Search

Grapevine Trunk Diseases (GTDs) are major threats in Mediterranean countries, causing economic losses due to reduced grape yields and long-term vine productivity, as well as death of grapevines. A survey was conducted in Piedmont (Northern Italy) during 2021-2022 to investigate the species diversity and distribution of GTD pathogens in this important Italian wine region. Morphological and multilocus phylogenetic analyses (based on ITS, tef1, tub2, act and rpb2) identified species of Botryosphaeriaceae at high frequency, including Botryosphaeria dothidea, Diplodia mutila, Diplodia seriata and Neofusicoccum parvum. Other pathogens commonly associated with GTDs, including Eutypa lata, Fomitiporia mediterranea and Phaeomoniella chlamydospora, were also isolated. Less commonly isolated species included Neocucurbitaria juglandicola, Paraconiothyrium brasiliense, Seimatosporium vitis-viniferae and Truncatella angustata. Pathogenicity tests with two representative isolates of each species were carried out using one-year-old potted grapevine cuttings (‘Barbera’). All isolates (except N. juglandicola) caused brown wood necrotic vascular discolourations on inoculated plants and were successfully re-isolated. Effects of temperature on colony growth were also assessed. For all tested isolates there was no growth at 5°C, only four isolates (Botryosphaeriaceae) grew at 35°C, and optimum growth temperatures were between 20 and 25°C. This is the first record of Paraconiothyrium brasiliense and Neocucurbitaria juglandicola associated with symptomatic grapevines in Italy. [ABSTRACT FROM AUTHOR]

Despite studies associating Fusarium spp. with grapevine decline since late 1970s, no consensus has been reached regarding the roles these fungi play in grapevine health. Recent studies in British Columbia, Canada, assessed prevalence of grapevine trunk diseases (GTDs) in young and mature vineyards, and the presence of GTD fungi in ready-to-plant nursery material sold in Canada. This study characterized the Fusarium spp. isolated from grapevines in BC by sequencing part of the translation elongation factor 1-alpha (TEF1) gene, and carried out pathogenicity studies to determine whether Fusarium plays a role in grapevine decline. Fusarium spp. were isolated from 9.8% of samples collected from young vines (≤ 8-year-old), and 7.3% from mature vines (> 8-year-old), showing decline symptoms in commercial vineyards. Fusarium was also isolated from 43.9% of ready-to-plant dormant grapevines analyzed from four nurseries. Fusarium incidence varied between plants within the same nursery and between plants from the different nurseries. DNA sequences of TEF1 allowed identification of Fusarium oxysporum, F. proliferatum, F. ramigenum, and a Fusarium sp. Pathogenicity studies were conducted in 1-year-old dormant rooted ‘Chardonnay’ plants grafted onto ‘3309C’ rootstock, and treatments included: i) whole plant, ii) trimming of roots, iii) cut at rootstock basal ends, and iv) trimming of roots plus cut at rootstock basal ends. Plants were inoculated using standardized methods, and were then planted in a greenhouse. Fusarium was compared with Dactylonectria macrodidyma, D. pauciseptata and Ilyonectria liriodendri used as positive controls. The Fusarium spp. caused necroses in rootstock roots and basal ends that were similar to those caused by blackfoot fungi. Fusarium spp. and black-foot fungi reduced root and shoot dry weights when compared with non-inoculated controls, but no statistically significant differences were recorded for most treatments. This study is the first in Canada to identify Fusarium spp. from grapevines. Though Fusarium was common in these grapevines, pathogenicity tests suggest that the identified Fusarium spp. were weakly pathogenic to ‘3309C’ rootstock grapevines. [ABSTRACT FROM AUTHOR]

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 woodystem 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. [ABSTRACT FROM AUTHOR]

Black foot is a serious soilborne fungal disease causing decline of young grapevines. Affected plants show brown to dark streaks developing from the rootstock bases, wood necroses at trunk bases, sunken necrotic lesions on roots, and reduced root biomass. Several fungi, commonly known as Cylindrocarpon-like asexual morphs, have been associated with black foot. Nursery vines are infected during rooting in propagation processes, which is important for dissemination of the pathogens. Species associated with black foot in nursery vines produced in Uruguay were characterized by molecular, phenotypical and pathogenicity studies. From 2017 to 2019, 181 rooted vines grafted onto ‘1103P’, ‘SO4’, ‘101-14’, ‘3309C’ or ‘Gravesac’ rootstocks were sampled, and 71 Cylindrocarpon-like fungal isolates were recovered from rootstock tissues (basal ends and roots). Based on multi-gene phylogenetic analyses of HIS3, TEF and TUB2, and supported by phenotypical characterization, five species of Dactylonectria and Ilyonoectria were identified, with D. macrodidyma being the most prevalent followed by D. novozelandica, D. torresensis, D. palmicola and I. liriodendri. Four Ilyonectria isolates could not be identified to species level. Isolate pathogenicity was assessed using healthy rooted ‘Gravesac’ plants. After three months, isolates of all species infected the plants, causing necrotic lesions on roots and reducing root biomass. On average, 39% of ready-to-plant nursery vines were affected by black foot, emphasizing the need to develop integrated management to reduce black foot incidence in Uruguayan grapevine nurseries, based on studies under local conditions. [ABSTRACT FROM AUTHOR]

Good health of grapevine plants is important for productivity and sustainability of newly established vineyards, and accurate detection of bacterial and fungal pathogens is a prerequisite for managing the diseases they cause in nurseries. This study screened marketable, bare-rooted grapevine plants, obtained from different geographical regions of Türkiye, for fungal pathogens associated with grapevine trunk diseases (GTDs). In 2021, 43 grapevine nurseries located in eight provinces were surveyed to reveal the status of GTD pathogens on asymptomatic marketable plants. Fungal pathogens isolated from the roots and basal parts of asymptomatic dormant grapevines were identified using with morphological characteristics and molecular markers, and were subjected to pathogenicity tests. Six species; Cytospora viticola, Diaporthe ampelina, Diplodia seriata, Lasiodiplodia brasiliensis, Neofusicoccum parvum, and Truncatella angustata (associated with dieback), and six species; Cadophora ferruginea, Cadophora luteo-olivacea, Cadophora malorum, Phaeoacremonium minimum, Phaeoacremonium tuscanicum and Phaeomoniella chlamydospora (associated with Petri disease) were identified based on DNA sequencing of ITS and TEF1-α genes. GTD pathogens were detected in 12 and 14 of the 43 nurseries, respectively. Pathogenicity tests on 1103P vines revealed that all species were pathogenic (N. parvum and C. luteo-olivacea being the most virulent), and caused significant wood necroses when compared to non-inoculated experimental controls. This is the first report of C. ferruginea, C. malorum, L. brasiliensis, and P. tuscanicum associated with GTDs in Türkiye. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases cause severe damage in grapevines. Management strategies focus on protection of grapevine pruning wounds using chemical fungicides or biological control agents. Botryosphaeria dieback, caused mainly by Lasiodiplodia spp., is one of the main trunk diseases in northwest Mexico. This study obtained endophytic bacteria and fungi from the heritage grapevine Vitis vinifera cv. ‘Mission’ for potential biological control of Botryosphaeria dieback. A collection of 135 bacterial and 37 fungal isolates were obtained and initially tested for antagonistic activity against Lasiodiplodia brasiliensis. The most promising isolates belonging to Trichoderma and Bacillus spp. were selected and characterized to determine their modes of action. Bacillus isolates produced volatile organic compounds that inhibited growth of Neofusicoccum parvum, and diffusible organic compounds with antifungal effects against L. brasiliensis and N. parvum. Trichoderma isolates produced diffusible organic compounds and were mycoparasites. In greenhouse assays, plants inoculated with three Trichoderma asperellum isolates (T20BCMX, EF09BCMX, and EF11BCMX), B. amyloliquefaciens (BEVP26BCMX) or Bacillus sp. (rbES015), applied preventively in soil, gave up to 50% smaller necrotic lesions when compared with the plants inoculated only with L. brasiliensis. In the field, plants inoculated with three Bacillus isolates (BEVP02BCMX, BEVP26BCMX, BEVP31BCMX) or five Trichoderma (T11BCMX, T15BCMX, T17BCMX, T20BCMX, and EF11BCMX) had lesions up to four times smaller than control plants inoculated only with L. brasiliensis. This study has demonstrated the potential of heritage grapevines to provide biological control agents for Botryosphaeria dieback. [ABSTRACT FROM AUTHOR]

Production from crops of pome, stone fruit, nut, berry fruit, citrus, grapevine, and olive is increasingly threatened by fungal trunk diseases (FTD). These diseases and the consequent production losses are major problems. Many fungi (including Botryosphaeriaceae, Calosphaeriaceae, Diaporthaceae, Diatrypaceae, Nectriaceae, Phaeomoniellaceae, Pleosporaceae, Togniniaceae, Valsaceae) infect host wood, mainly through wounds and subsequent colonization of woody tissues, causing symptoms such as cankers, gummosis, wood rotting, blight and dieback. Propagative plant material, seedlings and fruit play a significant role in pathogen spread. Several abiotic factors (e.g. shifts in cultural practices and climate change) are involved in the disease development. This paper reviews recent literature on FTD of fruit crops, particularly focusing on the European status of pathogen occurrence. Case studies are described related to diseases of apple, citrus, grapevine, berry, nut and stone fruit, and olive trees. Aspects related to epidemiology and the increase in disease incidence along with the future perspectives on the FTD research are also discussed. [ABSTRACT FROM AUTHOR]

In 2017-2018, grapevines of cultivar 'Vermentino' infected with grapevine Pinot gris virus (GPGV) in Sardinia, Italy, exhibited leaf symptoms of mosaic, chlorotic mottling, and curling, and stunted shoots. Disease incidence assessed in 2018 was greater (67%, 103 symptomatic plants out of 153 monitored) than in 2017 (26%, 40 of 153 plants). All symptomatic samples tested by RT-PCR were positive for GPGV in both years, while 70% (53 of 76) of the asymptomatic samples in 2017, and 42% (19 of 45) in 2018, were also positive for GPGV. Characterizing six GPGV isolates from 'Vermentino' by RT-PCR and sequencing of a genomic fragment covering the movement and coat protein genes showed high conservation at the nucleotide level (98.7% to 100.0%) among Sardinian isolates and isolates for which sequence information is available in GenBank. Phylogenetic analysis indicated that most Sardinian GPGV isolates grouped with other European isolates. This is the first characterization of GPGV in a Sardinian vineyard. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases (GTDs) are the most destructive diseases in grape-growing regions worldwide. Black foot is one of the important GTDs affecting young vineyards and nurseries. This disease has not been reported in China. During 2017 and 2019, field surveys were carried out in the Guangxi, Hebei, Ningxia, Shanxi, and Xinjiang provinces of China. Incidence of plants with black foot symptoms was 0.1% to 1% in the surveyed vineyards. Plant samples with poorly developed shoots and canes, chlorotic leaves, and necrotic trunks or roots were collected from the five provinces. In total, 50 fungal isolates were obtained from symptomatic tissues. Based on morphological and multi-gene phylogenetic analyses, five species were identified as Cylindrocladiella lageniformis, Dactylonectria torresensis, D. macrodidyma, D. alcacerensis and Neonectria sp.1. Pathogenicity was assessed using young, healthy detached green shoots of grapevine 'Summer Black' and potted 3-month-old 'Summer Black' cuttings. Inoculated detached shoots developed necroses after 7 d, and inoculated cuttings after 80 d. Fungi were re-isolated from necrotic lesions. Among the five species, D. macrodidyma was the most aggressive. This is the first report of C. lageniformis, D. torresensis, D. macrodidyma, D. alcacerensis, and Neonectria sp. 1 associated with black foot in China. This study has enhanced knowledge of the fungi associated with black foot in China, and will assist development of control measures for this disease. [ABSTRACT FROM AUTHOR]

Botryosphaeria dieback is one of the most prevalent grapevine trunk diseases (GTDs), and is caused by fungi in the Botryosphaeriaceae. Fungi invade grapevine vascular systems mainly through pruning wounds, and cause cankers and necrotic lesions, which lead to grapevine decline and death. Lasiodiplodia theobromae has been reported as a highly virulent pathogen of grapevine, and was previously reported in Mexican vineyards. The taxonomy of Lasiodiplodia was recently revised, adding new species, and some were reduced to synonymy. This study aimed to characterize Lasiodiplodia producing grapevine dieback symptoms in Sonora and Baja California, Mexico. Using the phylogenetic markers tef1-a and ITS regions, Lasiodiplodia brasiliensis, L. crassispora, L. exigua, and L. gilanensis were identified. Lasidiplodia exigua was the most prevalent species. Lasiodiplodia brasiliensis and L. gilanensis were very virulent to 'Cabernet Sauvignon' plants, while L. exigua and L. gilanensis were less virulent, and L. crassispora did not produce lesions at 2 months post-inoculation. The optimum temperature of the Lasiodiplodia spp. was 28°C, but all four species grew up to 37°C, and the isolates of L. exigua grew slowly at 40°C. This is the first report of the four of Lasiodiplodia species in vineyards of Mexico. [ABSTRACT FROM AUTHOR]

The state of Sonora is the main grape production area in Mexico. Grapevine trunk diseases (GTD) are serious disease in this region. During the springs of 2017 and 2018, symptoms of yellow and wilted leaves, and necrotic buds, were observed in several vineyards in Sonora. Affected plants had numerous small, black and bright acervuli. This study aimed to identify the causative agent of this disease. Isolates were obtained from small pieces of damaged plant parts, and were cultured on potato dextrose agar. The developing mycelium was white but turned greyish white after 3 d. Multi-shaped black mucilaginous droplets appeared in the cultures after 2 d, and the agar in Petri dishes was completely covered with mycelium after 7 d, and the colonies had five or six rings with large numbers of conidiomata. Conidia were hyaline or light cream, fusiform, oval or ellipsoid, with truncated bases and narrow almost pointed apices, and were 6--10 mm long and 2--3 mm wide. Phylogenetically analysed concatenated sequences of the DNA from two representative isolates, from the internal transcribed spacer region, and large ribosomal subunit, showed they were in a separate clade which aligned with several strains of Greeneria uvicola, confirming the presumptive morphological identity of the isolates. This cosmopolitan ascomycete is responsible for bitter rot of grapes, but the role of this fungus as a cause of grapevine trunk diseases is little known. Pathogenicity tests of the isolates were performed on 1-year-old 'Passion Fire' grapevines plants, one of the new cultivars planted in Sonora. All of strains G. uvicola were pathogenic, and the fungus was recovered from the lesions, fulfilling Koch's postulates. This is the first report on the pathogenicity of G. uvicola in wood tissues of Vitis vinifera in Mexico. [ABSTRACT FROM AUTHOR]

Esca is one of the most widespread grapevine trunk diseases affecting vineyards. This complex disease leads to leaf alterations, wood necrosis and eventually to plant death. Esca symptoms are caused by several fungi inhabiting the xylem of host plants and degrading the wood structure. The main pathogens causing the disease are Phaeomoniella chlamydospora, Phaeoacremonium minimum, Fomitiporia mediterranea and other wood-rotting basidiomycetes. Grapevine susceptibility to esca can be predisposed by several factors, especially climate, vine age, and cultivar. An experiment was carried out (in 2015) to assess if esca expression on leaves could also be clone-dependent. Chardonnay clones 76 and 95 grown in the same plot were compared according to their developmental and physiological traits, metabolome, and foliar symptom expression. Leaves were sampled during summer on visually healthy vines as controls (C), and from asymptomatic (D-) and symptomatic (D+) shoots of esca-affected vines. Analysis of their metabolomes highlighted a clone-dependent metabolite fingerprint associated to esca expression. Opposite variations of specific metabolites were found between C and D+ leaves of both clones. The experiment was repeated (in 2018). Leaf samples could be discriminated, especially the C and D+ samples for each clone, but the differences were less marked than in the first experiment. Discriminant compounds were all different between the two experiments, and showed no opposite variations between C and D+ samples of both clones, which indicated variable metabolite responses from year to year for both clones. These results confirm that the leaf metabolite fingerprint associated to esca expression is clone-dependent, and is year-dependent in intensity and nature. [ABSTRACT FROM AUTHOR]

Neofusicoccum australe is one of the most important Botryosphaeriaceae pathogens occurring on fruit and vine crops. This fungus was recently taxonomically reassessed, identifying N. stellenboschiana as a separate species. Previous pathogenicity studies used N. stellenboschiana and N. australe isolates as N. australe, so assessment of the pathogenicity of these two species on grapevine and other hosts was required. A pathogenicity trial was conducted on detached shoots of grapevine, plum, apple, olive and Peruvian pepper tree. Shoots were individually inoculated with 11 N. australe and eight N. stellenboschiana isolates originally isolated from grapevine, plum, apple, olive, Peruvian pepper and fig. Both species formed lesions on all five hosts and were reisolated 5 weeks post-inoculation. In general, the largest lesions were formed on plum and smallest on Peruvian pepper. Isolate host origin did not influence ability to cause lesions on other hosts. Isolates of N. australe and N. stellenboschiana differed in virulence on the various hosts, ranging from those that caused the largest lesions, a group causing intermediate lesions, and another causing lesions similar to uninoculated controls. The study demonstrates that N. australe and N. stellenboschiana isolates originating from various fruit hosts can infect alternative hosts including grapevine and other major fruit crops. [ABSTRACT FROM AUTHOR]

Lasiodiplodia (Botryosphaeriaceae) includes fungi that are considered among the most aggressive to grapevine, capable of causing cankers and necrotic lesions which eventually lead to death of host plants. A common characteristic of this genus is the presence of melanin in conidia and mycelium. Melanin is produced by the oxidation of phenolic and/or indolic compounds. For some fungi, this pigment is an essential factor for pathogenicity. This study characterized the types and the roles of melanin produced by Lasiodiplodia gilanensis. Using specific melanin inhibitors, L. gilanensis was shown to synthesize DOPA-melanin, DHN-melanin, and pyomelanin. DOPA-melanin was shown to be involved in production of aerial mycelium and protection against enzymatic lysis and oxidative stress; DHN-melanin to be involved in ramification of mycelium when exposed to nutrient deficiency; and pyomelanin to be related with hyphae development. The fungus used tyrosine as a precursor of DOPA-melanin and as carbon and nitrogen sources, and produced melanin inside the piths of infected plants. Genes involved in melanin synthesis were conserved among the Botryosphaeriaceae, highlighting the importance of melanin in this family. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases (GTDs) are increasing in vineyards in many grape production regions. Among the pathogens causing these diseases, Neofusicoccum parvum, is one of the most frequent and virulent. To control GTDs, biocontrol is being developed using plant beneficial microorganisms. Strains of the oomycete Pythium oligandrum have been shown to naturally colonize grapevine roots in vineyards in several countries in Europe. This study examined the ability of the root-coloniser P. oligandrum to induce grapevine resistance against N. parvum, by deciphering the gene expression changes in a set of 62 genes involved in different grapevine defence pathways. Two greenhouse assays showed that the wood necrosis of vine cuttings caused by N. parvum was reduced by 65% when P. oligandrum colonized root systems of the plants. The relative expression levels of selected genes in the host trunks were studied by real-time PCR. Plant responses were assessed after inoculation by P. oligandrum and/or N. parvum, at three different sampling time points (0, 14 and 150 d after N. parvum inoculation). Sampling time influenced gene expressions for the different inoculation treatments. At each sampling time, specific host responses to the different treatments were also detected, for controls, and for inoculations with P. oligandrum, N. parvum or P. oligandrum + N. parvum. When P. oligandrum colonized grapevine root systems, inoculation with the pathogen was associated with increased up-regulation and over-expression of particular genes, including those regulating Pathogen-Related proteins, cell wall reinforcement proteins and hormone signalling pathways. A priming effect of the grapevine defence system was induced in roots colonized by P. oligandrum. [ABSTRACT FROM AUTHOR]

Grapevine Trunk Diseases (GTDs) cause important economic losses in vineyards. Diagnosis of pathogens causing GTDs is usually achieved using culture methods from symptomatic plants, but these methods may not be definitive. This study aimed to detect three fungi associated with GTDs in Chile (Diplodia seriata, Phaeomoniella chlamydospora and Eutypa lata) using qPCR methods, after extracting DNA from asymptomatic woody pruning material taken from 912 grapevine plants and 346 rootstocks. Pathogen incidence and distribution across different regions, vineyards, grape and wine cultivars, plant ages and rootstocks were determined. Forty percent of assessed grapevine plants and 42% of rootstocks were positive for the assayed GTD pathogens. The fungus with the greatest incidence was D. seriata (36% of plants and 30% of rootstocks), followed by E. lata (6% of plants and 20% of rootstocks) and P. chlamydospora (4% of plants and 5% of rootstocks). Positive relationships were detected between the presence of D. seriata and P. chlamydospora and grapevine age. However, the three fungi were randomly distributed across graprevine plants and rootstocks since none of the assessed factors had statistically significant influence in their distribution. This study is the first to assess incidence and distribution of E. lata in Chile. The qPCR-based method described could be used for detecting fungi in asymptomatic nursery plants, and be used to avoid distribution of infected plants into new vineyard plantings. [ABSTRACT FROM AUTHOR]

The seasonal abundance of Diatrypaceae spores was studied in southern California's desert table grape-growing region of Coachella Valley. Glass microscope slides covered with petroleum jelly were placed in a mature cv. Mid-Night Beauty® vineyard, and collected weekly from September 2006 to May 2009 (1400 samples for 140 consecutive weeks). Overall, Diatrypaceae-like colonies were recorded from Petri plates after processing spore traps in 93 (66%) of 140 weeks. Phylogenetic analyses showed Eutypella citricola and Eutypella microtheca to be the Diatrypaceae spp. captured from the spore traps. Though spores were captured throughout each year, their incidence varied among the different seasons. The greatest number of Eutypella spores were captured in autumn (38.7% of the total) followed by winter (30.6%), summer (19.7%), and spring (11%). The greatest numbers of spores were captured in October each year (15.7%) and least in June (1%). Eutypella spore release was correlated with rainfall only in 26 (28%) of the 93 weeks that spores were captured during the study. Analysis of diseased samples collected from the cv. Mid-Night Beauty® vineyard showed that E. citricola, E. microtheca and E. scoparia were the most prevalent fungi isolated from cankers. A pathogenicity study showed that E. citricola and E. microtheca isolates collected from spore traps caused larger vascular necrosis than the non-inoculated controls, indicating their role as pathogens on grapevines. This study has demonstrated Eutypella spp. to play an important role in grapevine health under desert growing conditions of southern California. In addition, and contrary to what it is largely accepted, results from this research suggest that Diatrypaceae spore release can occur in the absence of precipitation. This study expands current knowledge on epidemiology of Diatrypaceae spp. other than Eutypa lata, and provides important information for enhancing control strategies against grapevine trunk diseases under desert growing conditions. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases (GTDs) are one of the most economically important diseases of grapevines, causing yield reductions and limiting vineyard lifespans. Fungal pathogens responsible for GTDs primarily infect grapevines through pruning wounds. The lack of systemic fungicides to stop the advance of fungi in vine vascular systems makes the use of pruning wound protection with either synthetic chemicals or biological control agents (BCAs) the main available GTD control strategy. Demands for sustainable grape production and increasing limitations on pesticide usage have raised interest in potential use of BCAs as pruning wound protectants against GTDs. The objectives of this study were to characterize 16 Trichoderma isolates from southern Italy using molecular methods, and to evaluate their potential activity as BCAs in vitro against the GTD canker-causing fungi Diplodia seriata, Eutypa lata and Neofusicoccum parvum. Molecular studies along with phylogenetic analyses identified eight species, including Trichoderma atroviride, T. guizhouense, T. harzianum, T. koningiopsis, T. longibrachiatum, T. paratroviride, T. paraviridescens, T. spirale, and one unidentified Trichoderma sp. All these species had optimum mycelium growth between 25 and 35°C. In vitro dual culture experiments assessed antagonistic capabilities of all the Trichoderma isolates against D. seriata, E. lata and N. parvum, and showed that the isolates inhibited mycelial growth of the pathogens by up to 70%. The most inhibitory isolates were tested in planta for capability to protect pruning wounds against D. seriata and N. parvum in a detached cane assay. All the selected Trichoderma isolates gave >80% control of D. seriata and 60% control of N. parvum, and protected pruning wounds for up to 21 d after treatment. [ABSTRACT FROM AUTHOR]

After the first report of grapevine decline caused by Botryosphaeriaceae in Sicily in 2007, epidemiological studies carried out in mature vineyards until 2011 confirmed the widespread occurrence of "Botryosphaeria dieback" and the "Esca complex" disease. Dieback symptoms were also recently observed in two young vineyards in Partanna and Castellammare del Golfo in western Sicily (Trapani province). Declining vines were inspected for grapevine trunk disease (GTD) symptoms, and were uprooted and submitted for analyses. Fungal isolates were collected and identified using culturing and molecular analyses. One isolate per identified species was inoculated to three grapevine shoots to evaluate pathogenicity and fulfil Koch's postulates. Several GTD Botryosphaeriaceae pathogens in the genera Cadophora, Ilyonectria, Neonectria, Phaeoacremonium and Phaeomoniella were isolated from the symptomatic young vines. Artificial inoculation confirmed the pathogenicity of these fungi. In addition, virulence variability was observed among the isolates, with P. chlamydospora causing the largest lesions. The different species were associated with specific symptoms and/or host vine parts, especially in the roots and around the grafting areas. Several fungi associated with Petri disease and black foot were shown to be responsible of young vine decline. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases (GTDs) are major biotic factors reducing yields and limiting vineyard economic life spans. Fungi in the GTD complex cause a range of symptoms in host plants, although these pathogens are slow wood colonizers and potentially latent pathogens. Understanding has recently increased on the possible roles that GTD fungi may play as latent pathogens, and how this can be translated into disease management. This paper summarizes evidence for the latent nature of infections by these fungi in grapevines and other hosts. Abiotic and biotic stressors have been associated with symptom expression in many hosts, but limited information is available regarding their roles in symptom development in grapevines. Based on research conducted in other pathosystems, this review discusses how abiotic and/or biotic stress factors may influence the transition from the endophytic to the pathogenic phases for GTD fungi. Potential methods for stress mitigation are also outlined as alternative GTD control strategies to minimize the economic impacts that that these diseases have on grape production. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases are major threats to viticulture. A diverse array of Ascomycetes and Basidiomycetes can affect perennial and, indirectly, annual organs of grapevines. Early infections produce wood discolouration, brown wood streaking, black spots and wood necroses. However, all wood symptoms are internal, making nondestructive identification of infected plant material very difficult. To date, there are no nondestructive methods for detecting the presence of developing wood infections, neither in nursery nor field conditions. This means that infected propagation material is planted into new vineyards. Three technologies, magnetic resonance imaging (MRI), computed tomography scan (CT scan) and X-Ray microtomography (Micro-CT), were assessed for determining presence, location and extent of grapevine wood defects caused by fungal infections. Results indicated that MRI lacked resolution to differentiate between asymptomatic and defective wood. CT scan analyses revealed substantial differences in radiodensity when comparing asymptomatic wood to wood with black spots, necroses, and decay. Greatest resolution was achieved with micro-CT (6 μm). This technology precisely distinguished asymptomatic from defective wood, for wood symptoms including necrosis, decay, black spots and brown wood streaking affecting individual xylem vessels, in perennial wood and canes. Micro-CT was thus the best method for nondestructive identification of wood defects resulting from infections. Further work is required to make this technology feasible for the rapid screening of grapevine nursery stock, both in nurseries and at planting. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases (GTD) are important threats to long-term longevity, productivity, and profitability in all grape production systems. Botryosphaeria dieback is caused by at least 32 Botryosphaeriaceae fungi. The main symptoms of this disease on grapevines are wedge-shaped cankers in the trunks, general decline and eventually death of affected plants. Pathogens from this family have broad host ranges and varying virulence. This study aimed to compare, and gain some insight into how, Lasiodiplodia gilanensis, Diplodia seriata, and D. corticola colonize grapevine tissues. In vitro studies using pycnidiospores as inoculum, showed that the presence of grapevine wood affected spore germination, hyphal growth and branching, and biomass production, especially in L. gilanensis. In planta, microscopy revealed the use of xylem vessels as the preferred sites of pathogen entry, and differences in growth and hyphal branching among species. Lasiodiplodia gilanensis produced cellulases at the beginning of the pathogen/host interaction to degrade plant tissues and invade parenchymal tissue, while D. seriata and D. corticola grew endophytically in the first stages of grapevine colonization. [ABSTRACT FROM AUTHOR]

Among all causes of grapevine decline, Grapevine Trunk Diseases (GTDs) are major concerns for grape growers. This paper reviews knowledge and proposes hypotheses on two major GTDs, esca and Botryosphaeria dieback, and assembles a conceptual model. The objective was to collect information into a sequence, from grapevine nursery propagation processes, through foliar symptom expression, to plant death in mature vineyards. Pathogen infection and colonization steps in woody vine tissues, and the hypotheses that have been formulated to explain the outburst of foliar symptoms, are reported and discussed. Factors that could aggravate or repress GTD symptoms and incidence expansion are also addressed. Vine physiology and pathology together could expand understanding of these diseases. Knowledge and hypotheses that need validation are summarized, and a conceptual model is proposed to explain the occurrence of symptoms and the influencing factors. The model could be useful to cope with the complexity of GTDs, and as a starting point for research to unravel knowledge gaps and suggest new disease management strategies. [ABSTRACT FROM AUTHOR]

Botryosphaeria dieback (BD) is an important trunk disease affecting grapevines. Several Lasiodiplodia species have been shown to be involved in BD affecting the perennial organs of grapevine, mainly causing cankers. (R)-(-)-mellein and tyrosol, two well-known fungal phytotoxins, were isolated from the organic extract of culture filtrate of Lasiodiplodia laeliocattleyae (syn. egyptiacae), which had been isolated from grapevines affected by BD in Brazil. This increases knowledge of the secondary metabolites produced by Lasiodiplodia species, confirming that (R)-(-)-mellein is a toxin typically produced by Botryosphaericeae species. [ABSTRACT FROM AUTHOR]

A survey was carried out in 22 European and some non-European Mediterranean countries in 2015 and 2016, to gain insights into the main fungal grapevine trunk diseases (GTDs) in Europe. Information was obtained from 105 viticulture regions, representing approx. four million ha of vineyards. Vintage and table wines are the main industry products, followed by nursery plants and table grapes. Diverse scion cultivars are grown, with 13 cultivars providing 50% of survey respondent production, and Riesling Italico, Chardonnay, Cabernet Sauvignon and Merlot predominating. The five most used rootstocks are SO4, 110R, K5BB, 41B and 1103P, together representing about 50% of survey respondent production. Despite the diversity of grapevine training, Guyot and cordon remain the most widespread methods, and grapevines are mainly handpruned. The use of pneumatic shears and mechanical pruning is becoming more common in some countries. The survey questionnaire proposed a simplified set of symptoms or diseases occurring in mature vineyards [apoplexy, esca complex leaf symptoms (including Grapevine Leaf Stripe Disease, GLSD), dead cordon, Eutypa related dieback, Botryosphaeria or unidentified agent dieback, Phomopsis cane and leaf spot]. Apoplexy and esca/GLSD, defining the esca complex, were the most frequent and increasing syndromes in almost all countries, except Israel and the United Kingdom, where these diseases are not present or not recorded in the survey. Dead cordon and Phomopsis cane and leaf spot were mentioned as occurring in a large number of regions but not frequently. Within individual countries, the profile of GTDs varied according to the region, and to pedo-climatic and production conditions. GTDs on young vines were uncommon, but remain a subject of concern in some of European countries with large nursery production. This overview on spread and relevance of GTDs in Europe and related aspects will be a useful starting point for policy makers and for collaborative research on factors contributing to the increasing disease incidence of GTDs. [ABSTRACT FROM AUTHOR]

This review compiles the available knowledge on the triple impact of hostpathogens- environment in the progress of the esca disease complex of grapevine. The perennial crop grapevine encounters different biotic and abiotic factors responsible for numerous changes at the various growth stages. This review provides increased understanding of the esca disease complex, with emphasis on (1) the nature of esca-associated fungi as endophytes or pathogens in grapevine, (2) the importance of grapevine genotype and age in relation to resistance or susceptibility to the pathogens, (3) the significant effects of climatic changes, especially drought, on pathogen development and symptomatology, and (4) the physio-biochemical changes in the grapevines arising from the biotic and abiotic interactions. Drought often provides conditions favouring disease development in plants. Physiological and biochemical changes in plants play critical roles in this topic. The constantly increasing economic impacts of esca disease in many grape-producing countries, and the broad lack of knowledge so far, require precise studies on the transcriptional responses to biotic and abiotic factors in grapevines, as effects of "climate change" develop. On the viticultural side, improved management of water and adjusted nutrition balance in vineyards may become useful strategies to mitigate the widespread damage caused by grapevine wood pathogens. [ABSTRACT FROM AUTHOR]

Grapevine leaf stripe disease (GLSD) symptom expression was analysed in four vineyards and four cultivars, in Sardinia (Italy), taking into account ten-year annual and five-year monthly surveys. The cumulative incidence of symptomatic plants reached high values on Sauvignon blanc, Cabernet sauvignon and Cannonau (81.9, 79.4 and 66.5% respectively), but low on Merlot (25.1%). Symptoms appeared during or before the 50% flowering stage and maximum increments were assessed in June and partially in July. Annual incidence of foliar symptoms fluctuated in the ten years of the survey. Positive regressions were found between incidence of vines that exhibited foliar symptoms in year n but were symptomless in year n-1 and rain parameters in the 30 days after stabilization of mean temperature around 10°C, when colonization of pruning wounds begins. This relationship could suggest the involvement of new infections or re-infections on symptom expression in the following growth season. Significant regressions between incidence of vines that exhibited foliar symptoms in year n but were symptomless in the year n+1 and climatic parameters were also recorded. High temperatures and low rainfall in the period from pre-flowering to veraìson were conducive to a higher number of asymptomatic plants. Regarding monthly foliar symptoms evolution, an increase in temperature from 50% sprouting until June led to a greater number of new symptomatic plants. On the other hand, a smaller percentage of new symptomatic plants was associated with an increase in temperature from June to July, which may have influenced vine water balance and transport of toxins by the sap flow. [ABSTRACT FROM AUTHOR]

A field experiment was conducted between mid-August 2016 and mid-October 2017 in four table-grape vineyards in the Siriji Valley, Pernambuco State (Northeastern Brazil), to study the conidial dispersal dynamics of Botryosphaeriaceae fungi, causing grapevine trunk diseases (GTDs). Conidial dispersal was assessed by exposing microscope slides coated with Vaseline close to symptomatic plants and pruning debris. The slides were replaced every 2 weeks for a total of 30 sampling periods. Conidia of the genera Diplodia, Lasiodiplodia and Neofusicoccum were enumerated based on morphological characters. Conidia were collected from all four table-grape vineyards, confirming that these fungi are present as aerial inoculum and could be associated with GTDs in the region. Conidia of Diplodia and Lasiodiplodia were present in all the sampling periods, and those of Lasiodiplodia were the most abundant. Conidia of Neofusicoccum were found less frequently, and in less numbers than the other genera. Significant correlation between the number of conidia sampled and the amount of rain was observed for Diplodia only. Greater numbers of conidia were collected from pruning debris than from symptomatic plants. For Diplodia and Lasiodiplodia, the numbers of conidia gradually increased in September, increased sharply between March and June, and then decreased. These dynamics were described by a logistic equation, with hydro-thermal time (i.e., a combination of degree-days and relative humidity) as the independent variable (R2 > 0.998). [ABSTRACT FROM AUTHOR]

Black foot disease (BFD) and crown and root rot (CRR) are important soilborne diseases that affect young grapevines in nurseries and vineyards. A 3-year survey (2013-2015) of five open-field grapevine nurseries was conducted in the Western Cape Province of South Africa. The survey involved the isolation of BFD and CRR pathogens from grafted rootstocks (ten plants per nursery, per year) that were rooted in soil for 1 year. In 2013 and 2015, grapevines were sampled, while in 2014, sampling was focused on rotation crops and weeds (ten plants each). The rotation crops included white mustard, lupins, canola, triticale and forage radish. The weed species sampled included Johnson grass, ryegrass, winter grass, Cape marigold and corn spurry. Soil samples from ten sites per nursery were also collected in close proximity to the sampled plants, at depths of 0-30 cm and 30-60 cm (ten samples per depth). Isolations were made from the grapevines, rotation crops and weeds. Pathogen detection and quantification in the soil were determined using quantitative real-time polymerase chain reaction technology. The predominant BFD pathogens isolated from grapevines were Campylocarpon fasciculare, Ca. pseudofasciculare and Dactylonectria macrodidyma. The predominant CRR pathogens were Pythium irregulare and Phytopythium vexans. Dactylonectria macrodidyma, D. novozelandica, D. pauciseptata, Py. irregulare, Py. ultimum var. ultimum and Py. heterothallicum were isolated from triticale roots. Dactylonectria spp. were also isolated from corn spurry, while Py. irregulare and Py. ultimum var. ultimum were isolated from numerous weeds and rotation crops. Mean soil DNA concentrations of Ilyonectria and Dactylonectria were from 0.04 to 37.14 pg μL-1, and for Py. irregulare were between 0.01 and 3.77 pg μL-1. The Phytophthora mean soil DNA concentrations ranged from 0.01 to 33.48 pg μL-1. The qPCR protocols successfully detected and quantified BFD and CRR pathogens in grapevine nursery soil. This is the first report of D. pauciseptata and D. alcacerensis in South African grapevine nurseries. [ABSTRACT FROM AUTHOR]

Nineteen species of Phaeoacremonium have been associated with grapevines in South Africa, of which only six species have been confirmed as pathogens through pathogenicity tests conducted on field-grown grapevines. This study determined the pathogenic status of ten Phaeoacremonium spp. recently found for the first time on South African grapevines. These were: Pm. australiense, Pm. austroafricanum, Pm. fraxinopennsylvanicum, Pm. griseo-olivaceum, Pm. griseorubrum, Pm. iranianum, Pm. italicum, Pm. prunicolum, Pm. scolyti and Pm. sicilianum. In the pathogenicity tests, Ph. parasiticum was used as the positive control, and sterile water as the negative control. Up to three isolates were used per species, depending on isolate availability. Freshly cut pruning wounds in a 9-yearold Cabernet Sauvignon vineyard in Stellenbosch, South Africa, were inoculated with 200 conidia of each fungus per wound. Inoculated pruning wounds were removed after 18 months, cut longitudinally and lesion lengths were measured. Re-isolation proportions were determined by conducting isolations from inoculated spurs. All the inoculated isolates successfully colonized pruning wounds, and caused lesions that were significantly different from the negative control. All isolates were re-isolated at proportions varying from 28.6 to 85.7%. Phaeoacremonium griseo-olivaceum STE-U 7859 produced the longest lesions (mean = 79.5 mm) and Pm. iranianum STE-U 6998 the shortest (62.0 mm). No statistically significant differences in mean lesion lengths were observed between the inoculated species. There were also no significant differences between isolates of the same species, except in Pm. prunicolum where isolate STE-U 5968 produced longer lesions (mean = 77.3 mm) than STE-U 7857 (62.3 mm). This study confirmed the capabilities of all the tested Phaeoacremonium spp. to infect grapevine pruning wounds and cause lesions. The study also confirmed the importance of pruning wounds as ports of entry by these pathogens into host plants. [ABSTRACT FROM AUTHOR]

Two vineyards in the Abruzzo Region, central Italy, affected by grapevine leaf stripe disease (GLSD), were monitored for incidence and severity of foliar symptoms of the disease for 21 consecutive years (1994 to 2014). Each year, rainfall and temperature were recorded. Correlations between symptom incidence or severity and rainfall or temperature of different periods of the year or single months were assessed. July rainfall and temperature were highly correlated with incidence and severity of leaf symptoms. The vineyards were characterized by high longevity, vigour and yields, and a particular dynamic of GLSD. In the period following 2005, the year of peak vine mortality, there was a decrease of the expression of foliar symptoms, which was not correlated with both of the climate parameters. Greater mortality occurred for vines showing severe symptoms at the first appearance of GLSD than for vines with low severity. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases (GTD) are one of the most important constraints for grapevine and wine production worldwide. Most of the published studies on these diseases in Europe relate to the major vine growing regions mainly located in southern Europe. This is the first study of GTD incidence and associated fungal pathogens in Czech vineyards, as an example of the north-eastern European grape-growing region. Annual incidence of GTD symptoms in vineyards of cvs. 'Chardonnay' and 'Cabernet Sauvignon' in three Czech locations was surveyed. On average, 3.7% of the 'Chardonnay' plants showed GTD symptoms and 0.7% suddenly collapsed each year. Within the 'Cabernet Sauvignon' vineyards, 10.1% of the plants showed GTD symptoms and 2.5% suddenly collapsed. Several fungal pathogens were associated with the suddenly collapsed grapevines, and the most frequent was Phaeomoniella chlamydospora (77% of analyzed grapevines), followed by Eutypa lata (62%), Diaporthe ampelina (31%), Botryosphaeria dothidea (15%) and Fomitiporia mediterranea (15%). [ABSTRACT FROM AUTHOR]

Grapevine leaf stripe disease (GLSD) is the most important syndrome of the esca disease complex. GLSD foliar symptoms are associated with grapevine yield losses and decline in vigour of host plants. Relationship between incidence and severity of GLSD symptoms and reductions grape quantity and quality has been demonstrated. In 2010-2012, foliar applications of mixtures of fertilizers based on calcium, magnesium and seaweed reduced symptom expression and increased yield quantity and quality. In the present study, mixture applications were carried out in 2013-2015 in different vineyards located in Abruzzo and Emilia-Romagna Regions (north-central Italy). These treatments reduced GLSD symptom incidence and severity, and applications of seaweed without calcium and magnesium was not effective. This confirmed involvement of the nutrients in the reduction of leaf symptom expression. Mechanical properties and absorbance difference measurements demonstrated increased berry quality from vines treated with the mixture. In trials carried out in 2015, the efficacy of the mixture applied in tank mix with other pest and disease control products was not reduced. We conclude that applications of calcium, magnesium and seaweed mixtures are effective for reducing the impacts of GLSD in vineyards. [ABSTRACT FROM AUTHOR]

The pathogens Phaeomoniella chlamydospora and Phaeoacremonium minimum are associated with different syndromes of the esca disease complex affecting grapevine propagation material, and young and adult plants. Infections by these fungi occur in grapevine nurseries and in vineyards, with disease control strategies providing limited protection in both cases. Several chemicals are effective in vitro against these two pathogens, but treatment of infected plants, especially endotherapy, has not yet proven satisfactory. Five chemicals (elemental silver, fosetyl- Al, glutaraldehyde, hydrogen peroxide and Blad-containing oligomer) were tested in vitro, with the first four also tested in planta, by means of endotherapy, against Pa. chlamydospora and Pm. minimum. All chemicals were effective in vitro for preventing growth of both pathogens, at different concentrations. Endotherapy of rooted grapevine cuttings (cv. Touriga Nacional) was effective against Pa. chlamydospora for all the tested chemicals, with reductions in the frequency of re-isolation of this pathogen of 91-95% (glutaraldehyde), 68-96% (hydrogen peroxide), 68-77% (elemental silver) and 58-59% (fosetyl-Al) when compared with the water-treated experimental controls. The only treatment that was effective against Pm. minimum was glutaraldehyde, providing a 75-83% reduction in re-isolation frequency. These results indicate that endotherapy of young grapevines during early stages of infection may be an effective control strategy, especially against the wood pathogen Pa. chlamydospora. [ABSTRACT FROM AUTHOR]

Grapevine Trunk Diseases (GTDs), particularly esca, are major concerns in Spain. This study characterized the fungal and bacterial communities in a 30-year-old ‘Cabernet Sauvignon' vineyard in Catalonia, Spain. Six symptomatic vines expressing esca-foliar symptoms and six additional asymptomatic plants were surveyed. Non-necrotic and necrotic tissues were sampled from rootstocks, trunks and cordons of the selected vines. Fungal isolations and molecular techniques were used in combination to investigate the endophytic microflora and to characterize the fungal and bacterial diversity of the vines. Pathogenic fungi involved in GTDs were identified, and the associations were assessed between all the isolated fungal taxa and the health status of vines, host parts and tissue types. Phaeomoniella chlamydospora and Diplodia seriata were found in non-necrotic tissues, whereas Fomitiporia mediterranea was mainly found in soft-rot tissues, and Neofusicoccum parvum and Eutypa cf. lata in hard necrotic tissues. Several Alternaria and Trichoderma species were isolated, mainly from non-necrotic tissues. The single strand conformation polymorphism fingerprinting method showed differences in bacterial and fungal communities between the different types of tissue in healthy and diseased vines. However, no differences were detected in these microbial communities between non-necrotic tissues from asymptomatic and symptomatic vines. Two frequently-isolated species of Paraconiothyrium were tested for pathogenicity, but their pathogenic roles on grapevines was unclear. [ABSTRACT FROM AUTHOR]

Grapevine trunk diseases (GTDs) are one of the most important groups of fungal diseases affecting grapevine plants worldwide. One of the main causes of GTDs infection occur during nursery plant production processes. The phytosanitary status was determined for 150 young grapevine plants (two varieties grafted onto different rootstocks) that were produced in three European nurseries. Some plants were analyzed upon submission, while others were assessed after up to 12 months growth in a greenhouse. Fungal species associated with GTDs were identified and characterized from the scions, graft unions, rootstocks, or roots. A total of 449 fungal isolates associated with GTDs were obtained, and 20 species were identified by morphological characteristics and DNA analyses. Five species were involved in Botryosphaeria dieback, six in black foot disease, six in Diaporthe dieback, and three in Petri disease. Incidence of GTDs on grapevine plants was between 81 and 100%, with different diseases varying between rootstocks and grapevine varieties. Isolates of other fungal genera not involved in the GTD complex were also detected, including Colletotrichum, Fusarium, and Rhizoctonia. The high presence of GTDs during nursery production of grapevine plants raises the need to implement effective control methods that could prevent the spread of these diseases to vineyards. [ABSTRACT FROM AUTHOR]

Since the early 1990s, grapevine trunk diseases (GTDs) have posed threats for viticulture. Esca complex, Eutypa- and Botryosphaeria- diebacks, mostly detected in adult vineyards, are currently responsible for considerable economic losses in the main vine-growing areas of the world. Other GTDs, such as Petri- (Esca complex) and Black-foot diseases, are emerging problems in grapevine nurseries (resulting in grafting failures and/or loss of saleable plants) and in young vineyards. The impacts of GTDs in modern viticulture depend on several factors, some related to their complexity, and others linked to host plant characteristics, changes in vineyard management and to the scarcity of simple tools for their control. For these reasons control of GTDs remains difficult, also depending on knowledge transfer from research to field and vice versa. This paper outlines the main preventive and curative techniques currently applied, scientifically tested or not that have resulted from the outcomes of "Winetwork", a European Union funded project with special emphasis on the promising and innovative approaches. [ABSTRACT FROM AUTHOR]

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]

Young grapevine plants with decline and wood necrosis symptoms were collected from vineyards and nurseries in tire Apulia and Molise regions, Italy, from 2013 to 2015. Isolations of fungi were prepared from 45 diseased grapevine plants, and the cultures were identified. Several species commonly associated with Petri disease, Botrvosphaeria dieback, and black foot disease were isolated. A detailed study was carried out, and 182 isolates resembling Cylindrocarpon-like asexual forms were identified through morphological characterisation and DNA analysis of internal transcribed spacer regions 1 and 2 of the rRNA gene and the partial β-tubulin gene. Dactylonec-tria torresensis and Uyonectria liriodendri were identified based on morphological features and the partial histone 3 gene, so these fungi can be defined as the causal agents of black foot on grapevine for the first time in Italy. Thelonectria blackeriella is also described as a new species, through morphological characterisation and multigenic analysis using sequence data for five loci (large subunit RNA, internal transcribed spacers, β-tubulin, actin, RNA polymerase II subunit 1). This new species was associated with black foot symptoms according to preliminary pathogenicity tests, with representative isolates of each of the three species. Pathogenicity tests showed that these species can cause black streaking in the wood of 1-year-old grapevine rootstock shoots. The identification of D. torresensis, 1. liriodendri and T. blackeriella from young grapevine plants and rooted rootstock highlights the importance of black foot disease in Italy, which has previously been overlooked. [ABSTRACT FROM AUTHOR]

Vineyards containing vines affected with grapevine leaf stripe disease (GLSD), one of the diseases of the esca complex, suffer losses in grape yield and quality every growing season. To examine the relation between GLSD foliar symptoms and levels of phytoalexins in grapevine, phytoalexin levels were monitored in the leaves of symptomatic, asymptomatic/diseased, and healthy grapevine leaves, at various growth stages, in two vineyards in Italy, over four growing seasons. At the same time, the leaf symptoms of the vines at some of those growth stages were recorded in each vineyard and in each growing season. The compounds extracted and identified were: trans-resveratrol, trans-pterostilbene, trans-ε-viniferin and trans-δ-viniferin. The most common phytoalexin found was resveratrol. Amounts of all the phytoalexins were generally greater in symptomatic leaves than in asymptomatic/ diseased or healthy leaves. In symptomatic leaves, resveratrol levels were greatest at pre-bunch closure, and peaks in pterostilbene occurred at the same time. Leaves of each category (symptomatic, asymptomatic/ diseased, healthy) had lower amounts of these compounds at veraison and generally higher amounts at the stages of harvesting and/or the softening of berries. It seems therefore that the formation and pattern over time of the phytoalexins was linked to the growth stage of the vines. Leaf symptoms never occurred before pre-bunch closure, but became much more common from veraison to harvest. This study provides evidence of a relationship between the levels of phytoalexins, grapevine growth stage, and the seasonal pattern of development of GLSD symptoms. [ABSTRACT FROM AUTHOR]

Pestalotioid fungi associated with grapevine wood diseases in France are regularly found in vine growing regions, and research was conducted to identify these fungi. Many of these taxa are morphologically indistinguishable, but sequence data can resolve the cryptic species in the group. Thirty pestalotioid fungi were isolated from infected grapevines from seven field sites and seven diseased grapevine varieties in France. Analysis of internal transcribed spacer (ITS), partial β-tubulin (TUB) and partial translation elongation factor 1-alpha (TEF) sequence data revealed several species of Neopestalotiopsis, Pestalotiopsis and Truncatella associated with the symptoms. Three Neopestalotiopsis spp. and one Pestalotiopsis sp. are reported for the first time associated with wood diseases in grapevine in France and worldwide, and include Neopestalotiopsis asiatica, N. javaensis, Neopestalotiopsis sp. and Pestalotiopsis biciliata. The sequence data indicate that Truncatella angustata was also associated with wood grapevine diseases in France; this species was previously reported on grapevine in Iran. The importance of controlling Pestalotioid fungi associated with wood grapevine diseases is discussed, which was previously considered of minor importance. These fungi are isolated from plants in nurseries before marketing. [ABSTRACT FROM AUTHOR]

Black foot disease, which is primarily caused by Dactylonectria species, affects young and mature grapevines, causing loss of productivity and reduction of longevity of vineyards. Because it is a soil-borne fungus, this pathogen offers limited control possibilities. This study aimed to assess the biocontrol activity of products based on Trichoderma spp. and Bacillus subtilis, in vitro and in vivo, against D. macrodidyma. In vitro assays were carried out to evaluate inhibition of mycelial growth of the pathogen through volatile metabolites and paired cultures assays. An in vivo experiment evaluated the potential biocontrol of the pathogen in plants of Vitis vinifera cv. Merlot, grafted on 'Paulsen 1103'. In the volatile metabolites assay, mean inhibition of mycelial growth in treatments using Trichoderma spp. was 59%. In the paired cultures experiment, treatment with B. subtilis (Rizolyptus®) gave 41% inhibition of the pathogen. In the in vivo assay, the best results for length of the primary shoots, total numbers of nodes and root dry weight were achieved with the B. subtilis treatments. This study demonstrates that B. subtilis has potential for biocontrol of D. macrodidyma. [ABSTRACT FROM AUTHOR]

Foliar symptoms of grapevine leaf stripe disease (GLSD, a disease within the esca complex) are linked to drastic alteration of photosynthetic function and activation of defense responses in affected grapevines several days before the appearance of the first visible symptoms on leaves. The present study suggests a methodology to investigate the relationships between high-resolution multispectral images (0.05 m/pixel) acquired using an Unmanned Aerial Vehicle (UAV), and GLSD foliar symptoms monitored by ground surveys. This approach showed high correlation between Normalized Differential Vegetation Index (NDVI) acquired by the UAV and GLSD symptoms, and discrimination between symptomatic from asymptomatic plants. High-resolution multispectral images were acquired during June and July of 2012 and 2013, in an experimental vineyard heavily affected by GLSD, located in Tuscany (Italy), where vines had been surveyed and mapped since 2003. Each vine was located with a global positioning system, and classified for appearance of foliar symptoms and disease severity at weekly intervals from the beginning of each season. Remote sensing and ground observation data were analyzed to promptly identify the early stages of disease, even before visual detection. This work suggests an innovative methodology for quantitative and qualitative analysis of spatial distribution of symptomatic plants. The system may also be used for exploring the physiological bases of GLSD, and predicting the onset of this disease. [ABSTRACT FROM AUTHOR]

The article presents abstracts on topics including the disease cycles of fungi associated with grapevine trunk diseases, diversity of Diatrypaceae species in three Spanish grapevine, and molecular diagnostic tool for detection of Botryosphaeriaceae species.

This study assessed the infection rates of different spore inoculum doses of the grapevine trunk pathogens Diplodia seriata, Phaeomoniella chlamydospora and Eutypa lata following artificial inoculation of pruning wounds. Potted vines of cv. Tempranillo were inoculated with doses ranging from 10 to 4000 conidia per wound of D. seriata and P. chlamydospora and led to recovery percentages of 10-100% for D. seriata and 16-94% for P. chlamydospora. Eutypa lata, when inoculated onto wounds of vines in a mature vineyard (cv. Shiraz) and on detached canes (cv. Cabernet Sauvignon) with a dose range of 10 to 1000 ascospores per wound, led to recovery percentages of 17-95%. In the field assay, there was no difference in recovery from wounds that were exposed to single or double inoculations with the same total spore dose, or between canes that were harvested 7 or 11 months after inoculation. The results obtained in this study showed significant variability in pathogen recovery between trials, comparable with that reported previously, which suggests that factors such as pathogen virulence, environmental parameters and experimental conditions may influence the infection process. According to this study, in order to obtain optimal recovery percentages of 50-70% for robust evaluation of pruning wound treatments, dose ranges of 100-1000 conidia of D. seriata, 100-2000 conidia of P. chlamydospora, and 100-500 ascospores of E. lata per wound would be required. [ABSTRACT FROM AUTHOR]

Togninia minima (anamorph Phaeoacremonium aleophilum) is one of the main fungi responsible for trunk diseases of grapevines and other woody hosts worldwide. Sequences of protein-coding genes of isolates from countries in different continents have been published, presenting a useful resource for examination of the diversity and spatial distribution of T. minima genotypes. Single nucleotide polymorphisms (SNPs) detected in public sequences of the actin and partial β-tubulin genes were used to assess the genetic variability and to determine haplotypes of isolates of this species from different sources. The Italian sample showed the greatest allele number and the largest number of haplotypes. Most haplotypes were present in more than one country, except for haplotype 11010 which was found only in Italy and 10111 found only in Canada. Haplotype 11111 was the most conspicuous and cosmopolitan, being present in six countries and on three host plant species. One observed polymorphism in the noncoding region of the β-tubulin gene could be targeted with allele-specific primers to detect this particular haplotype. [ABSTRACT FROM AUTHOR]

The Botryosphaeriaceae represents an important, cosmopolitan family of pathogens infecting woody plants. Grapevines (Vitis vinifera) suspected of being affected by Botryosphaeria dieback were collected from different Provinces of China and several Botryosphaeriaceae species were identified. This research was conducted to further study the species of Botryosphaeriaceae associated with grapevines in China and to estimate the prevalence and severity of the disease. Symptoms were characterized by partial or total death of grapevine cordons, with brown U-shaped necrotic sectors and brownish-black spots in cross-sections of affected trunks and arms. A fungus isolated from diseased vines in Henan and Anhui Provinces was identified as Neofusicoccum mangiferae on the basis of its morphological and cultural characteristics as well as an analysis of combined sequence data from the internal transcribed spacer (ITS) cluster of the ribosomal DNA together with partial sequences of the β-tubulin (BT) and translation elongation factor (EF1-α) genes. Pathogenicity was assessed by inoculating the fungus onto detached green grapevine shoots under controlled laboratory conditions and mature wood of standing vines cv. Summer Black in a greenhouse. This is the first record of N. mangiferae associated with grapevine dieback in the world. [ABSTRACT FROM AUTHOR]

Pleurostomophora richardsiae (Nannf. apud Melin & Nannf.) L. Mostert, W. Gams & Crous was previously known mainly as a human pathogen. However, more recently this fungus has been isolated from wood tissue of grapevines that show Petri and esca disease symptoms in California (USA) and South Africa. During an assessment carried out in southern Italy, the abundant presence of this fungus was demonstrated by morphological, cultural and molecular means. Pleurostomophora richardsiae was isolated from sub-cortical wood patches and streaking of trunks and cordons of grapevine cultivars that showed decline and dieback symptoms. To understand its putative pathogenic role, pathogenicity tests were conducted in greenhouse experiments, where young grapevine plants of two cultivars were artificially inoculated with two isolates each of Pl. richardsiae, Lasiodiplodia theobromae and Phaeoacremonium aleophilum. Within 130 d, all three fungi produced brown streaking in both grapevine cultivars. The L. theobromae and Pl. richardsiae isolates were the most aggressive. Although the Pm. aleophilum isolates were pathogenic, they induced less severe wood streaking than the other two fungi. Therefore, Pl. richardsiae is considered a fungal pathogen of grapevine. All three fungal species were re-isolated from discolored tissue of all inoculated shoots, thus fulfilling Koch's postulates. [ABSTRACT FROM AUTHOR]

Grapevine leaf stripe disease (GLSD) seriously reduces the quality and quantity of grape production, and results in a shorter lifespan of vineyards. Recent research has shown that foliar applications of nutrients influence the development of GLSD foliar symptoms. Based on this knowledge the effect of foliar applications of a mixture of calcium chloride, magnesium nitrate and Fucales seaweed extract on the development of leaf symptoms was evaluated over a 3-year period from 2010 to 2012. Nine foliar applications of the full mixture and its individual mineral components, also in different combinations, were tested in three different vineyards, one of cv. Trebbiano d'Abruzzo and two of cv. Montepulciano d'Abruzzo in the Teramo province (Abruzzo, Italy). Treatments were applied every 10 days from the beginning of vegetative growth to pre-bunch closure. The final results were similar in all the three vineyards and in the three years leading to a significant reduction of symptom development in the vines treated with the full mixture, while lower effects were obtained by applying partial combinations or single components. Both quantity and quality of grapes from the treated vines increased, while no phytotoxic or other unwanted effects on grape growth were detected. Vines treated with the full mixture showed an increase in trans-resveratrol and flavonoids content, and a higher accumulation of calcium oxalate in crystal druses in the leaf mesophyll. These data can be a useful base to set up a control strategy against GLSD and give some input for better understanding the mechanisms involved in foliar symptom expression in GLSD. [ABSTRACT FROM AUTHOR]