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Grapevine trunk diseases (GTDs) are the most widespread fungal diseases, affecting grapevines in all the major growing regions of the world, and their complete eradication is still not possible. Aiming to search alternatives to avoid the spread and high incidence of these diseases, the present work intended to molecularly identify the grapevine endophytic community, the phytopathogenic fungi associated with GTDs in vineyards within the Alentejo region, and to test potential antagonist microorganisms as biological control candidates against GTDs-associated fungi. Grapevine endophytic community showed a wide variety of fungi in GTDs’ asymptomatic and symptomatic plants, nine of them previously described as GTDs-associated fungi. GTDs prevalent fungi identified in symptomatic plants were Diaporthe sp., Neofusicoccum sp., and H. viticola. Almost all these fungi were also detected in asymptomatic plants, which shows the importance of investigating the interactions of fungal communities and confirms the need for early diagnosis of these diseases. Direct inhibition antagonism tests were performed among identified endophytes and GTDs phytopathogenic fungi, and all the endophyte fungi showed potential as biocontrol agents. Our findings suggest that endophytes are promising candidates for their use in biological control due to their antagonistic activity against the mycelia growth of some GTDs-associated fungi.

Grapevine trunk diseases (GTD) are caused by several fungal species and are major limiting factors to vineyard productivity and profitability in all viticulture areas. This study is aimed at addressing the gap in the knowledge with regards to measuring the long-term benefits of post-pruning fungicide application on trunk diseases incidence and crop yield in grape production systems. It also calculated the net economic benefit of implementing such practice over the vineyard lifespan. We selected a newly planted commercial table grape vineyard in the California desert and divided it in two blocks. In one block, the registered fungicide thiophanate-methyl was mechanically applied on pruning wounds for six consecutive years, while the other half remained untreated. Our results showed a significant lower GTD incidence and vine replants in treated blocks combined with a significant increase of total and marketable fruit. Potential annual economic benefits of applying fungicide on pruning wounds appear to be in the range of $8500–$12,500 per hectare annually in a 50–75% disease control scenario.

Grapevines exhibiting general decline symptoms were observed in July 2012 in Arbatan, a region in Marand county, north-western Iran. Leaf necrosis symptoms were also observed in affected grapevines. Dark brown necrotic lesions and wood discoloration were observed in the vascular tissues of affected cordons. Fungal isolates, all with similar cultural and morphological features, were obtained from symptomatic tissues. Morphological characteristics indicated that the isolates were Macrophomina phaseolina. Sequence analysis of the elongation factor (EF-1α) gene from isolates confirmed this identification, with 100% similarity to the reference M. phaseolina sequences obtained from GenBank. Pathogenicity assays of two M. phaseolina isolates on 2-year-old potted vines (cv. ‘Keshmeshi’) demonstrated that M. phaseolina was pathogenic on grapevine. This study confirmed the association of M. phaseolina with grapevine decline symptoms, and represents the first report of this fungus associated with grapevine trunk diseases in Iran.

Grapevines exhibiting general decline symptoms were observed in July 2012 in Arbatan, a region in Marand county, north-western Iran. Leaf necrosis symptoms were also observed in affected grapevines. Dark brown necrotic lesions and wood discoloration were observed in the vascular tissues of affected cordons. Fungal isolates, all with similar cultural and morphological features, were obtained from symptomatic tissues. Morphological characteristics indicated that the isolates were Macrophomina phaseolina. Sequence analysis of the elongation factor (EF-1α) gene from isolates confirmed this identification, with 100% similarity to the reference M. phaseolina sequences obtained from GenBank. Pathogenicity assays of two M. phaseolina isolates on 2-year-old potted vines (cv. 'Keshmeshi') demonstrated that M. phaseolina was pathogenic on grapevine. This study confirmed the association of M. phaseolina with grapevine decline symptoms, and represents the first report of this fungus associated with grapevine trunk diseases in Iran. [ABSTRACT FROM AUTHOR]

Balance between constitutive and induced responses provides plants flexibility to cope with biotic stresses. This study tested the hypothesis that invasion of grapevine wood by esca-associated fungi induces the production of defensive compounds as part of locally- and systemically-induced responses. In a vineyard, different symptomatic expressions of “Esca complex” in Vitis vinifera L. ‘Malvasia’ were evaluated in annual inspections. Then, levels of phenolics and fatty acids were determined in asymptomatic leaves of brown wood streaking (BWS) and grapevine leaf stripe (GLSD) vines, and in symptomatic leaves of GLSD and apoplectic vines; the results were compared with levels in healthy vines. In asymptomatic leaves of BWS and some GLSD vines, levels of phenolics decreased, independent of the total phenolic group. Such responses were usually associated with an increase in levels of linoleic, γ-linolenic and arachidonic acids, well-known signal transduction mediators. In symptomatic leaves, levels of phenolics increased, which is consistent with a locally-induced response; the onset of symptoms coincided with the highest increases e.g., 35% for quercetin-3-O-glucuronide. Thus, the long latency period between trunk invasion by fungi and visible foliar damage and the year-to-year fluctuation in symptomatic expressions observed with “Esca complex” might be partially attributed to a better utilization of constitutive defenses.

Grapevine trunk diseases (GTDs) are a major threat to the wine and grape industry. The aim of the study was to investigate the antifungal activity against Neofusicoccum parvum, Diplodia seriata, and Botryosphaeria dothidea of ε-polylysine, chitosan oligomers, their conjugates, Streptomyces rochei and S. lavendofoliae culture filtrates, and their binary mixtures with chitosan oligomers. In vitro mycelial growth inhibition tests suggest that the efficacy of these treatments, in particular those based on ε-polylysine and ε-polylysine:chitosan oligomers 1:1 w/w conjugate, against the three Botryosphaeriaceae species would be comparable to or higher than that of conventional synthetic fungicides. In the case of ε-polylysine, EC90 values as low as 227, 26.9, and 22.5 µg·mL−1 were obtained for N. parvum, D. seriata, and B. dothidea, respectively. Although the efficacy of the conjugate was slightly lower, with EC90 values of 507.5, 580.2, and 497.4 µg·mL−1, respectively, it may represent a more cost-effective option to the utilization of pure ε-polylysine. The proposed treatments may offer a viable and sustainable alternative for controlling GTDs.

There is evidence that secondary metabolites are involved in the fungal pathogenicity and virulence of Neofusicoccum spp. Fatty acids may also influence the plant⁻pathogen interaction but, so far, no information is available on their production by species of Neofusicoccum associated with Botryosphaeria dieback, which is a well-known syndrome of several plants with a complex etiology. In the present paper, the production of fatty acids in liquid medium, by strains of N. vitifusiforme and N. parvum associated with declining Sicilian vine plants, was evaluated. Data, acquired via gas chromatography⁻mass spectrometry (GC/MS), show the presence of linoleic acid as the most abundant fatty acid produced by both examined strains. In addition, the pathogenicity of N. vitifusiforme was tested on 2-year-old grapevine plants of cv. Inzolia.

Among grapevine diseases affecting European vineyards, Flavescence dorée (FD) and Grapevine Trunk Diseases (GTD) are considered the most relevant challenges for viticulture because of the damage they cause to vineyards. Unmanned Aerial Vehicle (UAV) multispectral imagery could be a powerful tool for the automatic detection of symptomatic vines. However, one major difficulty is to discriminate different kinds of diseases leading to similar leaves discoloration as it is the case with FD and GTD for red vine cultivars. The objective of this paper is to evaluate the potentiality of UAV multispectral imagery to separate: symptomatic vines including FD and GTD (Esca and black dead arm) from asymptomatic vines (Case 1) and FD vines from GTD ones (Case 2). The study sites are localized in the Gaillac and Minervois wine production regions (south of France). A set of seven vineyards covering five different red cultivars was studied. Field work was carried out between August and September 2016. In total, 218 asymptomatic vines, 502 FD vines and 199 GTD vines were located with a centimetric precision GPS. UAV multispectral images were acquired with a MicaSense RedEdge® sensor and were processed to ultimately obtain surface reflectance mosaics at 0.10 m ground spatial resolution. In this study, the potentiality of 24 variables (5 spectral bands, 15 vegetation indices and 4 biophysical parameters) are tested. The vegetation indices are selected for their potentiality to detect abnormal vegetation behavior in relation to stress or diseases. Among the biophysical parameters selected, three are directly linked to the leaf pigments content (chlorophyll, carotenoid and anthocyanin). The first step consisted in evaluating the performance of the 24 variables to separate symptomatic vine vegetation (FD or/and GTD) from asymptomatic vine vegetation using the performance indicators from the Receiver Operator Characteristic (ROC) Curve method (i.e., Area Under Curve or AUC, sensibility and specificity). The second step consisted in mapping the symptomatic vines (FD and/or GTD) at the scale of the field using the optimal threshold resulting from the ROC curve. Ultimately, the error between the level of infection predicted by the selected variables (proportion of symptomatic pixels by vine) and observed in the field (proportion of symptomatic leaves by vine) is calculated. The same methodology is applied to the three levels of analysis: by vineyard, by cultivar (Gamay, Fer Servadou) and by berry color (all red cultivars). At the vineyard and cultivar levels, the best variables selected varies. The AUC of the best vegetation indices and biophysical parameters varies from 0.84 to 0.95 for Case 1 and 0.74 to 0.90 for Case 2. At the berry color level, no variable is efficient in discriminating FD vines from GTD ones (Case 2). For Case 1, the best vegetation indices and biophysical parameter are Red Green Index (RGI)/ Green-Red Vegetation Index (GRVI) (based on the green and red spectral bands) and Car (linked to carotenoid content). These variables are more effective in mapping vines with a level of infection greater than 50%. However, at the scale of the field, we observe misclassified pixels linked to the presence of mixed pixels (shade, bare soil, inter-row vegetation and vine vegetation) and other factors of abnormal coloration (e.g., apoplectic vines).

Single plant replacement is one of the most commonly adopted practices to overcome vineyard crop decline associated with grapevine trunk diseases. A study was undertaken in long-term cultivated vineyards of an important wine producing district in northern Italy to investigate whether rhizosphere microbiome differed between adult and young replaced plants. Fungal and bacterial communities in adult and young replaced plants were investigated in ten vineyards across four geographic areas within the district. General and specific fungal and bacterial primers were used for PCR-DGGE and qPCR analysis. Moreover, quali-quantitative evaluation of Cylindrocarpon -like fungi, agents of foot rot belonging to the disease complex involved in vineyard decline, was performed with specific primers using nested PCR. Fungal and bacterial communities did not differ between adult and young plants, conversely they differed in geographic areas. While Pseudomonas and Bacillus communities varied mostly according to geographic origin, Ascomycota (microfungi) and Basidiomycota (white-rot fungi) also varied between the vineyards within each area. Furthermore, Cylindrocarpon -like species showed an ubiquitous occurrence, regardless plant age. Results show that long-term plant growth legacy overcomes plant age in shaping rhizosphere microbiome. Although composition of rhizosphere microbiome does not seem to represent a bio-indicator of vineyard decline according to findings of this study, the site-dependent variation of microbiome indicates that part of the complex phenomenon of crop decline may be due to a variable interaction between a series of soil biotic components and physiological state of grapevines. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Fifteen species of wood colonizing fungi are presented that have been collected from various non-Vitis hosts in the vicinity of vineyards located in southern Palatinate, Germany. Information is provided on their geographic distribution, epidemiology, host range, life strategy, symptoms and diagnosis. Their role as possible pathogens within the complex of grapevine trunk diseases (GTDs) is discussed. The following species are reported for the first time in Germany: Botryosphaeria sarmentorum, Cadophora malorum, Cadophora novi-eboraci, Collophora africana, Collophora hispanica, Cytospora chrysosperma, Diaporthe foeniculina, Dothiorella iberica, and Phaeoacremonium angustius. Diplodia seriata, Diplodia mutila, Dothiorella iberica, Cytospora chrysosperma, and Dothiorella iberica were proven by airborne inoculum, and could be demonstrated throughout the duration of our study, i.e. from March through September. The study points to a possible significance of non-Vitis hosts as additional inoculum source in GTDs. Also, the existence of airborne spores early in the year might be relevant with regard to the pruning period of vines. [ABSTRACT FROM AUTHOR]

Botryosphaeriaceae is a fungal family comprising many species involved in botryosphaeria dieback, a worldwide grapevine trunk disease. Currently, the interactions between Botryosphaeriaceae species and various grapevine cultivars are poorly understood and little data is available. This study investigated various life traits of five isolates belonging to four species of Botryosphaeriaceae found in French vineyards (Diplodia mutila, Diplodia seriata, Lasiodiplodia viticola and Neofusicoccum parvum). The two species N. parvum and L. viticola exhibited the highest optimal growth temperature and the best growth rates. They were also responsible for the most extensive necrosis and cankers in three Vitis vinifera cultivars (Cabernet Sauvignon, Merlot and Ugni-Blanc) that differed in susceptibility to botryosphaeria dieback, and in two genotypes resistant to downy and powdery mildew (RV4 and RV5). Identification of the extracellular toxins produced by isolates in culture media showed that the N. parvum isolate had a different metabolite profile from the others, producing terremutin and salicylic acid derivatives, which are known to be compounds associated with virulence. In a second step, life traits were associated with nondestructive monitoring of gene expression involved in the defence mechanisms of five grapevine cultivars and genotypes after inoculation of wood cuttings with Botryosphaeriaceae. The transcript analyses were carried out at different times and were associated with principal component analysis (PCA). Each cultivar presented a specific transcript signature and several transcripts were correlated either with the size of necrosis/cankers or with symptom reduction, thus offering useful markers for breeding or estimating the defence status of plants. [ABSTRACT FROM AUTHOR]

In most vineyards worldwide, agents of grapevine trunk diseases represent a real threat for viticulture and are responsible for significant economic loss to the wine industry. The conventional microbiological isolation technique used to diagnose this disease is tedious and frequently leads to false negatives. Thus, a dire need exists for an alternative method to detect this disease. One possible way involves infrared spectroscopy, which is a rapid, nondestructive analytical tool that is commonly used for quality control of feed stuffs. In the present work, a midinfrared spectrometer was tested as a fast tool for detecting agents of grapevine trunk disease. Midinfrared spectra were collected from 70 Vitis vinifera L. cv. Cabernet-Sauvignon one year old trunk-wood samples that were infected naturally in one viticulture nursery of the south of France. The samples underwent polymerase chain reaction and morphological identification, and the results were correlated to the midinfrared spectra by using multivariate analysis to discriminate between noninfected and infected samples. Based on comparison with some control samples, the highest percentage of correct identification of fungal contamination when using the midinfrared spectroscopy method is 80%. [ABSTRACT FROM AUTHOR]

A strain of Neofusicoccum parvum isolated from declining vines was pathogenic to grapevine cultivar Inzolia in Sicily. This strain produced some metabolites in liquid medium. Crude extract, through a bio-guided purification process, yielded four naphthalenone polyketides. They were identified by comparison with spectroscopic data and optical proprieties reported in literature as: (3S, 4S)-7-ethyl-3,4,8-trihydroxy-6-methoxy-3,4-dihydro-1-(2H)-naphthalenone, (3S*, 4S*)-3,4-dihydro-3,4,8-trihydroxy-7-(1-hydroxyethyl)-6-methoxy-1-(2H)-naphthalenone, (4S)-3,4-dihydro-4,8-dihydroxy-1-(2H)-naphthalenone, named botryosphaerones D and A, isosclerone, respectively, and (3S*,4S*)-3,4,5-trihydroxy-1-tetralone (1-4). Phytotoxic activity of the isolated compounds (1-4) was tested on grapevine leaves at using the leaf puncture assay. All tested compounds were phytotoxic, with botryosphaerone D showing the greatest activity. The phytotoxic effects decreased when treated leaves were exposed to light. All of the metabolites did not show in vitro antifungal activity against Diplodia seriata, Lasiodiplodia mediterranea, Neofusicoccum vitifusiforme, or Phytophthora citrophthora. This is the first report of in vitro production of botryosphaerones D and A, and 3,4,5-trihydroxy-1-tetralone by N. parvum.

Up to 60 species of fungi in the Botryosphaeriaceae family, genera Cadophora, Cryptovalsa, Cylindrocarpon, Diatrype, Diatrypella, Eutypa, Eutypella, Fomitiporella, Fomitiporia, Inocutis, Phaeoacremonium and Phaeomoniella have been isolated from decline-affected grapevines all around the World. The main grapevine trunk diseases of mature vines are Eutypa dieback, the esca complex and cankers caused by the Botryospheriaceae, while in young vines the main diseases are Petri and black foot diseases. To understand the mechanism of these decline-associated diseases and the symptoms associated with them, the toxins produced by the pathogens involved in these diseases were isolated and characterised chemically and biologically. So far the toxins of only a small number of these decline fungi have been studied. This paper presents an overview of the toxins produced by the most serious of these vine wood pathogens: Eutypa lata, Phaeomoniella chlamydospora, Phaeoacremonium aleophilum and some taxa in the Botryosphaeriaceae family, and examines how these toxins produce decline symptoms. The chemical structure of these metabolites and in some cases their vivotoxin nature are also discussed.

Background: Grapevine trunk diseases (GTDs) are a complex group of diseases that lead to major economic losses in all wine-producing countries. The investigation of biocontrol agents (BCAs) capable of forestalling or at least minimizing the development of GTDs has, recently, become a priority. Nursery experiments were set up to (i) assess the biocontrol effect of Trichoderma atroviride (Ta) SC1 and Bacillus subtilis (Bs) PTA-271, alone and in simultaneous application, against Botryosphaeria dieback (BOT)- and black-foot (BF)- associated pathogens during the grapevine propagation process and (ii) evaluate the success of the BCA inoculation during the grapevine propagation process, using quantitative reverse-transcription polymerase chain reaction techniques., Results: The results demonstrated a significant reduction in the percentage of potentially infected plants and the percentage of fungal isolation from wood fragments of BOT and BF pathogens in nursery material treated with Ta SC1 and Bs PTA-271, respectively. In one of the experiments, simultaneous treatments with Bs PTA-271 and Ta SC1 caused a reduction in percentages of potentially infected plants and fungal isolation, from wood fragments containing BOT and BF pathogens., Conclusion: These biological treatments may be relevant components of an integrated approach, using complementary management strategies to limit infection by GTD pathogens, but further research is still needed to elucidate the effectiveness of Bs PTA-271 and the benefits of simultaneous application with Ta SC1 for the control of GTD pathogens in nurseries. © 2022 Society of Chemical Industry., (© 2022 Society of Chemical Industry.)

Grapevine trunk diseases (GTDs) are serious threats in all viticultural areas of the world, and their management is always complex and usually inadequate. Fragmented and inconsistent information on the epidemiology and environmental requirements of the causal fungi is among the reasons for poor disease control. Therefore, we conducted a quantitative analysis of literature data to determine the effects of temperature on mycelial growth and the effects of temperature and moisture duration on spore germination. Using the collected information, we then developed mathematical equations describing the response of mycelial growth to temperature, and the response of spore germination to temperature and moisture for the different species and disease syndromes. We considered 27 articles (selected from a total of 207 articles found through a systematic literature search) and 116 cases; these involved 43 fungal species belonging to three disease syndromes. The mycelial growth of the fungi causing Botryosphaeria dieback (BD) and the esca complex (EC) responded similarly to temperature, and preferred higher temperatures than those causing Eutypa dieback (ED) (with optimal temperature of 25.3, 26.5, and 23.3°C, respectively). At any temperature, the minimal duration of the moist period required for 50% spore germination was shorter for BD (3.0 h) than for EC (17.2 h) or ED (15.5 h). Mathematical equations were developed accounting for temperature-moisture relationships of GTD fungi, which showed concordance correlation coefficients ≥0.888; such equations should be useful for reducing the risk of infection., Competing Interests: The author(s) declare no conflict of interest.

Grapevine trunk diseases (GTDs) are serious threats worldwide and are difficult to control, in part because the environmental requirements for epidemiological processes of the causal fungi are poorly understood. Therefore, we investigated the effects of temperature and moisture duration on spore germination of four fungi associated with two GTDs (esca complex and Eutypa dieback): Phaeomoniella chlamydospora , Phaeoacremonium minimum , Cadophora luteo-olivacea , and Eutypa lata . Conidia of Phaeomoniella chlamydospora , Phaeoacremonium minimum , and C. luteo-olivacea were similar: conidia of these fungi germinated profusely (>90%) between 20 and 30°C; Phaeomoniella chlamydospora and Phaeoacremonium minimum tended to germinate at higher temperatures (up to 40°C for P. minimum ), and C. luteo-olivacea at lower temperatures (as low as 5°C). E. lata ascospores germinated between 10 and 30°C. The required duration of moist periods for germination was shortest for C. luteo-olivacea (about 6 h), followed by P. minimum and E. lata (about 12 h) and Phaeomoniella chlamydospora (about 24 h). Further research on the environmental requirements of GTD fungi may increase our ability to predict infection periods and, thereby, improve disease control.

The viability of eight species of Botryosphaeriaceae pathogenic to grapevine was studied after a hot water treatment (HWT) in order to evaluate the feasibility of this technique as a potential tool to control these species during the grapevine propagation process. In a first trial (in vitro), mycelial plugs contained in Eppendorf tubes with sterile distilled water were subjected to different combinations of temperature (50–54°C) and exposure time (15, 30 and 45 min) in a hot water bath. Growth rates of treated mycelia were compared to untreated controls. Significant differences in survival and growth for all factors (species, temperature and time) and their 2-way interactions were observed. Fungal survival and growth generally decreased with increasing temperatures and exposure times. Diplodia seriata, Neofusicoccum luteum, N. parvum and Spencermartinsia viticola were the most susceptible species to temperature, while Lasiodiplodia theobromae and N. vitifusiforme were the most tolerant. In a second trial (in planta), the fungi were inoculated into grapevine canes (Richter 110 rootstock). Inoculated canes were incubated at 25°C for 3 weeks to allow the fungi to colonize the wood and then subjected to HWT in the range of 50–53°C for 30 min, and survival of fungi after HWT was assessed. Survival of all species was sharply reduced after HWT of 30 min at 51°C and higher temperatures. At 50°C, Lasiodiplodia theobromae was the most tolerant species whereas N. luteum was the most susceptible. Results obtained in this study demonstrate the feasibility of controlling these pathogens by HWT in the nursery grapevine propagation process.

Little is known about the pathogenicity and etiology of Hymenochaetales taxa associated with esca in South Africa. Ten South African Hymenochaetales taxa associated with esca in grapevine were subjected to basic enzyme assays to determine which ligninolytic enzymes were secreted by each taxon. In addition, a field trial was undertaken to determine the pathogenicity of these taxa. Twenty-seven fungal isolates and two negative controls were inoculated into wounds made on mature grapevines of the cultivars Shiraz and Mourvédre. Inoculated vines were evaluated for white rot symptoms after 24 months. The results of the enzyme assays indicated a difference in enzyme secretion among taxa and also between isolates of the same taxa. All isolates secreted cellulase and laccase, but there was a difference in isolates’ ability to secrete manganese peroxidase and lignin peroxidase. The results of the pathogenicity trial showed that all of the isolates used were capable of causing the characteristic white rot symptom in the wood. There were clear differences in susceptibility to white rot between the two cultivars tested, namely Shiraz and Mourvédre. The cultivars also differed in which taxa proved to be more virulent. On Shiraz a specific isolate of Taxon 6 (an Inonotus sp.), Phellinus sp. and Inonotus setuloso-croceus were significantly virulent. On Mourvédre, Taxon 3 (an Inocutis sp.) was significantly virulent.

The antagonistic activity of 46 bacterial strains isolated from Bordeaux vineyards were evaluated against Phaeomoniella chlamydospora , a major grapevine pathogen involved in Esca. The reduction of the necrosis length of stem cuttings ranged between 31.4% and 38.7% for the 8 most efficient strains. Two in planta trials allowed the selection of the two best strains, Bacillus pumilus (S32) and Paenibacillus sp. (S19). Their efficacy was not dependent on application method; co-inoculation, prevention in the wood and soil inoculation were tested. The involvement of antibiosis by the secretion of diffusible and/or volatile compounds in the antagonistic capacity of these two strains was assessed in vitro . Volatile compounds secreted by B. pumilus (S32) and Paenibacillus sp. (S19) were identified by gas chromatography/mass spectroscopy (GC/MS). The volatile compounds 1-octen-3-ol and 2,5-dimethyl pyrazine were obtained commercially and tested, and they showed strong antifungal activity against P. chlamydospora , which suggested that these compounds may play an important role in the bacterial antagonistic activity in planta . Furthermore, the expression of 10 major grapevine defense genes was quantified by real-time polymerase chain reaction, which demonstrated that the two strains significantly affected the grapevine transcripts four days after their application on the plants. High expression levels of different genes associated with P. chlamydospora infection in B. pumilus pre-treated plants suggests that this strain induces systemic resistance in grapevine. For the first time, we demonstrated the ability of two bacterial strains, B. pumilus and Paenibacillus sp., isolated from grapevine wood, to control P. chlamydospora via direct and/or indirect mechanisms. [ABSTRACT FROM AUTHOR]

Thirteen species of lesser known wood inhabiting fungi living on grapevine (Vitis vinifera) and/or in the vicinity of vineyards are presented with respect to systematics, life strategy and symptoms, host range, geographic distribution, transmission and occurrence on Vitis, identification, and diagnosis. Sampling has been performed during a three-year-survey covering nurseries, vineyards, and neighboring fruit trees in the viticultural area of southern Palatinate, Germany. The possible pathogenic significance and the relation to grapevine trunk diseases are discussed. The following species are reported for the first time in Germany: Cadophora luteo-olivacea, C. fastigiata, Collophora paarla, Coniochaeta hoffmannii, Eucasphaeria capensis, Phomopsis cotoneastri, and the Esca-related Phaeoacremonium viticola and P. fraxinopennsylvannicum. Eucasphaeria capensis and Phomopsis cotoneastri are reported for the first time from Vitis worldwide. [ABSTRACT FROM AUTHOR]

Species of Botryosphaeriaceae are important wound pathogens of grapevines as causal agents of botryosphaeria dieback, but the behaviour of their conidia pre-infection is unknown and may be important for disease development. Adhesion properties of conidia were investigated for Botryosphaeria dothidea, Neofusicoccum luteum and N. parvum on substrata with different affinities for water. Greatest adhesion on any surface was reached after 5 min for isolates N. luteum MM558, B. dothidea 007 and N. parvum G652 (53·1, 54·0 and 50·6%, respectively) and for N. luteum isolate CC445 after 20 min (61·4%). As conidia adhered well to all artificial substrata, it appeared as if the attachment process was nonspecific. Overall, surface wettability did not play a major role in the adhesion of conidia. Spore surface proteins appeared to play a role in the adhesion process because treatment of conidia of N. luteum MM558 with a protease completely prevented adhesion. Histochemical labelling of conidia and germlings with Coomassie brilliant blue (specific for proteins) was positive for all isolates, with a blue 'halo' often seen surrounding conidia or near the germ tube emergence point after incubation times conducive to germination. Alcian blue also stained material surrounding conidia after longer incubation times, which indicated that mucopolysaccharide and protein production may be involved in a second phase of adhesion. [ABSTRACT FROM AUTHOR]

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 . [ABSTRACT FROM AUTHOR]

Background and Aims The application of Trichoderma species on grapevine pruning wound surfaces reduces wound infection from trunk pathogens that cause grapevine decline. The aim of this study was to determine the efficacy of pruning wound treatments containing Trichoderma as influenced by the time of pruning and time of application following pruning. Methods and Results Cultivars Chenin Blanc and Cabernet Sauvignon were pruned early and late in the winter season, respectively, corresponding to the break from the winter dormancy period and the normal pruning time for these cultivars. After pruning, the wounds were treated immediately, 6, 24, 48 or 96 h after pruning with either T. atroviride or T. harzianum. Colonisation of grapevine pruning wounds by the Trichoderma spp. was dependent on the physiological state of the vines as well as the weather conditions at pruning. In dormant vines, colonisation remained high from immediate application up to 48 h after pruning. In vines at break of dormancy, colonisation was highest at 6 and 24 h after application. Natural wound infection was higher in wounds pruned in late winter compared with that in early winter. Conclusions Applying the biocontrol agent 6 h after pruning consistently resulted in a high incidence of Trichoderma spp. in both cultivars at either early or late pruning regardless of vine physiological state or the weather conditions. Significance of Study Pruning early in the season in combination with the application of Trichoderma spp. pruning-wound agents approximately 6 h after pruning can significantly reduce wound infection by trunk pathogens. [ABSTRACT FROM AUTHOR]

A strain of Neofusicoccum parvum isolated from declining vines was pathogenic to grapevine cultivar Inzolia in Sicily. This strain produced some metabolites in liquid medium. Crude extract, through a bio-guided purification process, yielded four naphthalenone polyketides. They were identified by comparison with spectroscopic data and optical proprieties reported in literature as: (3S, 4S)-7-ethyl-3,4,8-trihydroxy-6-methoxy-3,4-dihydro- 1-(2H)-naphthalenone, (3S*, 4S*)-3,4-dihydro-3,4,8-trihydroxy-7-(1-hydroxyethyl)-6-methoxy-1-(2H)-naphthalenone, (4S)-3,4-dihydro-4,8-dihydroxy-1-(2H)-naphthalenone, named botryosphaerones D and A, isosclerone, respectively, and (3S*,4S*)-3,4,5-trihydroxy-1-tetralone (1-4). Phytotoxic activity of the isolated compounds (1-4) was tested on grapevine leaves at using the leaf puncture assay. All tested compounds were phytotoxic, with botryosphaerone D showing the greatest activity. The phytotoxic effects decreased when treated leaves were exposed to light. All of the metabolites did not show in vitro antifungal activity against Diplodia seriata, Lasiodiplodia mediterranea, Neofusicoccum vitifusiforme, or Phytophthora citrophthora. This is the first report of in vitro production of botryosphaerones D and A, and 3,4,5-trihydroxy-1-tetralone by N. parvum. [ABSTRACT FROM AUTHOR]

Inoculum longevity of Diplodia seriata occurring in grapevine pruning debris was studied to determine its role as a potential source for new infections on grapevines. Pruned canes naturally colonised by D. seriata were collected 2 years after pruning and kept outdoors in an experimental vineyard under natural conditions. Conidia production was monitored at the collection time and 6, 12 and 18 months later. In each monitoring period, the percentage of pycnidia containing conidia, the estimated average amount of conidia per pycnidium and the conidial germination percentage were assessed. A significant decrease in the percentage of pycnidia containing conidia was observed throughout the experiment. The average amount of conidia per pycnidium was reduced significantly, from 270 conidia per pycnidium 24 months after pruning, down to 25 conidia per pycnidium at the end of the assessment period. Germination percentage of conidia also decreased significantly, from 63 to 44 % within the same period. Overall, these results confirmed the reduction in the D. seriata inoculum available from the pruning debris through all the studied variables. However, 42 months after pruning viable conidia of D. seriata were still detected, thus revealing that pruning debris may become an important long-lasting inoculum source. [ABSTRACT FROM AUTHOR]

Botryosphaeria dieback is an important grapevine trunk disease with global impact. Susceptibility differences between grape varieties manifest as different expression of canopy symptoms in the field. However, the cause of these dieback symptoms and their relation with wood necrosis remain only partially understood. As a first step towards future strategies for resistance breeding, wood necrosis was investigated over a large selection of the Vitaceae family members following artificial inoculation of the Botryosphaeriaceae fungi Neofusicoccum parvum and Diplodia seriata into woody internodes. Large variation of resistance levels was found, with good performance in several accessions from V. vinifera subsp. sylvestris, the ancestor of cultivated grapevine. To get insight into the mechanisms of this apparent resistance, expression of defence genes was studied in V. vinifera cv. Chardonnay, Gewürztraminer and different V. vinifera subsp. sylvestris genotypes, in both green and necrotic areas of inoculated woods. Resistance to Botryosphaeriaceae in V. vinifera subsp. sylvestris correlated with earlier and higher induction of some defence genes, both in green and necrotic wood. Moreover, leaves of several V. vinifera subsp. sylvestris accessions were also less susceptible to necrosis induced by treatment with a culture filtrate of Botryosphaeriaceae, compared to commercial cultivars of V. vinifera. The results show that V. vinifera subsp. sylvestris provides interesting genetic resources for breeding new varieties with enhanced resistance to botryosphaeria dieback. [ABSTRACT FROM AUTHOR]

Antibiosis has been shown to be an important mode of action by Trichoderma species used in the protection of grapevine pruning wounds from infection by trunk pathogens. The major active compound from Trichoderma isolates known to protect grapevine pruning wounds from trunk pathogen infection was isolated and identified. The compound, a 6-pentyl- α-pyrone (6PP), was found to be the major secondary metabolite, by quantity, which accumulated in the culture filtrate of T. harzianum isolate T77 and the two T. atroviride isolates UST1 and UST2. Benzimidazole resistant mutants generated from these isolates also produced 6PP as their main secondary metabolite, except for a mutant of T77 that had lost its ability to produce 6PP. The isolates UST1 and UST2 were co-cultured with the grapevine trunk pathogens Eutypa lata and Neofusicoccum parvum in a minimal defined medium and a grapevine cane-based medium ( GCBM). Co-culturing UST1 with N. parvum induced 6 PP production in the minimal defined medium and the GCBM. The production of 6 PP by UST2 was induced in the GCBM, while co-culturing with the two trunk pathogens either reduced or had no effect on 6 PP production. Mycelial growth and ascospore/conidia germination of E. lata, N. australe, N. parvum and Phaeomoniella chlamydospora were inhibited by 6 PP in a concentration-dependent manner. The results show that the presence of N. parvum and grapevine wood elicits the production of 6 PP, suggesting that this metabolite is involved in Trichoderma-pathogen interactions on grapevine pruning wounds. [ABSTRACT FROM AUTHOR]

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 B. 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. [ABSTRACT FROM AUTHOR]

The 9th International Workshop on Grapevine Trunk Diseases was held in Adelaide, Australia, 18–20 November, 2014. The meeting was attended by 111 participants and 71 papers were presented either as oral or poster presentations in four sessions: Pathogen Identification and Detection, Epidemiology, Host-Pathogen Interactions and Disease Management. A field trip to the Barossa Valley wine region was undertaken to showcase proactive management of grapevine trunk diseases in Australia. The workshop is the 9th organised by members of the International Council on Grapevine Trunk Diseases (www.icgtd.org), a subject matter committee of the International Society for Plant Pathology (www.isppweb.org).