Eutypa Lata Research Articles

Evaluation of Pruning Wound Protection Products for the Management of Almond Canker Diseases in California.

Almond trunk and branch canker diseases constitute a major cause of tree mortality in California. Numerous fungal pathogens have been associated with these canker diseases and pruning wounds act as major infection courts. Before this study, there were no products registered in California for the management of these diseases. In this study, fungicidal products including synthetic chemistries, biocontrols, paint, and a sealant were evaluated for preventing fungal pathogen infection via pruning wounds. In four field trials conducted over two dormant seasons, 16 pruning wound treatments were tested using handheld spray applications against five almond canker pathogens, namely Botryosphaeria dothidea, Neofusicoccum parvum, Cytospora sorbicola, Ceratocystis destructans, and Eutypa lata. The fungicide thiophanate-methyl (Topsin M; United Phosphorus, Bandra West, Mumbai, India) provided 82% overall disease prevention against four fungal pathogens. The biological control agent, Trichoderma atroviride SC1 (Vintec; Bi-PA, Londerzeel, Belgium), tested at three application rates, resulted in 90 to 93% protection of pruning wounds in field trials, and for individual pathogens ranged from 81 to 100% protection for the three rates. At the time of this publication, Vintec is being considered for registration as a biological control product for the prevention of almond canker diseases, while Topsin M is recommended to growers for the prevention of almond canker diseases. This research indicates that effective protection of pruning wounds from infection by almond canker pathogens can be achieved with a one-time spray application of thiophanate-methyl or the biocontrol T. atroviride SC1 (recommended 2 g/liter) after pruning.

First report of Eutypa lata causing cankers and dieback in sweet cherry in Chile.

Sweet cherry (Prunus avium) is one the most important fruit crops in Chile. Its production has significantly grown in recent years, reaching 228,448 tons exported in 2019/2020, to 47 countries. One of the main threats for this expanding crop are fungal pathogens, especially those that cause wood diseases. Cherry orchards (n=35) located in the central area of Chile, from Curicó (34°58'58''S 71°14.366'W) to Angol (37°47'42.7''S 72°42.982'W), were surveyed during 2020. Wood samples were collected (n= 72) from living branches and trunks showing dieback, cankers and dark necrosis, mostly wedge shaped. Small wood sections (0.5-cm) were cut off from the margin of the necrosis and surface disinfected using 0.5% v/v sodium hypochlorite. Sections were plated on a quarter-strength potato dextrose agar amended with 1mg/L tetracycline (PDA-tet). Plates were incubated at 25°C until mycelial development and subsequently the isolates were purified transferring excised fungal tips to PDA. Colonies (n=21) developed white cottony mycelia, which turned slightly greyish and flatter after 10-days at 25°C. Isolates developed black pycnidia which released beige conidial matrixes after subsequent 15-days at 25 +/-2°C and 12-h photoperiod. Conidia were hyaline, curved and filiform, measuring 19.8-(27.9)-36.7 μm length (lineal) x 1.2-(1.7)-1.9 μm width (n=70), according to Eutypa lata (Rappaz, 1984). DNA was extracted from mycelia of the representative isolates HMCe30a, HMCe41a, HMCe109c and HMCe110a. The partial β-tubulin gene was amplified using bt2A/bt2B primers (Glass & Donaldson 1995) and the internal transcribed spacer region was amplified using ITS1/ITS4 primers (White et al. 1990). Sequences were BLAST analyzed, finding that ITS shared 99% and βTUB 100% identity with E. lata strain CBS 208.87 (Rolshausen et al. 2006). Sequences were accessioned to GenBank (MW363035, MW363034, MW363033 and MW363032 [ITS], and MW366820, MW366819, MW366818and MW366817 [βTUB]). The isolates were inoculated on sweet cherry healthy plants cv. Kordia, produced by rooting scions in tap water amended with 500 ppm of indole-butyric acid, for 30 days. An injury was made in the upper third of the shoot using a sterile 0.5-cm diameter corkborer. Mycelial plugs were placed on the injuries and covered with plastic film, using sterile agar for controls (n=25). Plants were incubated in aerated tap water for 60 days at 23 +/-3 °C. After incubation, plants were cut exposing dark-brown necrotic lesions, while control plants remained asymptomatic. Moreover, 2-year old potted plants cv. Lapins were inoculated (n=3 per isolate) with mycelial plugs, on fresh cuts of their main lateral branches, in January 20th, and remained under partial shade for 72-days. After incubation, bark was removed from inoculated branches and the necrotic lesions length was measured. HMCe109c was the most virulent isolate (3.6 cm), followed by HMCe30a (2.1 cm), HMCe41a (1.9 cm) and HMCe110a (1.1 cm), while symptoms were not reproduced in controls. Fulfilling Koch's postulates, fungi were reisolated from all inoculated plants in both pathogenicity tests and no fungus was recovered from controls. To our knowledge this is the first report of Eutypa lata causing wood decay in sweet cherry in Chile. The pathogen was recently reported causing dieback of grapevines in Chile (Lolas et al. 2020). These are significant findings due to the frequent proximity of sweet cherry orchards and vineyards, which facilitates cross infections.

Pre-Symptomatic Disease Detection in the Vine, Chrysanthemum, and Rose Leaves with a Low-Cost Infrared Sensor

Thermography is a technique based on infrared imaging, which is used nowadays to detect plants under stress caused by biotic and abiotic factors. In many cases, temperature changes have already been correlated with pathogen attacks. In this sense, thermography offers the ability of early disease detection in plant pathology. In this work, a low-cost AMG8833 Grind-Eye infrared camera combined with a 1080P RGB web camera was used to develop an integrated infrared and RGB imaging system, to record temperature changes on vine, chrysanthemum, and rose plant leaf surfaces. Vine and chrysanthemum leaves were infected with Phomopsis viticola and Septoria ssp. respectively, respectively, whereas rose plants leaves were infected with Colletotrichum spp. as well as with Podosphaera pannosa. Measurements were performed using the integrated imaging system on infected and uninfected leaves, as well as on PDA plates with active and non-active mycelium. According to the results, vine leaf tissue infected with P. viticola and rose plants leaf tissue infected with P. pannosa had a pre-symptomatic (four days after infection) decrease in temperature up to 1.6 and 1.1 °C, respectively, compared with uninfected tissue. In contrast chrysanthemum leaf tissue infected with Septoria ssp. and rose plant leaf tissue infected with Colletotrichum spp. had a pre-symptomatic (four days after infection) increased temperature up to 1.1 °C and 1.0 °C, respectively, compared with uninfected tissue. In vitro measurements showed that the active fungi mycelium had approximately 1.1 to 2.1 °C lower temperature than the non-active mycelium. The results above show that the integrated infrared and RGB imaging system developed in this work can be used to detect early disease infection before visible symptoms appeared, facilitating the decision-making process.

The Influence of Water Deficit Stress on the Grapevine Trunk Disease Pathogens Eutypa lata and Diplodia seriata.

The increasing prevalence of the grapevine trunk diseases Eutypa and Botryosphaeria dieback has been attributed, in part, to abiotic stresses imposed on vineyards as production intensifies worldwide. The aim of this study was to evaluate the influence of water deficit irrigation practices on the infection of pruning wounds by Eutypa lata and Diplodia seriata and the subsequent rate of colonization. Two vineyard trials were conducted over two consecutive seasons in South Australia, one in the Riverland with 'Cabernet Sauvignon' with four irrigation treatments (100, 50, 25, and 12.5% of the standard irrigation program) and another in the Barossa Valley with 'Shiraz' on six rootstocks and own roots, either irrigated or not irrigated. According to leaf water potential assessments, vines with reduced irrigation were generally in water deficit and therefore subjected to stress. On the whole, incidence of wound infection and distance of colonization were similar between irrigation treatments for both pathogens, except in the Riverland, where E. lata colonized canes to a greater extent in well-watered vines than those in water deficit. Only vines on rootstock 'Ramsey' in the Barossa Valley had greater extent of colonization by E. lata in the nonirrigated vines. There was no correlation between internal staining and colonization, with both pathogens recovered to nearly 20 cm ahead of the staining. Water deficit did not increase the susceptibility of grapevine pruning wounds to infection or colonization of the subtending tissue by E. lata and D. seriata. In fact, there was evidence of lower susceptibility to colonization by E. lata in vines subjected to severe water deficit.

Mating types of Phomopsis viticola isolates from grapevine in Aegean Region/Turkey

Mating types of Phomopsis viticola isolates from grapevine in Aegean Region/Turkey

Evaluation of Cultivars and Spray Programs for Organic Grape Production in Virginia

The French American hybrid grape cultivars Corot noir and Arandell (Vitis sp.), and Vidal blanc and Petit Manseng (Vitis vinifera), along with different spray programs, were evaluated for potential organic production in Virginia from 2013 to 2014. Results obtained in the study demonstrate that organic wine grape production in Virginia can be achieved by using select grape cultivars and spray programs. With the exception of Vidal blanc, disease severity and disease incidence were below the threshold for maintaining healthy vines in all organically managed grape cultivars. ‘Vidal blanc’ was not sufficiently resistant to downy mildew (Plasmopara viticola), precluding it from potential organic management in Virginia. The study also demonstrated significant disease resistance in Virginia of the cultivar Arandell, released by Cornell University (Ithaca, NY) in 2013. The results suggest that the organically registered fungicide Bacillus subtilis is effective in reducing the severity and incidence of black rot (Guignardia bidwellii) and phomopsis cane and leaf spot (Phomopsis viticola). The chemistry of organically managed berries harvested in 2014 met minimum requirements for wine production with soluble solids, titratable acidity, and pH ranging from 18.7% to 20.2%, 7.6 to 8.0 g·L−1, and 3.3 to 3.4, respectively, in ‘Arandell’ and ‘Corot noir’; and 21.0% to 24.4%, 7.8 to 9.6 g·L−1, and 2.7 to 2.9, respectively, in ‘Petit Manseng’ and ‘Vidal blanc’ juice.

Assessment of canopy size using UAV-based point cloud analysis to detect the severity and spatial distribution of canopy decline

This study aimed to validate the use of UAV-based point cloud analysis to detect canopy decline severity and its spatial distribution in vineyards.A new approach to assess canopy decline, caused by Eutypa dieback-like symptoms, using unmanned aerial vehicle (UAV) remote sensing was compared with ground visual assessment in the vineyard. Canopy point cloud captured by UAV-based imagery during the growing season was analysed by a customized program to determine canopy decline severity and spatial distribution in a symptomatic Shiraz vineyard in Eden Valley, South Australia. Experienced assessors performed a ground visual assessment in the vineyard at E-L stage 15. k-means clustering was used to detect reduced canopy volume due to Eutypa dieback-like symptoms. Results from point cloud analysis showed that 12.5 % of the total canopy length in the vineyard had Eutypa dieback symptoms while the ground visual assessment detected 11.4 %. Confusion matrix results showed an accuracy of 87.4 % and a kappa coefficient of 0.43 compared with ground visual assessments. Additionally, automatic analysis of the point cloud was quicker than the ground visual assessment and generated precise geographic coordinates of the symptomatic canopy sections. Point cloud analysis can detect Eutypa dieback-like symptoms and its spatial distribution with 87.4 % accuracy, compared with the ground assessment. Similar to ground visual assessment, E-L stage 15 appears to be a suitable stage to apply point cloud analysis to make Eutypa dieback-like symptom assessments. Grapevine canopy decline, caused by various factors such as Eutypa dieback and inadequate management, can cause yield reduction and threaten vineyard longevity. Compared with tedious ground visual assessments, point cloud analysis can accelerate the assessment of canopy decline in vineyards and help with the planning of remedial practices using precise geographic coordinates of the affected sections.

DNA-based detection of grapevine trunk-disease pathogens from environmental spore samples

In California vineyards, spore dispersal of fungi that cause grapevine trunk diseases Botryosphaeria dieback and Eutypa dieback occurs with winter rains. Spores infect through pruning wounds made to the woody structure of the vine in winter. Better timing of preventative practices that minimize infection may benefit from routine spore-trapping, which could pinpoint site-specific time frames of spore dispersal. To speed pathogen detection from environmental spore samples, we identified species-specific PCR primers and protocols. Then we compared the traditional culture-based method versus our new DNA-based method.•PCR primers for Botryosphaeria-dieback pathogen Neofusicoccum parvum and Eutypa-dieback pathogen Eutypa lata were confirmed species-specific, through extensive testing of related species (in families Botryosphaeriaceae and Diatrypaceae, respectively), other trunk-disease pathogens, and saprophytic fungi that sporulate in vineyards.•Consistent detection of N. parvum was achieved from spore suspensions used fresh or stored at -20°C, whereas consistent detection of E. lata was achieved only with a new spore-lysis method, using zirconia/silica beads in a FastPrep homogenizer (MP Biomedicals; Solon, Ohio, USA), and only from spore suspensions used fresh. Freezing E. lata spores at -20°C made detection inconsistent.•From environmental samples, spores of E. lata were detected only via PCR, whereas spores of N. parvum were detected both via PCR and in culture.

Effect of nutrients on cellulolytic and pectolytic enzyme production of Phomopsis viticola a leaf spot pathogen of grapes (vitis vinifera)

Phomopsis viticola causes leaf spot disease to the Grapes plant is a potential pathogen of Grapes plant (Vitis Vinifera), was isolated from diseased Vitis Vinifera leaves from Nashik district and used for the present study. Pathogen was grown on the Czapek-Dox liquid medium substituting or adding different carbon, nitrogen to study cellulolytic and pectolytic enzyme production and total phenol production. The activity of enzyme was observed on the 8th day of incubation period. A grate extent of growth variation was observed on different carbon, nitrogen. Among the carbon source, maximum growth on Glucose followed by Control, lactose, fructose and dextrose while in absence of carbon source there was no growth. From nitrogen source maximum growth on nickel nitrate. While barium nitrate, cobalt nitrate and control had more or less similar effect on the growth. The least growth was observed in potassium nitrate. In absence of nitrogen source in the medium resulted in lowest growth as compared to other compound. Nitrogen sources shows much variation in cellulolytic enzyme activity. The cellulose activity was maximum in nickel nitrate and minimum in barium nitrate and potassium nitrate as compare to cobalt nitrate and control.

A comparison of the metabolomic response of grapevine to infection with ascomycete wood-infecting fungi

Fungi that cause grapevine trunk diseases, including Diplodia seriata, Eutypa lata, Neofusicoccum parvum, and Phaeomoniella chlamydospora, all colonize woody tissues, but lesions develop to different extents. Such variation is thought to correspond to fungal virulence, but it may also reflect host metabolic responses to limit colonization. From the woody stems of potted Vitis vinifera ‘Cabernet-Sauvignon’ in the greenhouse, we measured wood lesions and quantified metabolites at the lesion margins. Amino acids, sugars, phenolics, and terpenoids were quantified by appropriate chromatography techniques. At 3 months post-inoculation (MPI) lesions from P. chlamydospora and N. parvum were larger than those of D. seriata and E. lata. Among all pathogen treatments, compared to controls, lower concentrations of terpenoids at 0.5 MPI were followed at 2 MPI by higher concentrations of some phenolic compounds. Lesion length did not correlate with primary metabolites, but larger lesions did correlate with higher phenolic concentrations and lower terpenoid concentrations.

Fungal Pathogens Associated With Canker Diseases of Almond in California.

Almond canker diseases are destructive and can reduce the yield as well as the lifespan of almond orchards. These diseases may affect the trunk and branches of both young and mature trees and can result in tree death soon after orchard establishment in severe cases. Between 2015 and 2018, 70 almond orchards were visited throughout the Central Valley of California upon requests from farm advisors for canker disease diagnosis. Two major canker diseases were identified, including Botryosphaeriaceae cankers and Ceratocystis canker. In addition, five less prevalent canker diseases were identified, including Cytospora, Eutypa, Diaporthe, Collophorina, and Pallidophorina canker. Seventy-four fungal isolates were selected for multilocus phylogenetic analyses of internal transcribed spacer region ITS1-5.8S-ITS2 and part of the translation elongation factor 1-α, β-tubulin, and glyceraldehyde 3-phosphate dehydrogenase gene sequences; 27 species were identified, including 12 Botryosphaeriaceae species, Ceratocystis destructans, five Cytospora species, Collophorina hispanica, four Diaporthe species, two Diatrype species, Eutypa lata, and Pallidophorina paarla. The most frequently isolated species were Ceratocystis destructans, Neoscytalidium dimidiatum, and Cytospora californica. Pathogenicity experiments on almond cultivar Nonpareil revealed that Neofusicoccum parvum, Neofusicoccum arbuti, and Neofusicoccum mediterraneum were the most virulent. Botryosphaeriaceae cankers were predominantly found in young orchards and symptoms were most prevalent on the trunks of trees. Ceratocystis canker was most commonly found in mature orchards and associated with symptoms found on trunks or large scaffold branches. This study provides a thorough examination of the diversity and pathogenicity of fungal pathogens associated with branch and trunk cankers of almond in California.

Pruning-wound protectants for trunk-disease management in California table grapes

In California's Mediterranean climate, management of grapevine trunk diseases (Botryosphaeria dieback, Eutypa dieback, Phomopsis dieback, Esca) focuses on protecting vines during the dormant season, when pruning coincides with rain-induced spore dispersal of the causal fungi (‘trunk pathogens’). Applying protectants (fungicides, toxic barriers, sealants, biocontrol agents) after pruning can minimize infection of pruning wounds. For the dormant seasons of 2017–2019, in a 2-year-old Vitis vinifera ‘Scarlet Royal’ vineyard in the southern San Joaquin Valley, we evaluated tractor-spray applications of the following protectants labeled for table grapes: fluopyram + tebuconazole, pyraclostrobin + boscalid, thiophanate-methyl + myclobutanil, and Bacillus amyloliquefaciens. A comprehensive set of virulent and widespread trunk pathogens, including Diaporthe ampelina, Eutypa lata, Neofusicoccum parvum, and Phaeomoniella chlamydospora, were inoculated to pruning wounds post-application, with detection attempts after a 3 to 4-week incubation period (before budbreak). Consistently high efficacies of pyraclostrobin + boscalid (68–100% and 56–100%, respectively) and thiophanate-methyl + myclobutanil (64–77% and 91–100%, respectively) against Botryosphaeria-dieback pathogen N. parvum and Phomopsis-dieback pathogen D. ampelina suggest spray applications of these protectants could minimize infection by these common trunk pathogens. Low and variable detection rates of slow-growing Eutypa-dieback pathogen E. lata and Esca pathogen P. chlamydospora suggest that the incubation period should be longer or that more replication is needed. Low efficacy of B. amyloliquefaciens, especially with only 4 days in 2017 before pathogen inoculation, suggests this biological-control agent may need more time and/or repeated applications to become established on pruning wounds before being challenged by a pathogen.

Ecological Microclimate Influence on Grapevine Phomopsis viticola Attack Frequency in Aiud-Ciumbrud Vineyards

Phomopsis viticola (Sacc.) Sacc. (syn. Cryptosporella viticola Shear, Diaporthe viticola Nitschke, Diplodia viticola Desm, Fusicoccum viticolum Reddick, Phoma flaccida Viala & Ravaz, Phoma viticola Sacc.), is the causal agent of the grapevine disease named ‘Phomopsis cane’ and ‘Leaf spot’ in the U.S.A. or ‘Excoriose’ in Europe. This study aims to evaluate the influence of the microclimate on Phomopsis viticola attack in Aiud-Ciumbrud vineyards. The observations were done on four plots in Aiud-Ciumbrud vineyards in the period March-August 2020. Up to the end of August 2020, ten treatments with contact and systemic products based on metiram and sulphour were done together with the other standard agro-technological operations. In the ecological conditions of spring-summer 2020, with higher temperature than the average in January, February, March and June, more rain than the average in February, March and June and less rain in January, April and May, we found frequency of the excoriosis in the range of 4%-12% at the beginning of the season. After the fungicide treatments, the attack frequency decreased up to 0%-7%. In the present research work, we show that in Aiud-Ciumbrud vineyards Phomopsis viticola attack was present and influenced by the microclimate conditions and also it was reduced by the fungicide treatments.

Incidence and severity of Eutypa dieback in grapevines are related to total surface area of pruning wounds

Incidence and severity of Eutypa dieback in grapevines are related to total surface area of pruning wounds

Aetiology of branch dieback, panicle and shoot blight of pistachio associated with fungal trunk pathogens in southern Spain

AbstractPistachio represents an emerging nut crop across the Mediterranean basin. In Spain, pistachio has been traditionally cultivated in marginal‐dry areas with unfavourable climatic conditions for plant diseases. Consequently, little attention has been given to research on pistachio diseases until recently. Symptoms of branch dieback and cankers, and shoot and panicle blight have been recently observed in commercial pistachio orchards across southern Spain. In this study, 10 commercial pistachio orchards showing disease symptoms were surveyed between 2017 and 2018. Botryosphaeriaceae fungi were consistently isolated from affected shoots, among other fungal families with minor relevance. Representative isolates of each family were characterized based on colony and conidial morphology, optimum growth temperature, and the comparison of DNA sequence data (ITS, LSU, EF, TUB2, and ACT genomic regions). Detached and attached shoots, and attached panicles of pistachio cv. Kerman were inoculated with mycelial plugs or conidial suspensions to demonstrate the pathogenicity of the selected isolates. Botryosphaeria dothidea, Lasiodiplodia pseudotheobromae, Neofusicoccum mediterraneum, N. parvum, Diaporthe neotheicola, Diaporthe sp., Eutypa lata, Eutypa sp., Cytospora sp., and Phaeoacremonium minimum were identified. P. minimum had the highest optimum growth temperature (29.6 °C) and Cytospora sp. the lowest (21–22 °C). Botryosphaeriaceae isolates showed the largest lesions on inoculated shoots, with L. pseudotheobromae being the most aggressive, followed by Neofusicoccum species. Panicles inoculated with N. mediterraneum showed blight symptoms and canker formation 6 weeks after inoculation, without significant differences in aggressiveness between isolates. This work reports relevant information about this emerging disease in the novel Spanish pistachio‐growing areas.

Grapevine Trunk Diseases Management in Vineyards from Central Transylvania

Grapevine trunk diseases (GTD) are among the most important diseases reported in vineyards in central Transylvania. On average, up to 5% of the vineyards are affected by the GTD although there are also vineyards where the incidence of the attack exceeds 15%. Recent studies show that the importance of pathogens in wood is so great that they are considered limiting factors that affect the stability of the world’s vineyards. The main objective of this study is to develop new sustainable management alternatives for the GTD control. For this purpose, an agroecological variant including prophylactic and cultural measures and two treatments with biofungicides based on: Trichoderma atroviride strain 8, Trichoderma atroviride strain B11 and Trichoderma harzianum, were tested. The frequency of the attack of the main four GTD diseases (Esca complex, Phomopsis dieback, Eutypa dieback and Crown gall) on the SCDVV Blaj homologated grapevine varieties, ‘Astra’, ‘Amurg’, ‘Brumariu’, ‘Blasius’ ‘Radames’, ‘Rubin’ and ‘Selena’, was assessed showing that these had a lower frequency of the symptoms compared with the widely cultivated variety ‘Feteasca regala’. Also the effect of training system (Classical versus semi-high Guyot) on GTD is presented. The classical system had decreased the frequency of crown gall and Phomopsis dieback, and the semi-high Guyot system had decreased Eutypa dieback’s frequency, indicating that the training system is an important tool of the agroecological system in maintaing the health of grapevine. Biofungicides tested help reduce the symptoms of GTD, but not enough to help reduce the premature death of grapevine.

Screening of some plant pathogenic fungi for the presence of dsRNA mycoviruses

Mycoviruses can infect many fungi and some may cause hypovirulence, which is a common phenomenon used in the biological control of certain fungal diseases of the plants. The most successful example regarding the use of mycoviruses and hypovirulent strains in biological control is the chestnut blight. In this study, the isolates of fungi, namely Phomopsis viticola from grapevine, Verticillium dahliae from cotton and olive, Rhizoctonia solani from cotton and Leucostoma spp., from cherry were screened for the presence of dsRNA mycoviruses. Isolation of dsRNAs was performed and dsRNA bands were analyzed by agarose gel electrophoresis. Putative dsRNA bands were detected in eight of 80 P. viticola isolates from grapevine, one of 50 V. dahliae isolates from olive, three of 50 V. dahliae isolates from cotton, six of 50 R. solani isolates from cotton and three of 50 Leucostoma spp., isolates from cherry. The estimated molecular sizes of the dsRNAs ranged from approximately 12.0 to 20.0 kb.

Diversity Profiling of Grapevine Microbial Endosphere and Antagonistic Potential of Endophytic Pseudomonas Against Grapevine Trunk Diseases.

Grapevine trunk diseases (GTDs) are a serious problem of grapevines worldwide. The microbiota of the grapevine endosphere comprises prokaryotic and eukaryotic endophytes, which may form varied relationships with the host plant from symbiotic to pathogenic. To explore the interaction between grapevine endophytic bacteria and GTDs, the endomicrobiome associated with grapevine wood was characterized using next-generation Illumina sequencing. Wood samples were collected from grapevine trunks with and without external symptoms of GTD (cankers) from two vineyards in the Hunter Valley and Hilltops, NSW, Australia and metagenomic characterization of the endophytic community was conducted using the 16S rRNA gene (341F/806R) and ITS (1F/2R) sequences. Among the important GTD pathogens, Phaeomoniella, Phaeoacremonium, Diplodia and Cryptovalsa species were found to be abundant in both symptomatic and asymptomatic grapevines from both vineyards. Eutypa lata and Neofusicoccum parvum, two important GTD pathogens, were detected in low numbers in Hilltops and the Hunter Valley, respectively. Interestingly, Pseudomonas dominated the bacterial community in canker-free grapevine tissues in both locations, comprising 56–74% of the total bacterial population. In contrast, the Pseudomonas population in grapevines with cankers was significantly lower, representing 29 and 2% of the bacterial community in Hilltops and the Hunter Valley, respectively. The presence of Pseudomonas in healthy grapevine tissues indicates its ability to colonize and survive in the grapevine. The potential of Pseudomonas spp. as biocontrol agents against GTD pathogens was also explored. Dual culture tests with isolated fluorescent Pseudomonas against mycelial discs of nine Botryosphaeria dieback, three Eutypa dieback, and two Esca/Petri disease pathogens, revealed antagonistic activity for 10 Pseudomonas strains. These results suggest the potential of Pseudomonas species from grapevine wood to be used as biocontrol agents to manage certain GTD pathogens.

Hunting modulators of plant defence: the grapevine trunk disease fungus Eutypa lata secretes an amplifier for plant basal immunity.

Grapevine trunk diseases (GTDs) are progressively affecting vineyard longevity and productivity worldwide. To be able to understand and combat these diseases, we need a different concept of the signals exchanged between the grapevine and fungi than the well-studied pathogen-associated molecular pattern and effector concepts. We screened extracts from fungi associated with GTDs for their association with basal defence responses in suspension cells of grapevine. By activity-guided fractionation of the two selected extracts, O-methylmellein was identified as a candidate modulator of grapevine immunity. O-Methylmellein could not induce immune responses by itself (i.e. does not act as an elicitor), but could amplify some of the defence responses triggered by the bacterial elicitor flg22, such as the induction level of defence genes and actin remodelling. These findings show that Eutypa lata, exemplarily selected as an endophytic fungus linked with GTDs, can secrete compounds that act as amplifiers of basal immunity. Thus, in addition to elicitors that can trigger basal immunity, and effectors that down-modulate antibacterial basal immunity, once it had been activated, E. lata seems to secrete a third type of chemical signal that amplifies basal immunity and may play a role in the context of consortia of mutually competing microorganisms.

Pathogenic fungi isolated in association with grapevine trunk diseases in New Zealand

ABSTRACTGrapevine trunk diseases (GTDs), caused by a complex of fungi, are a global threat to vineyard longevity. Identifying the fungi in each growing region is crucial for interpreting symptoms and understanding disease progression. Despite considerable research, the spectrum of fungi involved in GTDs in New Zealand remains uncertain and species identities within key taxonomic groups require validation with molecular sequences. We provide a synopsis of fungi from known pathogenic GTD taxa that have been identified in culture-dependent studies in New Zealand, especially those accessible through culture collections such as the International Collection of Microorganisms from Plants (ICMP). Results from a 2007–2010 countrywide vineyard survey for GTD fungi are presented, plus new isolates and associated DNA sequences from a 2017 survey of Marlborough and Hawke’s Bay vineyards and from institutional microbial collections. These new records clarify that authentic Eutypa lata and Phaeomoniella chlamydospora fungi, which are widely studied GTD pathogens, are present and probably common in New Zealand. First records of Inonotus, Diatrype, Sporocadus and Phaeoacremonium species are presented from New Zealand vineyards. The DNA sequences presented from GTD pathogens will facilitate the use of molecular detection technologies for measuring pathogen distributions in New Zealand vineyards and for biosecurity detections.