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Previous works on grapevine-trunk diseases indicate that minimal or non-pruning of the grapevine under certain circumstances can significantly reduce the risk of symptom expression. Nevertheless, knowledge of the mechanisms behind these observations are limited. Therefore, it was the aim of this study to investigate in more detail the effect of pruning intensity on the grapevine trunk by means of trunk integrity and the fungal community in the wood tissue. Two German vineyards partially trained in vertical-shoot position and semi-minimally pruned hedges were chosen for this survey due to the accessibility of multi-annual esca-monitoring data. The results revealed that only in one of the two vineyards was the incidence of external esca symptoms significantly reduced over a period of five years (2017–2021) by minimal pruning, which was up to 73.7% compared to intensive pruning. In both vineyards, the trunks of intensively pruned vines not only had more pruning wounds on the trunk (by 86.0% and 72.9%, respectively) than minimally pruned vines, but also exhibited a larger (by 19.3% and 14.7%, respectively) circumference of the trunk head. In addition, the percentage of white rot and necrosis in the trunks of esca-positive and esca-negative vines was analyzed and compared between the two pruning intensities; hereby, significant differences were only found for esca-negative ‘Dornfelder’ vines, in which the proportion of necrosis was higher for intensively pruned vines (23.0%) than for minimally pruned vines (11.5%). The fungal communities of the differently pruned vine trunks were mainly dominated by four genera, which are also associated with GTDs: Diplodia, Eutypa, Fomitiporia and Phaeomoniella. All in all, the fungal diversity and community composition did not differ between minimally and intensively pruned, esca-positive vines.

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Strains with a yeast-like appearance were frequently collected in two surveys on the biodiversity of fungi in Germany, either associated with necroses in wood of Prunus trees in orchards in Saxony, Lower Saxony and Baden-Württemberg or captured in spore traps mounted on grapevine shoots in a vineyard in Rhineland-Palatinate. The morphology of the strains was reminiscent of the genus Collophorina: all strains produced aseptate conidia on integrated conidiogenous cells directly on hyphae, on discrete phialides, adelophialides and by microcyclic conidiation, while in some strains additionally endoconidia or conidia in conidiomata were observed. Blastn searches with the ITS region placed the strains in the Leotiomycetes close to Collophorina spp. Analyses based on morphological and multi-locus sequence data (LSU, ITS, EF-1α, GAPDH) revealed that the 152 isolates from wood of Prunus spp. belong to five species including C. paarla, C. africana and three new species. A further ten isolates from spore traps belonged to seven new species, of which one was isolated from Prunus wood as well. However, a comparison with both LSU and ITS sequence data of these collophorina-like species with reference sequences from further Leotiomycetes revealed the genus Collophorina to be polyphyletic and the strains to pertain to several genera within the Phacidiales. Collophorina paarla and C. euphorbiae are transferred to the newly erected genera Pallidophorina and Ramoconidiophora, respectively. The new genera Capturomyces, Variabilispora and Vexillomyces are erected to accommodate five new species isolated from spore traps. In total nine species were recognised as new to science and described as Collophorina badensis, C. germanica, C. neorubra, Capturomyces funiculosus, Ca. luteus, Tympanis inflata, Variabilispora flava, Vexillomyces palatinus and V. verruculosus.