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Esca is a grapevine trunk disease (GTD) that is caused by filamentous fungi. It is responsible for considerable economic losses in viniculture on a global scale. Despite many unknown factors contributing to the development of symptoms in affected plants, Phaeoacremonium minimum (PMI), Phaeomoniella chlamydospora (PCH) and Fomitiporia mediterranea (FMED) are generally considered as the main causative fungal species. Early detection and specific identification of these pathogens therefore play an important role in disease control and evaluation of suitable countermeasures. In this study, loop‐mediated isothermal amplification (LAMP) assays were developed for each of the three pathogens. A genome‐based approach was applied for detection and selection of unique target DNA sequences. The designed primer sets showed overall good specificities, with some observed cross‐reactions towards closely related Phaeoacremonium species for the PMI primer set. The developed assays had detection limits of 100 pg (FMED, PMI) and 1 pg (PCH) per reaction (corresponding to 1460 [FMED]; 1950 [PMI]; 342 [PCH] genome copies per reaction). The application of the assays to field samples was demonstrated by testing individual infected grapevine trunks from two European viticultural regions using crude DNA obtained in a rapid sample preparation step. LAMP assay results matched those of PCR following a conventional DNA extraction protocol. The study showed that LAMP‐based rapid molecular detection of major Esca agents can serve as a useful tool for further research and surveillance of a highly devastating grapevine disease. The application of computer‐based whole genome comparison between target and non‐target species for the identification of unique target sequences as the basis for LAMP (or PCR) primer design was demonstrated to be a useful approach in species for which scarce sequence information is available. Moreover, the developed method for rapid DNA preparation from grapevine trunks may potentially be adapted to the DNA‐based detection also of other fungal species that cause grapevine trunk diseases. [ABSTRACT FROM AUTHOR]

BACKGROUND: Copper‐containing fungicides are applied broadly in organic viticulture against downy mildew caused by Plasmopara viticola. Although long‐term application of copper‐based fungicides is associated with ecotoxic effects on the environment, their use in viticulture is required until sustainable alternatives are available. Trichoderma spp. might be a promising approach to fungicide reduction while promoting plant growth and development and displaying biocontrol activity. This study aims to examine the tolerance and compatibility of Trichoderma spp. to copper fungicides. This work contributes to the development of a spray application consisting of a copper‐tolerant Trichoderma sp. combined with a downscaled copper fungicide rate against P. viticola. RESULTS: Trichoderma spp. isolated from grapevine wood in vineyards were identified and used for tolerance screening in various concentrations of copper fungicides. Copper hydroxide was identified as being highly compatible with Trichoderma. Two Trichoderma candidates, T. koningiopsis and T. harzianum, showed high copper tolerance in mycelial growth and germination tests, and were adapted to 2.85 g Cu L−1 of the selected fungicide. Microscopic investigations showed the attachment of copper compounds to fungal cell walls and copper uptake within the cytoplasm. In the case of high tolerance, large‐scale copper uptake was prevented. CONCLUSION: Our findings identified two highly copper‐tolerant Trichoderma isolates with natural adaptation to the vineyard ecosystem, which could be further tested as biostimulants and biocontrol agents, combined with a reduced fungicide rate for sustainable plant protection. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Grapevine (Vitis vinifera ssp. vinifera) is one of the most important fruit species; however, it is highly susceptible to various pathogens, which can cause severe crop losses in viticulture. It has been shown that several WRKY class transcription factors (TFs) are part of the signal transduction cascade, which leads to the activation of plant defense reactions against various pathogens. In the present investigation, a full‐length cDNA was isolated from V. vinifera leaf tissue encoding a predicted protein, designated VvWRKY33, which shows the characteristics of group I WRKY protein family. VvWRKY33 induction correlates with the expression of VvPR10.1 (pathogenesis‐related 10.1) gene in the leaves of the resistant cultivar ‘Regent’ after infection with Plasmopara viticola, whereas in the susceptible cultivar ‘Lemberger’ VvWRKY33 and VvPR10.1 are not induced. Corresponding expression of the TF and VvPR10.1 was even obtained in uninfected ripening berries. In planta, analysis of VvWRKY33 has been performed by ectopic expression of VvWRKY33 in grapevine leaves of greenhouse plants mediated via Agrobacterium tumefaciens transformation. In consequence, VvWRKY33 strongly increases resistance to P. viticola in the susceptible cultivar ‘Shiraz’ and reduces pathogen sporulation of about 50–70%, indicating a functional role for resistance in grapevine. Complementation of the resistance‐deficient Arabidopsis thaliana Columbia‐0 (Col‐0) mutant line wrky33‐1 by constitutive expression of VvWRKY33 restores resistance against Botrytis cinerea to wild‐type level and in some complemented mutant lines even exceeds the resistance level of the parental line Col‐0. Our results support the involvement of VvWRKY33 in the defense reaction of grapevine against different pathogens. [ABSTRACT FROM AUTHOR]