Armagnac in France were sampled. Methods and Results Forty-two and 58-year-old vines, planted in the same vineyard, were uprooted, cut longitudinally and their functional wood tissues sampled. Culture-dependent and single-strand conformational polymorphism methods were used to compare the fungal communities colonising these wood tissues. It was shown that the fungal communities were significantly different depending on the age of the grapevines. A total of 421 fungal strains were isolated and identified by internal transcribed spacer region sequencing. Conclusions Many grapevine trunk diseases fungal pathogens, particularly the causal agents of Esca (42-year-old vines) and Eutypa dieback (58-year-old vines), as well as numerous potentially plant-beneficial mycoparasites (e.g. Trichoderma spp.), were isolated from the functional wood tissues of old grapevines. Significance of the Study The lack of foliar symptoms among older grapevines may reflect an ‘equilibrium’ among trunk fungal pathogens, mycoparasites and saprobes in the functional wood tissues of trunks.

International audience; Botrytis cinerea and Neofusicoccum parvum are devastating fungal pathogens of grapevines. A total of 46 bacterial strains isolated from grapevines were screened for their antagonistic activity toward B. cinerea, which causes gray mold, and N. parvum, which causes cankers, trunk diseases and berry rot. In vivo screening using detached berries and leaf discs and in planta screening using growing grapevine cuttings were compared to select the most efficient biological control agents. On grapevine leaf discs, the most effective strain, Bacillus ginsengihumi, exhibited more than 80% antagonistic activity against the two major grapevine subpopulations of Botrytis cinerea (transposa and vacuma). At the berry surface, the efficacy of the bacterial strains strongly depended on the presence or absence of wounds. On stem cuttings, some strains, notably Pantoea agglomerans, were able to significantly reduce the length of the necrosis caused by N. parvum. Thus, both the plant parts and the pathogen species may significantly affect the efficacy of the bacterial strain. Marked differences between the two fungal pathogen species in terms of strain inhibitory efficacy were observed on wounded berries, as some Bacillus spp. strains efficiently controlled B. cinerea but not N. parvum. Noticeable differences in bacterial antagonist efficiencies were detected between berries and leaf discs inoculated with B. cinerea (transposa), e.g., some Paenibacillus spp. strains were efficient on leaves but not on berries. Synergistic relationships were also revealed between several bacterial strains and the pathogens. Some bacterial strains (e.g., Bacillus licheniformis) reduced B. cinerea rot severity in wounded and unwounded berries, but they increased N. parvum necrosis on stem cuttings.

The worldwide increase in grapevine trunk diseases, mainly esca, represents a major threat for vineyard sustainability. Biocontrol of a pioneer fungus of esca, Phaeomoniella chlamydospora, was investigated here by deciphering the tripartite interaction between this trunk-esca pathogen, grapevine and the biocontrol-oomycete, Pythium oligandrum. When P. oligandrum colonizes grapevine roots, it was observed that the wood necroses caused by P. chlamydospora were significantly reduced. Transcriptomic analyses of plant and fungus responses were performed to determine the molecular events occurring, with the aim to relate P.chlamydospora degradation of wood to gene expression modulation. Following P. oligandrum-root colonization, major transcriptomic changes occurred both, in the grapevine-defense system and in the P. chlamydospore-virulence factors. Grapevine-defense was enhanced in response to P. chlamydospora attacks, with P. oligandrum acting as a plant-systemic resistance inducer, promoting jasmonic/ethylene signaling pathways and grapevine priming. P. chlamydospora pathogenicity genes, such as those related to secondary metabolite biosynthesis, carbohydrate-active enzymes and transcription regulators, were also affected in their expression. Shifts in grapevine responses and key-fungal functions were associated with the reduction of P. chlamydospora wood necroses. This study provides evidence of wood fungal pathogen transcriptional changes induced by a root biocontrol agent, P. oligandrum, in which there is no contact between the two microorganisms.

International audience; In soilless culture, slow filtration is used to eliminate plant pathogenic microorganisms from nutrient solutions. The present study focused on the characterization and the potential functions of microbial communities colonizing the nutrient solutions recycled on slow filters during a whole cultivation season of 7 months in a tomato growing system. Bacterial microflora colonizing the solutions before and after they flew through the columns were studied. Two filters were amended with Pseudomonas putida (P-filter) or Bacillus cereus strains (B-filter), and a third filter was a control (C-filter). Biological activation of filter unit through bacterial amendment enhanced very significantly filter efficacy against plant potential pathogens Pythium spp. and Fusarium oxysporum. However, numerous bacteria (103–104 CFU/mL) were detected in the effluent solutions. The community-level physiological profiling indicated a temporal shift of bacterial microflora, and the metabolism of nutrient solutions originally oriented towards carbohydrates progressively shifted towards degradation of amino acids and carboxylic acids over the 7-month period of experiment. Single-strand conformation polymorphism fingerprinting profiles showed that a shift between bacterial communities colonizing influent and effluent solutions of slow filters occurred. In comparison with influent, 16S rDNA sequencing revealed that phylotype diversity was low in the effluent of P- and C-filters, but no reduction was observed in the effluent of the B-filter. Suppressive potential of solutions filtered on a natural filter (C-filter), where the proportion of Proteobacteria (α- and β-) increased, whereas the proportion of uncultured candidate phyla rose in P- and B-filters, is discussed.

Hot water treatment (HWT) is used in nurseries to control pathogenic fungi involved in Grapevine Trunk Diseases (GTDs), as well as other pathogens, such as phytoplasmas. The long-term impact of this treatment on the entire microflora, especially on the general fungal microbiota living inside plants, still remains however unknown. In this study, the fungal microflora of vineyard plants, treated or not by HWT 14 and 15 years earlier were compared at different plant part levels. The fungal microflora was relatively abundant in the different types of wood tissues. Certain fungal genera were first isolated and then identified on the basis of their treatment or not by HWT. A significant change between 2010 and 2011, the two sampling years, was detected. Although the HWT may have affected the cuttings microflora at the nursery stage, this had not persisted after several years of HWT treatment for the fungi, especially the pathogenic ones. As HWT does not have a significant long-term control effect on GTD pathogens in mature plants in the vineyards, applying other sanitary methods as soon as HWT-young vines are planted in the vineyards is recommended.

Vineyards throughout the world, including Tunisia, are being attacked by Grapevine Trunk Diseases (GTDs) such as Esca and Botryosphaeriae dieback. In this study, the bacterial microflora colonizing the non-necrotic and necrotic wood tissues of Tunisian mature grapevines (cv Muscat d’Italie) was investigated. Both types of tissues were studied in order to decipher microbial communities associated with them and to find a suitable BCA that can be applied to the Tunisian terroir. Single-Strand Conformation Polymorphism (SSCP) analyses showed that complex bacterial communities specifically colonized both types of wood tissues. The 19 most abundant cultivable strains, selected on their morphology, were isolated from plant samples and assigned to Pantoea , Pseudomonas , Curtobacterium and Bacillus species based on the 16S rRNA and rpo B genes. Biochemical and microbiological screenings revealed that those 19 strains (i) metabolized differently carbon sources, even within the same species, (ii) possessed antibiotic genes, (iii) produced siderophores and solubilized phosphates and (iv) had an in vitro antagonistic effect against 3 fungal pathogens ( Lasidiodiplodia pseudotheobromae , Neofusicoccum parvum and Schizophyllum commune ) involved in GTDs. One strain, Bacillus subtilis “B6”, had a positive effect on young vines of a cultivar, Muscat d’Italie, frequently planted in Tunisia, by reducing the size of the wood necrosis caused by N. parvum , showing its potential to counteract infection caused by this GTDs agent .

International audience; In the present study, 25 rhizobacterial isolates, obtained from rhizosphere of healthy tomato plants collected from various tomato-growing sites in Tunisia, were tested in vitro and in vivo against Rhizoctonia solani. This bacterial collection, composed of isolates belonging to Bacillus spp., Enterobacter cloacae, Chryseobacterium jejuense, and Klebsiella pneumoniae, was assessed for its antifungal potential against R. solani the causative agent of Rhizoctonia Root Rot disease in various crops including tomato. Antifungal activity of diffusible and volatile metabolites derived from these isolates was tested against target pathogen using dual and distance culture bioassays, respectively. Growth inhibition rates, recorded after 5 days of incubation at 25°C, depended significantly upon tested bacterial isolates and screening methods and reached 34-59% and 18-45% for diffusible and volatile metabolites, respectively. The screening of disease-suppressive and plant growth-promoting abilities of these tomato-associated rhizobacteria showed 47-100% decrease in disease severity and significant increments in plant height by 62-76%, roots fresh weight by 53-86%, and aerial parts fresh weight by 34-67% compared to pathogen-inoculated and untreated control. B. thuringiensis B2 (KU158884), B. subtilis B10 (KT921327) and E. cloacae B16 (KT921429) were found to be the most efficient isolates in decreasing R. solani radial growth, suppressing disease severity, and enhancing plant growth.

International audience; In the present study, a total of 200 rhizobacterial isolates were obtained from rhizosphere of healthy tomato plants grown in fields with a history of severe soilborne diseases and mainly crown and root rots. Screened their capacity to suppress in vitro growth of Sclerotinia sclerotiorum and Rhizoctonia solani, 69 and 57 isolates out of the 200 tested were shown able to inhibit significantly the mycelial growth of target pathogens by 11-62% relative to control. The 25 most effective isolates, leading to suppression of both fungi by more than 45% over control, were selected and subjected to morphological, biochemical, molecular, and metabolic characterizations. This collection of tomato-associated rhizobacteria exhibited a great morphological and biochemical diversity. Sequencing of 16S rRNA and rpoB genes led to the identification of four genera namely Bacillus, Chryseobacterium, Enterobacter, and Klebsiella. The most frequent species were B. amyloliquefaciens, B. thuringiensis, B. megaterium, B. subtilis, E. cloacae, C. jejuense, and K. pneumoniae. Screening for their plant growth-promoting properties, 20 isolates were shown able to produce siderophore, 18 had solubilized phosphate, and 19 were capable to synthesize indole-3- acetic acid (IAA). PCR amplification of lipopeptide biosynthetic genes revealed the presence of genes encoding fengycin A and bacillomycin D biosynthesis in 18 and 16 isolates, respectively. Metabolic characterization performed using Biolog™ Ecoplates indicated that tomato-associated rhizobacteria displayed a large metabolic activity and they were able to use a wide range of carbon sources with the increase of the incubation duration. Based on their metabolic profiles, these rhizobacterial isolates were grouped into eight major clusters generated at the different sampling times (24, 48 and 120 h of incubation). Average well-color development (AWCD) values were found to be positively correlated with the Shannon diversity index.

International audience; Germination of conidia of eight botryosphaeriaceous fungi infecting grapevines was evaluated after 2, 4, 6, 12, and 24 h incubation under eight different temperatures (5, 10, 15, 20, 25, 30, 35, and 40°C). The effect of temperature on conidial germination was also evaluated in different stages (hyaline versus pigmented conidia) of the species Lasiodiplodia theobromae. Conidial germination of Botryosphaeriaceae species infecting grapevines was significantly affected by temperature. Overall, conidial germination increased significantly with longer incubation times, especially from 2 to 12 h. In most cases, germination of conidia was not significantly different between 12 and 24 h incubation. Conidia of botryosphaeriaceous species did not germinate (with the exception of Botryosphaeria dothidea and Neofusicoccum parvum) at 5°C, and only B. dothidea, Diplodia seriata, and L. theobromae showed high levels of conidial germination at 40°C. Optimum conidial germination temperatures (defined as the temperature in which germination reached at least 50% in the shortest incubation time) were 25°C for B. dothidea and Dothiorella iberica, 25 to 30°C for Spencermartinsia viticola, 30°C for Diplodia corticola, D. mutila, D. seriata, N. parvum, and hyaline L. theobromae, and 40°C for pigmented L. theobromae conidia. Successful conidial germination of species of Botryosphaeriaceae infecting grapevines was always observed between 10 and 35°C with the exception of Dothiorella iberica and pigmented L. theobromae conidia, neither of which germinated at 35 and 10°C, respectively. Results of this study show conidia of botryosphaeriaceous species infecting grapevines to be capable of germination under a broad range of temperatures including those considered to be extreme, which may explain the success of these species as grapevine pathogens throughout most of the grape-growing areas in both Northern and Southern Hemispheres.

International audience; Esca, a Grapevine Trunk Disease (GTD), is of major concern for viticulture worldwide. Our study compares the fungal communities that inhabit the wood tissues of vines that expressed or not foliar esca-symptoms. The trunk and rootstock tissues were apparently healthy, whether the 10 year-old plants were symptomatic or not. The only difference was in the cordon, which contained white rot, a typical form of esca, in 79% of symptomatic plants. Observations over a period of one year using a fingerprint method, Single Strand Conformation Polymorphism (SSCP), and the ITS-DNA sequencing of cultivable fungi, showed that shifts occurred in the fungal communities colonizing the healthy wood tissues. However, whatever the sampling time, spring, summer, autumn or winter, the fungi colonizing the healthy tissues of asymptomatic or symptomatic plants were not significantly different. Forty-eight genera were isolated, with species of Hypocreaceae and Botryosphaeriaceae being the most abundant species. Diverse fungal assemblages, made up of potentially plant-pathogenic and -protective fungi, colonized these non-necrotic tissues. Some fungi, possibly involved in GTD, inhabited the non-necrotic wood of young plants, but no increase in necrosis areas was observed over the one-year period.