Eutypa Dieback Of Grapevines Research Articles

A Field Survey of Grapevine Germplasm Susceptible to Eutypa Dieback

Eutypa dieback of grapevine is a trunk disease that impacts vineyard productivity worldwide. Grape germplasm is typically evaluated for resistance to Eutypa dieback through controlled inoculations in the greenhouse, although the high level of replication required of this approach (40 plants per genotype) can limit the total number of genotypes evaluated. An alternative approach is to evaluate naturally infected genotypes in the field. We rated the incidence and severity of vines with the diagnostic leaf symptoms of Eutypa dieback and the incidence of mortality among such vines of 973 Vitis vinifera accessions (planted in duplicate) at the US Department of Agriculture, National Clonal Germplasm Repository in Davis, CA, USA, which is maintained as a living collection for grape research. Across 3 years and spanning a total of 5 years (2011, 2013, and 2015), 120 accessions had leaf symptoms in one or more years (“susceptible accessions”). Courbu blanc [Davis Vitis identification tag (DVIT) 2313], Frankenthal blanc (DVIT 2115), and Pinot gris (DVIT 0907) were the only accessions with leaf symptoms each year. Accessions with the most severe leaf symptoms (a rating of 5 points) were Chasselas Napoleon (DVIT 0375) and Queen of the Vineyard (DVIT 0496). We identified susceptible accessions—namely, those related to ‘Chasselas’ and ‘Muscat’—with a shared genetic background, based on a previous single nucleotide polymorphism genotyping effort of the collection. Especially for grapevine, a long-lived perennial that is meant to produce a crop for decades, knowledge of susceptible accessions and their pedigrees can help inform breeding programs and studies on the host response to infection.

Phenotyping grapevine cultivars for resistance to Eutypa dieback

Eutypa dieback of grapevine is a trunk disease that affects vineyard productivity. Wood symptoms of this disease develop consistently in greenhouse-grown plants, after inoculation of woody stems with the causal fungus Eutypa lata. Wood symptoms are a common measure of host cultivar resistance and E. lata isolate virulence. Leaf symptoms of the disease also develop in the greenhouse, although reports of low correlations between severity of wood and leaf symptoms (for some cultivars and isolates) indicate that a definitive procedure is required for evaluating cultivar resistance. Three ‘phenotyping assays’, replicated with two E. lata isolates (BX1-10 and M14), were assessed for quantifying resistance of a set of Vitis vinifera cultivars (‘Black Corinth’, ‘Carignane’, ‘Husseine’, ‘Merlot’, ‘Muscat Hamburg’, ‘Palomino’, ‘Peloursin’, ‘Primitivo’, and ‘Thompson Seedless’). The methods were: Assay 1 (leaf and woody-stem symptoms measured 1 year post-inoculation on plants propagated from rooted, dormant cuttings); Assay 2 (green stem symptoms measured 4 months post-inoculation on plants propagated from rooted, green cuttings); and Assay 3 (leaf symptoms measured 6 weeks post-inoculation on plants propagated from rooted, dormant cuttings). High rates of mortality among some cultivars (‘Merlot’) in Assay 3 confounded results based on leaf symptoms. Results from Assays 1 and 2 were more consistent with each other, especially for the most resistant cultivars [‘Merlot’ and ‘Primitivo’ (aka ‘Zinfandel’)]’, than they were for these cultivars in Assay 3. Compared to resistant cultivars, there was more variation in the most susceptible cultivar, including ‘Black Corinth’, ‘Carignane’, ‘Husseine’, and ‘Thompson Seedless’, regardless of the assay. Assay 1 with isolate BX1-10 was the most repeatable and provided data on wood and leaf symptoms for cultivar comparisons. Assay 2 was the most rapid, and gave results similar to those from Assay 1. Assay 2 also accommodated germplasm that can only be propagated from green cuttings.

Molecular detection and identification of Diatrypaceous airborne spores in Australian vineyards revealed high species diversity between regions.

The grapevine trunk disease, Eutypa dieback (ED), causes significant vine decline and yield reduction. For many years, the fungus Eutypa lata was considered the main pathogen causing ED of grapevines in Australia. Recent studies showed other Diatrypaceous fungi were also associated with vines exhibiting dieback symptoms but there is limited information on how these fungal pathogens spread in vineyards. Thus, information on the spore dispersal patterns of Diatrypaceous fungi in different wine regions will assist in identifying high-risk infection periods in vineyards. Using more than 6800 DNA samples from airborne spores collected from eight wine regions in south-eastern Australia over 8 years using a Burkard spore trap, this study investigated the diversity and abundance of Diatrypaceous species, using multi-faceted molecular tools. A multi-target quantitative PCR (qPCR) assay successfully detected and quantified Diatrypaceous spores from 30% of the total samples with spore numbers and frequency of detection varying between regions and years. The high-resolution melting analysis (HRMA) coupled with DNA sequencing identified seven species, with E. lata being present in seven regions and the most prevalent species in the Adelaide Hills, Barossa Valley and McLaren Vale. Cryptovalsa ampelina and Diatrype stigma were the predominant species in the Clare Valley and Coonawarra, respectively while Eutypella citricola and Eu. microtheca dominated in the Hunter Valley and the Riverina regions. This study represents the first report of D. stigma and Cryptosphaeria multicontinentalis in Australian vineyards. This study further showed rainfall as a primary factor that triggers spore release, however, other weather factors that may influence the spore release in different climatic regions of Australia still requires further investigation.

Population genomics of the grapevine pathogen Eutypa lata reveals evidence for population expansion and intraspecific differences in secondary metabolite gene clusters.

Eutypa dieback of grapevine is an important disease caused by the generalist Ascomycete fungus Eutypa lata. Despite the relevance of this species to the global wine industry, its genomic diversity remains unknown, with only a single publicly available genome assembly. Whole-genome sequencing and comparative genomics was performed on forty Australian E. lata isolates to understand the genome evolution, adaptation, population size and structure of these isolates. Phylogenetic and linkage disequilibrium decay analyses provided evidence of extensive gene flow through sexual recombination between isolates obtained from different geographic locations and hosts. Investigation of the genetic diversity of these isolates suggested rapid population expansion, likely as a consequence of the recent growth of the Australian wine industry. Genomic regions affected by selective sweeps were shown to be enriched for genes associated with secondary metabolite clusters and included genes encoding proteins with a role in nutrient acquisition, degradation of host cell wall and metal and drug resistance, suggesting recent adaptation to both abiotic factors and potentially host genotypes. Genome synteny analysis using long-read genome assemblies showed significant intraspecific genomic plasticity with extensive chromosomal rearrangements impacting the secondary metabolite production potential of this species. Finally, k-mer based GWAS analysis identified a potential locus associated with mycelia recovery in canes of Vitis vinifera that will require further investigations.

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

Identification of Eutypa spp. Causing Eutypa Dieback of Grapevine in Eastern North America.

Eutypa dieback of grapevine is caused by Eutypa lata in production areas with Mediterranean climates in California, Australasia, Europe, and South Africa. Eutypa dieback has also been described in the colder, eastern North American vineyards where cultivars adapted from native Vitis spp. (e.g., Vitis × labruscana 'Concord') are primarily grown. However, the causal agents associated with the diseases in this region have not been conclusively identified. Examination of 48 vineyards showing symptoms of dieback in the northeastern United States (Connecticut, Massachusetts, Michigan, New York, Ohio, and Rhode Island) and Ontario, Canada revealed that vineyards were mainly infected by Eutypa spp. other than E. lata. Multigene phylogenies (internal transcribed spacer ribosomal DNA, β-tubulin, and RNA polymerase II) of isolates recovered from these vineyards indicated that Eutypa dieback is caused primarily by an undescribed Eutypa sp. and E. laevata. Eutypa sp. was recovered from 56% of the vineyards examined, whereas E. laevata and E. lata were less far common (17 and 6%, respectively). Fruiting body morphology and spore dimensions supported phylogenetic separation of the three taxa. Pathogenicity tests conducted on Vitis vinifera 'Chardonnay' in the greenhouse and in the field verified that all three species were able to cause wood canker and to infect pruning wounds, respectively.

Draft Genome Sequence of the Grapevine Dieback Fungus Eutypa lata UCR-EL1.

The vascular pathogen Eutypa lata, which causes Eutypa dieback in grapevines, is a major threat to grape production worldwide. Here, we present the first draft genome sequence of E. lata (UCR-EL1). The computational prediction and annotation of the protein-coding genes of UCR-EL1 provide an initial inventory of its potential virulence factors.

Control of Eutypa dieback in grapevines using remedial surgery

A series of long-term trials was established to monitor the effect of remedial surgery for the control of Eutypa dieback in commercial vineyards of South Australia. Removing infected cordons and trunks has been used as a strategy for managing Eutypa dieback in grapevines for many years and this study is the first to provide evidence of its effect in controlling the disease. Between 42 and 100% of vines produced watershoots after removal of infected wood, depending on time after surgery and height of the trunk remaining. Remedial surgery reduced the incidence of vines with foliar symptoms of Eutypa dieback in vineyards, and the severity of those symptoms, but the efficacy varied with the presumed extent of pre-existing infection and the origin of the watershoot. It is recommended that all stained wood and a further 10 cm of healthy tissue be removed to reduce the likelihood that symptoms of Eutypa dieback will recur.

Studies on the effect of water and temperature stress on grapevines inoculated with Eutypa lata

Three independent studies were conducted in Australia and Spain to examine the effect of water and temperature stress on the development of Eutypa dieback of grapevines. In Adelaide, South Australia, ‘Red Grenache’ vines in pots were inoculated with Eutypa lata and subjected to various temperature and soil water regimes, then assessed for foliar symptoms, wood staining and colonization by the fungus. Vines subjected to a combination of heat or cold plus low or high soil moisture displayed more severe foliar symptoms, the most severe occurring on vines subjected to the hottest (30°C) and wettest (20–40 % soil water content) conditions. Wood staining was not related to foliar symptom severity or to the temperature and moisture combination. Furthermore, there was no relationship between staining and mycelial growth, indicating that staining may not be an accurate reflection of the spread of E. lata . In Cabrils, Spain, ‘Tempranillo’ vines were subjected to water stress in pots and showed a significant reduction in shoot diameter growth, stomatal conductance and leaf water potential. Inoculation with E. lata also decreased the leaf water potential of stressed vines. Wood staining in inoculated vines was similar irrespective of watering treatment. Further investigations are needed to elucidate the relationship between stress and growth of E. lata in infected vines. Field experiments in two climatically different regions (Barossa Valley and Riverland) of South Australia suggested that water-stressed vines in a warm, dry environment may be more susceptible to infection of pruning wounds by E. lata than vines receiving standard watering.

Genetic structure of the fungal grapevine pathogen Eutypa lata from four continents

The generalist ascomycete fungus Eutypa lata causes Eutypa dieback of grapevine (Vitis vinifera) worldwide. To decipher the cosmopolitan distribution of this fungus, the population genetic structure of 17 geographic samples was investigated from four continental regions (Australia, California, Europe and South Africa), based on analysis of 293 isolates genotyped with nine microsatellite markers. High levels of haplotypic richness (R = 0·91–1) and absence of multilocus linkage disequilibrium among loci supported the preponderance of sexual reproduction in all regions examined. Nonetheless, the identification of identical multilocus haplotypes with identical vegetative compatibility groups, in some vineyards in California and South Africa, suggests that asexual dispersal of the fungus among neighbouring plants could be a rare means of disease spread. The greatest levels of allelic richness (A = 4·89–4·97) and gene diversity (H = 0·66–0·69) were found in Europe among geographic samples from coastal areas surrounding the Mediterranean Sea, whereas the lowest genetic diversity was found in South Africa and Australia (A = 2·78–3·74; H = 0·49–0·57). Samples from California, Australia and South Africa, which had lower genetic diversity than those of Europe, were also characterized by demographic disequilibrium and, thus, may represent founding populations of the pathogen. Low but significant levels of genetic differentiation among all samples (DEST = 0·12, P = 0·001; FST = 0·03, P = 0·001) are consistent with historical gene flow preventing differentiation at continental scales. These findings suggest that global, human‐mediated spread of the fungus may have resulted in its current global distribution.

Host Range, Biological Variation, and Phylogenetic Diversity ofEutypa latain California

The objectives of this study were to investigate the host range of Eutypa lata in the major grape-growing regions in California and to analyze the phenotypic variation and phylogenetic diversity of E. lata isolates. Perithecia of E. lata were found on grapevines, in apricot, almond, cherry, apple, and pear tree orchards, and on ornamentals (oleander) and native plant species (California buckeye, big leaf maple, and willow). Multigene phylogenies of ribosomal DNA internal transcribed spacer, β-tubulin, and RPB2 genes confirmed the identity of E. lata recovered from the various host plants but also revealed sequence differences among isolates. The intraspecific phylogenetic diversity of E. lata did not correspond to geography or source of isolation, and intraspecific groups were not consistent across the different DNA phylogenies. Significant phenotypic variation also was detected among E. lata isolates, including ascospore and conidium length as well as level of aggressiveness on grapevines. Pathogenicity studies proved that all isolates were infectious to grapevine, suggesting that the native vegetation surrounding vineyards can serve as inoculum sources that may constitute an important element in the epidemiology of Eutypa dieback in grapevines.

Protection of grapevine pruning wounds from infection byEutypa lata

Background and Aims: Eutypa dieback is a major threat to the sustainability and productivity of the viticulture industry worldwide. The fungicide benomyl has been the most effective treatment to protect wounds against infection by ascospores of Eutypa lata and to control eutypa dieback. However, because of the withdrawal of benomyl from the market, there is a need to develop alternatives to protect pruning wounds. Methods and Results: Twenty-five compounds were evaluated in laboratory experiments and field trials. A selection of the compounds effective at inhibiting germination and/or mycelial growth in the laboratory were further evaluated in the field. Of the 15 fungicides tested, carbendazim was the most effective in reducing colonisation of pruning wounds by E. lata in the field. Other fungicides, including fluazinam, pyrimethanil and pyraclostrobin, reduced colonisation of wounds by E. lata but require further evaluation at higher concentrations. Physical barriers such as acrylic paint (with or without fungicides) and a commercial tree wound paste formulated with fungicides (Garrison) also protected pruning wounds from infection by E. lata. Conclusions: Fungicides and physical barriers have been identified for the control of eutypa dieback in grapevines. The registration of Bavistin (carbendazim) and Garrison is being sought for use on pruning wounds on grapevines in Australia. Significance of the Study: Protection of pruning wounds is essential for the management of eutypa dieback in grapevines. Identification of alternative methods for disease control will provide significant economic benefits for the grapegrowing industry.

The Influence of Climate on Foliar Symptoms of Eutypa Dieback in Grapevines

ABSTRACT Foliar symptoms of Eutypa dieback, caused by Eutypa lata, in grapevines, cv. Shiraz, varied from year to year in a 6-year study conducted in South Australia and, although trends were similar for vineyards within geographical regions, differences were observed between regions. We attempted to elucidate the causes underlying this variation and hypothesized that it was influenced by climatic factors. A number of possible relationships were identified between climate and symptom expression: (i) increased symptom expression was related to increased winter rainfall 18 months earlier, (ii) decreased disease incidence and prevalence were related to increased temperature in spring, and (iii) a reduction in disease incidence was related to both very high and very low rainfall in October. Theories for these relationships are proposed and require further investigation. A conceptual model was developed which requires validation and has the potential to predict the incidence of foliar symptoms of Eutypa dieback. Information from this study could lead to an improved integrated pest management system to suppress foliar symptoms and sustain productivity of vines infected with E. lata.

Genetic variation in Australian isolates of the grapevine pathogenEutypa lata

Eutypa lata is an ascomycete fungus that causes eutypa dieback of grapevines, a disease which threatens vine productivity and longevity throughout the world. We assessed genetic variation among 35 isolates received as E. lata from Australia, Europe, California and South Africa using restriction fragment length polymorphism analysis. A subset of 10 isolates previously analysed for secondary metabolite production was also analysed using randomly amplified polymorphic DNA markers. Molecular analyses showed a high level of genetic diversity, with each isolate having a unique haplotype. Phylogenetic analysis did not allow separation of isolates based on geographic location or host species from which isolateswere obtained. Therewas no apparent correlation betweenDNAprofile and secondary metabolite production by E. lata. The results of this study showed a degree of genetic diversity similar to that reported for European and North American populations of E. lata, and are consistent with the hypothesis that the sole means of dispersal of the pathogen is by ascospores.

Secondary metabolite production by the fungal pathogen Eutypa lata: Analysis of extracts from grapevine cultures and detection of those metabolites in planta

Eutypa dieback of grapevines is caused by the fungal pathogen Eutypa lata and reduces vineyard longevity worldwide. Early detection could reduce losses due to this disease, so our aim was to identify acetylenic phenol metabolites of E. lata that could prove suitable as chemical markers in an early diagnostic test for the pathogen. Accordingly, secondary metabolite production by 30 isolates of E. lata grown on media derived from canes of three grapevine cultivars was analysed using HPLC. Six metabolites, namely eutypinol, methyl eutypinol, eulatachromene, eutypine, 2-iso-propenyl-5-formylbenzofuran and eulatinol, were detected in culture filtrates. Most abundant were eutypinol and methyl eutypinol, produced by 97 and 83% of isolates, respectively. There was no apparent correlation between secondary metabolite production on media containing milled canes from the three cultivars of grapevine, and the field tolerance of these same cultivars to Eutypa dieback. When various other fungi commonly isolated from grapevine trunks in Australia were grown on milled cane, no secondary metabolites characteristic of E. lata were detected, suggesting such compounds are specific to E. lata. To examine the detection of secondary metabolites in planta, micropropagated grapevine plantlets were treated with purified or crude culture filtrates from nine isolates of E. lata grown on malt yeast broth. Various secondary metabolites were identified in treated plantlets, however, no single compound was detected consistently. Eutypinol was detected in micropropagated grapevine plantlets inoculated with mycelium of E. lata, however, no metabolites were detected in the sap of vines which had been artificially inoculated with the pathogen.

Phenolic and heterocyclic metabolite profiles of the grapevine pathogen Eutypa lata

The ascomycete Eutypa lata is the causative agent of eutypa dieback in grapevines, a serious economic problem in major wine grape producing areas. In order to develop a predictive, non-destructive assay for early detection of fungal infection, the phenolic metabolite profiles of 11 strains of E. lata grown on four different artificial growth media were analyzed by HPLC and their variability compared with growth on Cabernet Sauvignon grapevine wood and wood extracts. Six compounds were generally produced in significant amounts, namely eutypinol, eulatachromene, and eutypine and its benzofuran cyclization product, together with siccayne and eulatinol. The two most widely distributed and abundant metabolites were eutypinol and eulatachromene, which were present in 8 of the strains grown on grapewood aqueous extract fortified with sucrose. Metabolite production on grapevine extract was greatly enhanced relative to the artificial media, indicating that this native substrate provides optimal conditions and a more representative profile of the metabolites produced in the natural disease state. The primary metabolites were tested in a grapeleaf disc bioassay to establish their relative toxicity. Neither eutypinol nor siccayne were phytotoxic; eulatachromene, eulatinol, eutypine, and the benzofuran exhibited necrotic effects in the bioassay. The results indicate that eutypa dieback may be caused by several E. lata metabolites rather than a single compound.

Eutypa dieback in grapevines: differential production of acetylenic phenol metabolites by strains of Eutypa lata.

The production of acetylenic phenol metabolites in vitro by three strains of the ascomycete Eutypa lata, the causative agent of dying-arm disease in grapevines, has been investigated. Metabolite composition and yields differed significantly between strains and with growth medium but usually reached a maximum after 24-30 days of fungal growth. A general method for the analysis and identification of metabolites by gas chromatography/mass spectrometry of their trimethylsilyl ether derivatives was developed and individual compounds were quantitated by analytical high-performance liquid chromatography (HPLC) and separated by preparative HPLC. The phenolic aldehyde, eutypine (1), reported to be the grape phytotoxin, occurred in only one of the strains examined whereas the primary metabolite was the corresponding alcohol, eutypinol (2), the presumptive detoxification product. A novel metabolite was isolated as a major constituent, together with a minor component, and their structures were established by spectroscopic methods as a methoxyquinol, named eulatinol (4), and a chromene analog (9) of 2, respectively. The evidence suggests that 1 is not solely responsible for phytotoxicity in grapevines but that dying-arm disease may result from a suite of compounds elaborated by the fungus, with the composition dependent on fungal strain and nutritional source.

Eutypa Dieback of Grapevine and Apricot

Eutypa dieback, whose primary economic hosts are Vitis L. spp. (grapevine) and Prunus armeniaca L. (apricot), is caused by the following pathogen: Eutypa lata (Pers:Fr.) Tul. & C. Tul. (=Eutypa armeniacae Hansf. & Carter); its anamorph is Libertella blepharis A.L. Sm. (=Cytosporina Sacc. sp.). This article covers taxonomy, symptoms and signs on grapevine and apricot, host range, geographical distribution, isolation, identification, storage, and pathogenicity tests. Accepted for publication 13 February 2001. Published 19 February 2001.

Application of the logistic-normal-binomial distribution to the analysis of Eutypa dieback disease incidence

The analysis of disease incidence data when diseased plants are aggregated in clusters is discussed. The logistic-normalbinomial distribution provides a basis both for analysing experiments according to their factor structure and for describing the observed frequency distribution of affected plants per sampling unit. These analyses are illustrated with data from disease assessments of Eutypa dieback of grapevine in Californian vineyards. A comparison of the results of this study with those of a previous one suggests that clustering of Eutypa dieback may occur on different scales, dependent on the presence ofperithecia ofthe causal organism, Eutypa lata, in a vineyard.

Reductions in Yield and Vegetative Growth of Grapevines Due to Eutypa Dieback

Eutypa dieback of grapevines is a serious canker disease that slowly kills vines, but there is little information on yield reduction of declining vines. The severity of Eutypa dieback on individual grapevines was assessed in 1991 and 1992 as the proportion of the vines'spurs killed or symptomatic. In each year, Eutypa dieback caused a significant reduction in yield of infected vines compared with healthy vines. The linear relationship between disease severity (d) and yield (y), expressed as a percentage of the yield of healthy vines, was y=101.0-90.26d (r 2 =0.70) in 1991, and y=100.1-98.81d (r 2 =0.79) in 1992. The slope of this relationship was not significantly different between years or among five vineyards of two cultivars (Chenin blanc and French Colombard) [...]