Fusarium species are agriculturally important fungi with a broad host range and can be found as endophytic, pathogenic, or opportunistic parasites in many crop plants. This study aimed to identify Fusarium species in bare-rooted, dormant plants in Turkish grapevine nurseries using molecular identification methods and assess their pathogenicity. Asymptomatic dormant plants were sampled from grapevine nurseries (43) in different regions of the country, and fungi were isolated from plant roots and internal basal tissues. The Fusarium strains were identified by performing gene sequencing (TEF1-α, RPB2) and phylogenetic analyses. Pathogenicity tests were carried out by inoculating mycelial agar pieces of strains onto the stem or conidial suspensions into the rhizosphere of vines (1103 Paulsen rootstock). Laboratory tests revealed that Fusarium species were highly prevalent in Turkish grapevine nurseries (41 out of 43). Gene sequencing and phylogenetic analyses unraveled that 12 Fusarium species (F. annulatum, F. brachygibbosum, F. clavum, F. curvatum, F. falciforme, F. fredkrugeri, F. glycines, F. nanum, F. nematophilum, F. nirenbergiae, F. solani, and Fusarium spp.) existed in the ready-to-sale plants. Some of these species (F. annulatum, F. curvatum and F. nirenbergiae) consistently caused wood necrosis of seedling stems, rotting of the basal zone and roots, and reduced root biomass. Although the other nine species also caused some root rot and root reduction, their virulence was not as severe as the pathogenic ones, and they were considered opportunistic parasites or endophytic species. This study suggests that Fusarium species might play an important role in root-basal rot, wood canker symptoms, and young vine decline in Turkish grapevine nurseries and that these species need to be considered for healthy seedling production.

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.

Fusarium species are agriculturally important fungi with a broad host range and can be found as endophytic, pathogenic, or opportunistic parasites in many crop plants. This study aimed to identify Fusarium species in bare-rooted, dormant plants in Turkish grapevine nurseries using molecular identification methods and assess their pathogenicity. Asymptomatic dormant plants were sampled from grapevine nurseries (43) in different regions of the country, and fungi were isolated from plant roots and internal basal tissues. The Fusarium isolates were identified by performing gene sequencing (TEF1-α, RPB2) and phylogenetic analyses. Pathogenicity tests were carried out by inoculating mycelial agar pieces of isolates onto the stem or conidial suspensions into the rhizosphere of vines (1103 Paulsen rootstock). Laboratory tests revealed that Fusarium species were highly prevalent in Turkish grapevine nurseries (41 out of 43). Gene sequencing and phylogenetic analyses unraveled that 12 Fusarium species (F. annulatum, F. brachygibbosum, F. clavum, F. curvatum, F. falciforme, F. fredkrugeri, F. glycines, F. nanum, F. nematophilum, F. nirenbergiae, F. solani, and Fusarium spp.) existed in the ready-to-sale plants. Some of these species (F. annulatum, F. curvatum and F. nirenbergiae) consistently caused wood necrosis of seedling stems, rotting of the basal zone and roots, and reduced root biomass. Although the other nine species also caused some root rot and root reduction, their virulence was not as severe as the pathogenic ones, and they were considered opportunistic parasites or endophytic species. This study is the first detailed investigation of Fusarium species in grapevine nurseries in Türkiye and emphasizes the need to consider pathogenic species in producing healthy grapevine seedlings.

This research aimed to determine abilities of endophytic Aspergillus, Penicillium, and Trichoderma species to colonize grapevine cuttings, and to evaluate their performance for protecting pruning wounds from Botryosphaeriaceae fungi under greenhouse and field conditions. Colonization ability of five endophytic species (Aspergillus allahabadi, A. flavipes, Penicillium canescens, P. fructuariae-cellae, and Trichoderma brevicompactum) was assessed after introductions into cuttings using two inoculation methods: immersion in conidial suspensions or contact with dry conidia. Colonization by the inoculated fungi was subsequently confirmed through re-isolations, and species identities were verified by PCR and gene sequencing. After confirming colonization, biological activity of the endophytes was assessed against pathogens. Conidium suspensions were either sprayed onto host wounds or applied systemically to cuttings, and necrotic lengths in internal tissues were measured 4 months after inoculations. In a subsequent field experiment, conidium suspensions were applied by spraying onto pruning wounds, or placing mycelium/agar plugs, and extent of necroses was assessed 6 months after inoculations. Penicillium and Trichoderma species colonized internal tissues of grapevine plants, whereas Aspergillus species were not re-isolated. In greenhouse trials, the endophytes reduced lesion lengths caused by Botryosphaeriaceae species by 22 to 85 %. Under field conditions, and where applied to pruning wounds, these fungi gave 51 to 70% protection against Lasiodiplodia brasiliensis and Neofusicoccum parvum, with Trichoderma brevicompactum giving greatest efficacy. This study has shown that vineyard-derived Penicillium and Trichoderma endophytes can establish within grapevine tissues, and have potential to effectively suppress Botryosphaeriaceae pathogens of grapevines.