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Phaeomoniella chlamydospora (Pch) is one of the main pathogens causing Petri disease, a grapevine trunk disease responsible for the decline and mortality of grapevines within a few years after planting. Phaeomoniella chlamydospora has been shown to be prevalent in asymptomatic grapevine nursery material, leading to the hypothesis that it may act as a latent pathogen, transitioning from an endophytic to a pathogenic phase under grapevine stress. To investigate this hypothesis, a two-year greenhouse and a four-year field experiment were conducted on young self-rooted ‘Merlot’, and ‘Merlot’ grafted onto ‘SO4’ rootstock, artificially inoculated with different spore concentrations of Pch and subjected to water stress. Additionally, the arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis was inoculated in the soil in the greenhouse experiment to investigate its effects on abiotic stress mitigation and thus, disease development in water stressed and non-stressed grapevines. DNA was extracted from the grapevine wood, and Droplet Digital™ PCR was conducted to determine Pch abundance before and after the experiments. In the greenhouse, Pch abundance in inoculated grapevines was greater in water stressed grapevines treated with AM than in stressed grapevines without AM or in non-stressed grapevines. Basal necrosis was greater in grapevines inoculated with Pch. In the field, Pch abundance was not affected by water stress, but basal necrosis was greater in grapevines inoculated with a high spore concentration of the fungus. Symptoms resembling Petri disease developed in the third year of the field experiment, where water stress increased grapevine mortality. This study shows that water stress may increase Pch abundance and mortality in young grapevines within the first few years after planting.

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.

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]

Wine grape production is an important economic asset in many nations; however, a significant proportion of vines succumb to grapevine trunk pathogens, reducing yields and causing economic losses. Cover crops, plants that are grown in addition to main crops in order to maintain and enhance soil composition, may also serve as a line of defense against these fungal pathogens by producing volatile root exudates and/or harboring suppressive microbes. We tested whether cover crop diversity reduced disease symptoms and pathogen abundance. In two greenhouse experiments, we inoculated soil with a 106 conidia suspension of Ilyonectria liriodendri, a pathogenic fungus, then conditioned soil with cover crops for several months to investigate changes in pathogen abundance and fungal communities. After removal of cover crops, Chardonnay cuttings were grown in the same soil to assess disease symptoms. When grown alone, white mustard was the only cover crop associated with reductions in necrotic root damage and abundance of Ilyonectria. The suppressive effects of white mustard largely disappeared when paired with other cover crops. In this study, plant identity was more important than diversity when controlling for fungal pathogens in vineyards. This research aligns with other literature describing the suppressive potential of white mustard in vineyards.

Young vine decline (YVD), caused by several taxonomically different fungi, results in the decline and death of grapevines within a few years after planting. Infection can occur in nursery mother blocks and/or at several stages in the nursery propagation process, but the final plant material may remain asymptomatic. Four nurseries that sell ready-to-plant grapevines in Canada were sampled to evaluate the health status with regard to YVD fungi, including Botryosphaeriaceae spp., Cadophora luteo-olivacea , Dactylonectria macrodidyma , Dactylonectria torresensis , Phaeoacremonium minimum , and Phaeomoniella chlamydospora . Plants representing three cultivars, 'Chardonnay', 'Merlot', and 'Pinot noir', either grafted onto '3309C' rootstock or self-rooted, were provided by the nurseries. Samples from the roots, base of the rootstock or self-rooted cultivar, graft-union, and scion were collected from each plant. DNA was extracted, and the total abundance of each fungus was quantified using Droplet Digital PCR. Results revealed that 99% of plants harbored at least one of the fungi studied, with a mean of three different fungal species that were present per grapevine. Droplet Digital PCR results showed that the abundance of the different fungi significantly varied between different sections of each plant, individual plants for each cultivar, and cultivars from the same nursery. Necrosis measurements were recorded from the base of the rootstock or self-rooted cultivars and did not correlate with fungal abundance recorded in that section for each grapevine, but necrosis was consistent across cultivars within nurseries. Five different rootstocks were compared from one nursery, and results showed no differences between rootstocks and their health status. Among all nurseries, C. luteo-olivacea was the most prevalent fungus (97% of the plants), while D. macrodidyma was the least commonly found (13% of the plants). This study shows that ready-to-plant nursery material sold in Canada is likely to be infected with several YVD fungi and that presence and abundance of fungi vary significantly among individual grapevines and nurseries., Competing Interests: The author(s) declare no conflict of interest.

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]

A questionnaire covering all aspects of grapevine propagation including cultural and sanitation practices in mother blocks and harvest and transport of cuttings from mother blocks to nurseries, nursery operations and field nursery management, was mailed to all Management Committee members of the European COST Action FA1303 “Sustainable Control of Grapevine Trunk Diseases” for distribution to the identifiable nurseries in each European country. The main objective was to develop understanding of the current propagation practices and to identify those likely to have the greatest impacts on the quality of planting material, especially with regard to the control measures used against fungal trunk pathogen infections. The questionnaire was sent to 666 vine nurseries, and 146 replies were received (21.9% response rate) The study identified several risks factors which could increase infection by fungal trunk pathogens during the propagation processes, as well as a clear need for further research into the effects of treatments on grapevine viability, including hot water treatment, and the potential of biological agents and other strategies such as ozonation to control grapevine trunk diseases in nurseries.

A questionnaire covering all aspects of grapevine propagation including cultural and sanitation practices in mother blocks and harvest and transport of cuttings from mother blocks to nurseries, nursery operations and field nursery management, was mailed to all Management Committee members of the European COST Action FA1303 "Sustainable Control of Grapevine Trunk Diseases" for distribution to the identifiable nurseries in each European country. The main objective was to develop understanding of the current propagation practices and to identify those likely to have the greatest impacts on the quality of planting material, especially with regard to the control measures used against fungal trunk pathogen infections. The questionnaire was sent to 666 vine nurseries, and 146 replies were received (21.9% response rate) The study identified several risks factors which could increase infection by fungal trunk pathogens during the propagation processes, as well as a clear need for further research into the effects of treatments on grapevine viability, including hot water treatment, and the potential of biological agents and other strategies such as ozonation to control grapevine trunk diseases in nurseries. [ABSTRACT FROM AUTHOR]

Sporadic and costly failure of newly planted vines is an ongoing problem in the Australian wine industry. Failed vines are frequently infected with wood pathogens, including the fungi associated with Young Vine Decline. Hot water treatment (HWT) and other nursery practices have also been implicated in vine failure. We undertook a survey of Australian grapevine nurseries to develop an understanding of current propagation practices and to facilitate the development of reliable propagation procedures that consistently produce high quality vines. A survey covering all aspects of grapevine propagation including sources of cuttings, HWT, sanitation and cold storage was mailed to all 60 trading Australian vine nurseries. In all, 25 nurseries responded, a response rate of 41.7%. Practices were found to vary widely both within and between nurseries. The vast majority of respondents (20) reported that they currently used, or had used, HWT, but the reliability of HWT was questioned by most nursery operators. A majority (18) felt that some Vitis vinifera varieties were more sensitive to HWT than others. Hydration also emerged as an important factor that had the potential to affect vine quality. All respondents used hydration and although the majority used treated water, cuttings were not generally seen as a source of cross contamination. Our study identified a clear need for further research into the effects of HWT on cutting physiology and the role of hydration in the epidemiology of grapevine pathogens, and the importance of incorporating the results of such research into practical and comprehensive propagation guidelines for vine nurseries.

Sporadic and costly failure of newly planted vines is an ongoing problem in the Australian wine industry. Failed vines are frequently infected with wood pathogens, including the fungi associated with Young Vine Decline. Hot water treatment (HWT) and other nursery practices have also been implicated in vine failure. We undertook a survey of Australian grapevine nurseries to develop an understanding of current propagation practices and to facilitate the development of reliable propagation procedures that consistently produce high quality vines. A survey covering all aspects of grapevine propagation including sources of cuttings, HWT, sanitation and cold storage was mailed to all 60 trading Australian vine nurseries. In all, 25 nurseries responded, a response rate of 41.7%. Practices were found to vary widely both within and between nurseries. The vast majority of respondents (20) reported that they currently used, or had used, HWT, but the reliability of HWT was questioned by most nursery operators. A majority (18) felt that some Vitis vinifera varieties were more sensitive to HWT than others. Hydration also emerged as an important factor that had the potential to affect vine quality. All respondents used hydration and although the majority used treated water, cuttings were not generally seen as a source of cross contamination. Our study identified a clear need for further research into the effects of HWT on cutting physiology and the role of hydration in the epidemiology of grapevine pathogens, and the importance of incorporating the results of such research into practical and comprehensive propagation guidelines for vine nurseries. [ABSTRACT FROM AUTHOR]

Wine grape production is an important economic asset in many nations; however, a significant proportion of vines succumb to grapevine trunk pathogens, reducing yields and causing economic losses. Cover crops, plants that are grown in addition to main crops in order to maintain and enhance soil composition, may also serve as a line of defense against these fungal pathogens by producing volatile root exudates and/or harboring suppressive microbes. We tested whether cover crop diversity reduced disease symptoms and pathogen abundance. In two greenhouse experiments, we inoculated soil with a 106 conidia suspension of Ilyonectria liriodendri, a pathogenic fungus, then conditioned soil with cover crops for several months to investigate changes in pathogen abundance and fungal communities. After removal of cover crops, Chardonnay cuttings were grown in the same soil to assess disease symptoms. When grown alone, white mustard was the only cover crop associated with reductions in necrotic root damage and abundance of Ilyonectria. The suppressive effects of white mustard largely disappeared when paired with other cover crops. In this study, plant identity was more important than diversity when controlling for fungal pathogens in vineyards. This research aligns with other literature describing the suppressive potential of white mustard in vineyards. [ABSTRACT FROM AUTHOR]