Eutypa Lata Research Articles

Modulation of Protein Phosphorylation, N-Glycosylation and Lys-Acetylation in Grape (Vitis vinifera) Mesocarp and Exocarp Owing to Lobesia botrana Infection

Grapevine (Vitis vinifera) is an economically important fruit crop that is subject to many types of insect and pathogen attack. To better elucidate the plant response to Lobesia botrana pathogen infection, we initiated a global comparative proteomic study monitoring steady-state protein expression as well as changes in N-glycosylation, phosphorylation, and Lys-acetylation in control and infected mesocarp and exocarp from V. vinifera cv Italia. A multi-parallel, large-scale proteomic approach employing iTRAQ labeling prior to three peptide enrichment techniques followed by tandem mass spectrometry led to the identification of a total of 3059 proteins, 1135 phosphorylation sites, 323 N-linked glycosylation sites and 138 Lys-acetylation sites. Of these, we could identify changes in abundance of 899 proteins. The occupancy of 110 phosphorylation sites, 10 N-glycosylation sites and 20 Lys-acetylation sites differentially changed during L. botrana infection. Sequence consensus analysis for phosphorylation sites showed eight significant motifs, two of which containing up-regulated phosphopeptides (X-G-S-X and S-X-X-D) and two containing down-regulated phosphopeptides (R-X-X-S and S-D-X-E) in response to pathogen infection. Topographical distribution of phosphorylation sites within primary sequences reveal preferential phosphorylation at both the N- and C termini, and a clear preference for C-terminal phosphorylation in response to pathogen infection suggesting induction of region-specific kinase(s). Lys-acetylation analysis confirmed the consensus X-K-Y-X motif previously detected in mammals and revealed the importance of this modification in plant defense. The importance of N-linked protein glycosylation in plant response to biotic stimulus was evident by an up-regulated glycopeptide belonging to the disease resistance response protein 206. This study represents a substantial step toward the understanding of protein and PTMs-mediated plant-pathogen interaction shedding light on the mechanisms underlying the grape infection.

Temporal Patterns of Sporulation Potential of Phomopsis viticola on Infected Grape Shoots, Canes, and Rachises.

Phomopsis cane and leaf spot on Vitis spp. (grape) is currently understood to be monocyclic, with primary inoculum only being produced early in the growing season. However, of the few published studies pertaining to sporulation of Phomopsis viticola, none specifically examined rachises, and none were designed to determine when infected tissues become capable of sporulation. The objective of these studies was to determine when grape shoots, canes, and rachises infected with P. viticola develop the capacity to sporulate, and to determine the time period during which those tissues remain capable of sporulation. Starting in 2009 and 2010, infected first-year shoots and rachises were collected biweekly throughout the growing season, into the dormant season, and into the following growing season. Tissues were collected from 'Catawba,' 'Concord,' and 'Reliance' vineyards. Samples were observed for sporulation after 48 h of incubation in a moist chamber at 23°C; the magnitude of the conidia production under these optimal conditions was considered the sporulation potential. For infections that occurred in 2009 and 2010, the production of conidia was not observed until after harvest. In the year following infection, sporulation potential was found from about bud break until shortly after the end of bloom. There was a generally consistent temporal pattern to relative sporulation potential across sampled vineyards, years, and grape tissues (rachises and canes), described by a modified β model, with peak sporulation potential occurring around 16 May. These results confirmed that Phomopsis cane and leaf spot is a monocyclic disease and support control recommendations for use of fungicides in spring.

Grapevine trunk diseases: complex and still poorly understood

This review presents an overview of eutypa dieback, esca and botryosphaeria dieback, the predominant grapevine trunk diseases worldwide. It covers their symptomatologies in the trunk, leaves and berries; the characteristics of the different fungal species associated with them; and host–pathogen interactions. Here, the host–pathogen relationship is defined at the cytological, physiological and molecular levels. Currently available experimental tools for studying these diseases, both in vitro and in the field, are discussed. Finally, a progress report on their control, which, since the ban of sodium arsenite, comprises chemical, biological and/or sanitation methods, is presented.

Identification and Characterization of Eutypa lata on Grapevine in Serbia.

In the period from late May 2004 to late May 2010, grapevine (Vitis vinifera L.) between 11 and 22 years old was observed for the incidence of symptoms of shortened shoots and zigzag internodes, with tiny, chlorotic leaves, torn and bended edges, with necrosis along the edges of leaves and dead internervous tissue. These symptoms are conspicuous especially when the vine is in the F phases of development. Later, in the course of vegetation, the dying of infected shoots and branches or covering of symptoms by a new foliage mass is perceived. Foliar symptoms are initially confined to one arm of infected vines; however, as the disease progresses, symptoms may spread throughout the entire vine. If a cross-section is made of an infected trunk, the canker appears as a wedge-shaped area of discolored wood spreading to the center of the trunk. In the period from 2004 to 2010, disease incidence was high, approaching 20%, and decline-affected cordons, vine branches, or whole plants was very high, resulting in losses of more than 35%. The loss created by a decline in grapevine quality is not included in this estimate. In this study, the causal agent was diagnosed as Eutypa lata (anamorph Libertella blepharis), on the basis of morphology of conidia of a Libertella anamorph on a 4- to 6-week-old culture on PDA (1) and by molecular identification. Molecular identification was performed by PCR and RFLP analysis and supplemented by sequence analysis. Total DNA was isolated from cultured mycelia of fungi using CTAB extraction protocol. PCR reaction was performed by universal ITS1/ITS4; the primer pair and RFLP patterns were determined after restriction with AluI (3). For specific identification of E. lata, the primer pair Lata 1/Lata 2.2 (2) were used and the 385-bp fragment was detected from analyzed isolates. Five selected isolates were purified and a fragment encompassing ITS1, ITS2, and 5.8S rDNA gene was sequenced. Sequences were deposited in the NCBI database under Accession Nos. JQ041699, JQ041700, JQ041701, JQ041702, and JQ041703. Sequence comparisons revealed high nucleotide identity among isolates (99.6 to 100%). When aligned with other E. lata isolates retrieved from the NCBI database, Serbian isolates show the highest nucleotide identity with the isolates from North America (AY462541, AY462540, AY662393, AY662392) and Australia (EU835166, EU835163, EU835162, EU835161, EU835160, EU835159, EU835156). A pathogenicity test was performed in February 2006 in a greenhouse at room temperature (approximately 22°C) and included inoculation rooted cuttings of grapevine (cultivars Cabernet Sauvignon, Prokupac, and Drenak) plants by mycelium. Agar plugs containing mycelium were inserted into 5 mm diameter holes drilled in the main stem of the rootlings and sealed by wrapping with Parafilm. Uninoculated control vines treated with a sterile agar plug were included in the experiment. Foliar symptoms and discoloring of wood beneath and above the inoculation site, inoculated plants, was observed. Reisolation and reinoculation were performed 27 months later, and 54 months later the pathogenicity test was confirmed (4). To our knowledge, this is the first report of death of infected cordons of grapevine by E. lata in Serbia.

Calosphaeria Canker of Sweet Cherry Caused by Calosphaeria pulchella in California and South Australia.

California is the second largest sweet cherry producer in the United States with annual revenues up to $200 million. The South Australian cherry industry generates about 10% of Australia's overall production with approximately 1,500 metric tons of cherries produced yearly. In California, perennial canker diseases and subsequent branch dieback are responsible for extensive damage throughout sweet cherry orchards, reducing annual yields and tree longevity. Surveys of cherry orchards and isolation work were conducted in California to identify the main canker-causing agents. Calosphaeria pulchella was the main fungus isolated from cankers, followed by Eutypa lata and Leucostoma persoonii, respectively. Preliminary surveys in cherry orchards in South Australia documented C. pulchella and L. persoonii in cankers. The pathogenicity of C. pulchella in sweet cherry was confirmed following field inoculations of 2- to 3-year-old branches. C. pulchella was able to infect healthy wood and produce cankers with as much virulence as E. lata or L. persoonii. Spore trapping studies were conducted in two sweet cherry orchards in California to investigate the seasonal abundance of C. pulchella spores. Experiments showed that rain and sprinkler irrigation were important factors for aerial dissemination. Finally, this study illustrates the symptoms and signs of the new disease Calosphaeria canker.

Diagnosis of Eutypa lata infection in grapevines by serological detection of secreted polypeptides

Eutypa lata is the causal agent of a devastating disease affecting grapevines around the world. We have previously reported that the fungus secretes in its culture medium a variety of polypeptides, and we have developed serological method of detecting these. Rabbit antibodies raised against the polypeptide fraction, recognized secreted fungal proteins with high sensitivity (commonly 1 ng). These antibodies were specific since they cross-reacted with polypeptides secreted by various strains of Eutypa lata but not by other fungal pathogens involved in other wood decay diseases, namely esca (Phaeomoniella chlamydospora and Phaeoacremonium aleophilum) and black dead arm (Diplodia seriata and Neofusicoccum parvum). These results were obtained by ELISA assay and immunolocalization on ultrathin sections. The ability of the polypeptides to be transported in vines permitted development of a reliable dot-blot method of diagnosis rapid, easy to perform and not destructive for grapevines. Advantages and drawbacks of the method are discussed.`

CONTROL OF DIEBACK, CAUSED BY EUTYPA LATA, IN RED CURRANT (RIBES RUBRUM) AND GOOSEBERRY (RIBES UVA-CRISPA) IN THE NETHERLANDS

Over decades, growers in the Netherlands have problems with a disease that causes dying branches and stem cankers in red currant. For many years it was assumed that this disease was related to fungi such as Nectria cinnabarina, Phomopsis spp. and the insect Synanthedon tipuliformis. However, recently it was found by Applied Plant Research and the Plant Protection Service that the causal organism is the fungus Eutypa lata. The disease is considered of major economic importance, especially as red currant growing is rapidly expanding in the Netherlands. E. lata was identified with three detection methods (visual, plating and DNA). Symptoms of E. lata do not usually appear until currant plants are at least three to four years old. These cankers are always associated with old pruning wounds. Eventually, the entire branch is killed. High disease incidences and annual losses of 10% to 30% of the productive branches are reported. In some cases entire fields have to be replanted. E. lata is well known as one of the most destructive diseases of grapevines (Vitis vinifera). The importance of this disease in currant growing was not known. Research is focusing on the evaluation of control measures; e.g. chemical and biological control treatment of pruning wounds, and disease management such as sanitation practices. Also, the epidemiology of E. lata is studied. High densities of ascospores of E. lata were found in a spore trap placed in a red currant field in the Netherlands. In the subsequent field survey fruiting structures (stromata) and ascospores were found on dead infected red currant wood.

Fungal trunk pathogens associated with wood decay of almond trees on Mallorca (Spain).

Severe decline of almond trees has recently been observed in several orchards on the island of Mallorca (Balearic Islands, western Mediterranean Sea). However, the identity of the causal agents has not yet been investigated. Between August 2008 and June 2010, wood samples from branches of almond trees showing internal necroses and brown to black vascular streaking were collected in the Llevant region on the island of Mallorca. Several fungal species were subsequently isolated from the margin between healthy and symptomatic tissue. Five species of Botryosphaeriaceae (namely Botryosphaeria dothidea, Diplodia olivarum, D. seriata, Neofusicoccum australe and N. parvum), Eutypa lata, Phaeoacremonium iranianum and Phomopsis amygdali were identified based on morphology, culture characteristics and DNA sequence comparisons. Neofusicoccum parvum was the dominant species, followed by E. lata, D. olivarum and N. australe. First reports from almond include D. olivarum and Pm. iranianum. Two species are newly described, namely Collophora hispanica sp. nov. and Phaeoacremonium amygdalinum sp. nov.

The response to stress treatments of potted grapevines inoculated with <i>Eutypa lata</i> and <i>Botryosphaeria lutea</i> fungi associated with trunk disease

Current management options for grapevine trunk diseases are focused on ameliorating symptoms once they have occurred In grapevines and other crops plant stress has been observed to increase symptom expression for different pathogens depending on timing and type of stress This research aimed to establish whether stress to vines at the time of wounding enhances colonisation by fungi associated with trunk disease Potted plants were wounded and inoculated with two grapevine trunk fungi Eutypa lata and Botryosphaeria lutea Stress treatments (leaf removal and girdling) were applied to the vines immediately prior to inoculation Lesion size at the wound site and infection confirmed by reisolation of the pathogen were measured In these experiments stress did not induce greater infection incidence or larger lesions at the site of wounding Some difficulties in using potted plants to simulate responses of mature vines in the field are discussed

Effects of Temperature and Wetness Duration on the Sporulation of Phomopsis viticola on Infected Grape Canes

In 2008, research was initiated to examine effects of temperature and wetness duration on the sporulation of Phomopsis viticola on infected grape canes and to determine effects of interrupted wetness duration on sporulation. To determine effects of temperature (T) and wetness duration (WD) on sporulation, a split-plot experimental design was used, with T (5, 12, 15, 18, 20, 22, 25, 28, and 35°C) assigned to whole-plots and WD (11, 23, 35, 47, and 71 h) assigned to sub-plots. Linear and nonlinear mixed models were fitted to the data. Lower and upper limits of sporulation were found to be at 5 and 35°C, respectively. Optimum sporulation was near 22°C, and sporulation increased with increasing WD. Of the examined models, a generalized Analytis Beta model fit the data best. To determine effects of wetness interruption (IWD), a split-plot was used, with T (12, 15, and 20°C) assigned to whole-plots and IWD (0, 2, 4, 8, 12, and 24 h) assigned to sub-plots. Generally, sporulation declined with increasing IWD. An IWD of 12 h or more resulted in significantly and substantially less sporulation compared to the control (0 h IWD). Using a repeated-measures design, spore density and environmental data were measured in the vineyard during and following individual rain events; a preliminary model predicted the temporal trend in spore density within the vineyard fairly well (R2 = 0.719), although absolute magnitude of sporulation could not be predicted. Accepted for publication 27 April 2012. Published 23 July 2012.

Phytotoxins produced by fungi associated with grapevine trunk diseases.

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.

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.

Histo-pathology study of the growth of Trichoderma harzianum , Phaeomoniella chlamydospora and Eutypa lata on grapevine pruning wounds

Protecting grapevine pruning wounds by inoculating them with Trichoderma spp. can preventinfection from trunk disease pathogens. The growth and interactions of both, the biological control agent Trichoderma spp. and the vine pathogens, are not well understood. Green fluorescent protein (GFP)-labelled Trichoderma harzianum and red fluorescent protein (DsRed)-labelled T. harzianum , were dual-inoculatedwith Phaeomoniella chlamydospora (DsRed) or Eutypa lata (GFP) on fresh pruning wounds of one-year-oldCabernet Sauvignon and Sauvignon blanc shoots. The inoculated fungi were recovered from varying depthswithin the shoots at 30-day-intervals for 90 days. Trichoderma harzianum suppressed the pathogens and grew deeper in the presence of the pathogens than when it was singly inoculated; possibly an indication of pathogen recognition and competitive response. Eutypa lata was completely eliminated from Sauvignon blancin dual-inoculated canes after 90 days. The mycelium of P. chlamydospora (DsRed) grew extensively in thexylem vessels and possibly contributed to vessel occlusion. Phaeomoniella chlamydospora and E. lata caused blockage of the vessels and thickening of the vessel walls. Grapevine wood produced both tyloses and gums (gels) that blocked xylem vessels as a result of infection. A thickening of the cell walls of xylem fibres occurredonly in E. lata -inoculated shoots, indicative of a different mode of pathogenesis from P. chlamydospora .

Evaluation of biocontrol agents for grapevine pruning wound protection against trunk pathogen infection.

Trunk diseases of grapevine are caused by numerous pathogens, including Eutypa lata , Phaeomoniella chlamydospora , and species of Botryosphaeriaceae (incl. Botryosphaeria and aggregate genera), Phomopsis and Phaeoacremonium . Since infections occur mainly through pruning wounds, that have been shown by previous research to stay susceptible for up to 16 weeks after pruning, long-term pruning wound protection is required for prevention of infection. This study evaluated several biocontrol agents against a range of trunk disease pathogens in dual plate laboratory trials to determine macroscopic and microscopic interactions. The biocontrol agents had a substantial effect on all the pathogens, with a wide range of macroscopic and microscopic interactions observed. The best performing biocontrol agents were tested in two field trials. Fresh pruning wounds were treated with benomyl, Trichoderma products (Biotricho®, Vinevax® and ECO 77®) and isolates (USPP-T1 and -T2, identified as T. atroviride ) and Bacillus subtilis . Seven days after treatment the pruning wounds were inoculated by spraying with spore suspensions of Neofusicoccum australe , N. parvum , Diplodia seriata , Lasiodiplodia theobromae , Eutypa lata , Phaeomoniella chlamydospora or Phomopsis viticola . Eight months after inoculation, the treatments were evaluated by isolation onto potato dextrose agar. The efficacy of the biocontrol agents was in most cases similar or superior to that observed for benomyl. Isolate USPP-T1, in particular, was very effective, reducing incidence of Ph. viticola , E. lata , Pa. chlamydospora , N. australe , N. parvum , D. seriata and L. theobromae by 69, 76, 77, 78, 80, 85 and 92%, respectively. This is the first report of biological protection of grapevine pruning wounds against this group of grapevine trunk disease pathogens.

Temporal susceptibility of grapevine pruning wounds to trunk pathogen infection in South African grapevines.

Grapevine trunk diseases, caused by a range of phytopathogenic fungi, represent a serious impediment to wine and table grape production wherever these crops are cultivated. Previous studies have shown that the distribution of these pathogens is influenced by climate and that they are associated with a variety of internal wood decay symptoms. Little was known, however, about the influence of climate on the disease symptomatology of the different pathogens in a specific area. To address this, a survey was conducted in 30 wine and table grape vineyards in summer, marginal and winter rainfall regions of South Africa. Apart from Eutypa lata , which occurred only in the winter rainfall region, Phaeomoniella chlamydospora , species of Phaeoacremonium , Botryosphaeriaceae and Phomopsis occurred in all regions surveyed. The incidence of the fungal genera and species associated with trunk disease varied between regions, with overlapping symptom profiles that differed based on the climatic region. These findings suggest that symptom-based disease diagnosis alone is unreliable and that distribution and symptomatology of grapevine trunk pathogens are strongly influenced by climatic conditions in a specific production region.

Characterisation of the fungi associated with esca diseased grapevines in South Africa

During the period from 2001 to 2008, grapevines showing foliar and/or internal symptoms of esca were collected from various grape-growing regions in South Africa. Isolations were made from typical internal wood symptoms associated with esca, and fungal isolates were characterized by cultural growth patterns, morphology and phylogenetic inference. The gene regions sequenced included the internal transcribed spacers and the 5.8S rRNA gene (ITS) for the basidiomycetes and Phomopsis isolates , the partial b-tubulin and actin genes for Phaeoacremonium isolates and the partial translation elongation 1-a gene and the ITS for the Botryosphaeriaceae isolates. The fungi identified included Phaeomoniella chlamydospora and six species of Phaeoacremonium including Pm. aleophilum , Pm. alvesii , Pm. parasiticum , Pm.iranianum , Pm. mortoniae and Pm. sicilianum , of which the latter three are reported for the first time in South Africa. The following taxa were also identified: Eutypa lata , Phomopsis viticola , Phomopsis theicola , Diaporthe ambigua , Diplodia seriata , Neofusicoccum australe and N. parvum . The basidiomycete isolates were distributed over ten well supported monophyletic clades among genera of the Hymenochaetales. Two of these clades could be identified as species of Fomitiporia and Phellinus .

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.

Fungi associated with die-back symptoms of apple and pear trees, a possible inoculum source of grapevine trunk disease pathogens

A survey was undertaken on apple and pear trees in the main pome fruit growing areas ofthe Western Cape of South Africa to determine the aetiology of trunk diseases with specific reference to pathogens known to occur on grapevine, which are frequently cultivated in close proximity of these orchards. Several fungal genera containing known trunk disease pathogens were found. Two Diplodia species, D. seriata and Diplodia sp., were isolated along with Neofusicoccum australe and N. vitifusiforme . Four Phaeoacremonium species, Phaeoacremonium aleophilum , Pm. iranianum , Pm. mortoniae and Pm. viticola , two Phomopsis species linked to clades identified in former studies as Phomopsis theicola and Phomopsis sp. 7, and Eutypa lata were found. In addition, Paraconiothyrium brasiliense , Pr. variabile and a Pyrenochaeta like species were also isolated. Diplodia seriata (56% of total isolates) and Pm. aleophilum (22%) were most frequently isolate. First reports from pear wood include the Phaeoacremonium spp. and Paraconiothyrium brasiliense , while new reports from apple include Pm. aleophilum , Ph. theicola , Phomopsis sp. 7, Pr. variabile and E. lata . A pathogenicity trial was undertaken to determine the role of these species on apple, pear and grapevine shoots. Neofusicoccum australe caused the longest lesions on grapevine shoots, while Pr. variabile , D. seriata , Pm. mortoniae and the Pyrenochaeta -like sp. caused lesions that were longer than non-inoculatedand non-pathogen experimental controls. On pear shoots, Diplodia sp. and N. australe caused the longest lesions,followed by D. seriata and E. lata . On apple shoots, the longest lesions were caused by N. australe and Pm. iranianum . These results demonstrate that apple and pear trees in Western Cape orchards are hosts to many known trunk pathogens along with potential new trunk disease-causing fungi.

The distribution and symptomatology of grapevine trunk disease pathogens are influenced by climate

Grapevine trunk diseases, caused by a range of phytopathogenic fungi, represent a serious impediment to wine and table grape production wherever these crops are cultivated. Previous studies have shown that the distribution of these pathogens is influenced by climate and that they are associated with a variety of internal wood decay symptoms. Little was known, however, about the influence of climate on the disease symptomatology of the different pathogens in a specific area. To address this, a survey was conductedin 30 wine and table grape vineyards in summer, marginal and winter rainfall regions of South Africa. Apart from Eutypa lata , which occurred only in the winter rainfall region, Phaeomoniella chlamydospora , species of Phaeoacremonium , Botryosphaeriaceae and Phomopsis occurred in all regions surveyed. The incidence of the fungal genera and species associated with trunk disease varied between regions, with overlapping symptom profiles that differed based on the climatic region. These findings suggest that symptom-based disease diagnosis alone is unreliable and that distribution and symptomatology of grapevine trunk pathogens are strongly influenced by climatic conditions in a specific production region.

Efficacy of fungicides on mycelial growth of diatrypaceous fungi associated with grapevine trunk disease

Several species of Diatrypaceae have been recently isolated from the wood of cankered grapevines in several regions of the world and shown to be pathogenic with varying degrees of virulence when inoculated in stems of potted vines. Existing management strategies have focussed on the development of procedures and products to prevent or reduce Eutypa lata infection. The best method to prevent infection is by applying fungicides to wounds, but there are few registered chemicals for any of the diatrypaceous fungi in Australia. Six selected fungicides were evaluated in vitro for their efficacy in reducing mycelial growth of Eutypa lata, Cryptovalsa ampelina, Diatrypella vulgaris, Eutypa leptoplaca, Eutypella citricola and Eutypella microtheca. Carbendazim, fluazinam, tebuconazole, and prothioconazole + tebuconazole were effective at inhibiting mycelial growth of all Diatrypaceae spp. tested. Pyraclostrobin reduced colony diameter of most of the fungal species by 50% or more. Pyrimethanil was ineffective at reducing mycelial growth of these pathogens. Five of the six fungicides evaluated in this study have shown efficacy in vitro against Diatrypaceae spp. and require further evaluation in the field. This study represents the first approach for fungicide evaluation against mycelial growth of diatrypaceous fungi, other than Ea. lata. It contributes to the development of integrated management strategies for grapevine trunk diseases.