The best known Microdochium spp. are important pathogens of small-grain cereals and/or endophytes of diverse monocot hosts. This study is the first report of M. majus isolated from asymptomatic grapevine tissues. It was hypothesised that this M. majus strain, CBS 152328, was an endophyte and an antagonist of some fungal pathogens of grapevine. Microscopic examinations revealed that this strain was a necrotrophic mycoparasite of Botrytis cinerea. This was demonstrated in the confrontation zones of dual cultures of M. majus and B. cinerea, and also on the surface of co-inoculated grape leaf discs and germinated wheat grains. Pathogenicity tests indicated that M. majus can colonise both grape leaf discs and germinated wheat, but it only damaged wheat. When co-inoculated with B. cinerea onto grape leaf discs, the M. majus strain CBS 152328 suppressed its mycohost on grape tissues and prevented leaf necrosis caused by B. cinerea. In addition to the parasitism, M. majus also showed mild antibiosis against B. cinerea, as well as a defence elicitor effect on grape leaf discs. This work is the first report of the mycoparasitic behaviour of M. majus, in addition to its first isolation from a dicot host.

Several members of the fungal genus Ilyonectria primarily infect plants through the roots and basal stem, causing ‘black foot’ diseases, predominantly in woody plants such as grapevine ( Vitis spp.) and walnut ( Juglans regia ). In 2021, four Ilyonectria liriodendri isolates were cultured from the necrotized roots of Diospyros virginiana plants in Eger, Hungary. The isolates were identified by sequencing the ITS, β-tubulin, and partial histone H3 genes. The obtained sequences were used for phylogenetic analysis through multiple sequence alignment and the construction of a Maximum Likelihood tree, which revealed that all four isolates belonged to the species Ilyonectria liriodendri . The macro- and micromorphological variations, as well as the differences in exoenzyme production of the isolates suggested that they represent a somewhat diverse set of the same taxon. To prove their association with the symptoms observed in the host plants, the roots of one-year-old D. virginiana plants were artificially infected with conidial suspensions of the isolates according to Koch’s postulates. After 90 days of incubation in a greenhouse, 16 out of 20 inoculated plants showed necrosis in the taproots, while mock-inoculated plants remained symptomless. Necroses developed in the roots of the infected plants, and the inoculated fungi were reisolated, reinforcing their pathogenicity against D. virginiana . To the best of our knowledge, this is the first report of I. liriodendri causing disease in persimmon.

The present study is the first observation of mycoparasitic behavior in the predominantly plant-associated fungal genus Diaporthe . Several isolates of the Phomopsis dieback pathogen Diaporthe eres s.l. were obtained from grapevine and identified by sequencing the internal transcribed spacer, translation elongation factor 1-α, and β-tubulin loci. The interactions of the isolates with Botrytis cinerea strains were examined by detailed microscopic analysis. All the tested isolates showed necrotrophic mycoparasitism against the target organism. Additional experiments with a D. eres s.l. isolate showed that mycoparasitism was also expressed against a Botryosphaeria dothidea target organism, a causal agent of Botryosphaeria dieback, another grapevine trunk disease syndrome. In addition to the first description of the mycoparasitism of D. eres , the study points out the complexity of microbial interactions established by trunk disease pathogens.

The present study suggests that the Esca pathogenic fungus Phaeomoniella chlamydospora can form biofilm in vitro and possibly in the grapevine host tissues. This phenomenon was revealed by the detailed examination of the development of three isolates of the fungus, showing dimorphic growth with the formation of yeast-like cells in the center, which were embedded in a polysaccharide-rich extracellular matrix, and filamentous growth at the colony margins. The colonies produced acetate, which chemical proved to be an enhancer of yeast-like growth and extracellular matrix production. The dynamic of biofilm formation was correlated with the ability of the strains to produce acetate, suggesting that it acts as a quorum sensing molecule in the process. The dimorphic growth of P. chlamydospora was also demonstrated in host tissues as a sole nutrient source, suggesting that biofilm can be produced in planta and take part in the pathogenesis of Esca. The biofilms formed by the fungus may contribute to the previously reported inhibition of sap flow in the infected plants, while its quorum sensing-mediated nature may partly explain the controversial literature data on the occurrence of the pathogen and symptom severity in the host.

One of the major and yet unsolved threats for viticulture is the group of vascular fungal infections, the so-called grapevine trunk diseases. Besides their latent nature and the enormous number of associated pathogens, their control is also hampered by the lack of effective fungicides, directing growing attention toward the use of biocontrol agents. In the present study the isolation, identification, and characterization of a bacterial strain are presented, showing biocontrol potential against some main causal agents of grapevine trunk diseases. The strain was isolated from the wood of an asymptomatic grapevine and selected for the fungicidal activity against the pathogen Phaeomoniella chlamydospora. According to 16S rDNA, gyrA, and gyrB sequences, the isolate belongs to Bacillus velezensis species. Confrontation tests with the bacterium or with its fermentation broth further revealed growth inhibition and fungicide activity against Botryosphaeria dothidea, Eutypa lata and Diaporthe ampelina pathogens. Fractionation of the bacterial culture filtrate suggests that the antifungal agents secreted by the B. velezenzis isolate are mainly lipoproteins. Phytotoxicity tests were also carried out with the isolate, showing no harmful effects on grapevine foliar disks.

Phaeomoniella chlamydospora (Pch) is a pioneer pathogen of esca, one of the most destructive grapevine trunk diseases worldwide. A recent work suggests that acetate may act as a quorum-sensing (QS) molecule in Pch, promoting biofilm formation in a concentration-dependent manner. However, the broader influence of acetate on virulence-associated traits remains unexplored. In this study, three Pch isolates were cultured under increasing sodium acetate concentrations (0–100 mM) and assessed for pigmentation, extracellular enzyme activities (amylase, cellulase, protease, esterase, and pectinase), phenolic compound-degrading capacity, and antibacterial activity against a grapevine-associated Pseudomonas sp. isolate. Pigmentation, as well as amylase and cellulase activities, were significantly increased at low acetate supplement levels (6.25–12.5 mM), while esterase activity was unaffected. The expression of these traits decreased above 25 mM acetate supplementation. Phenolic compound degradation capacity, antibacterial efficacy, as well as protease and pectinase activities progressively suppressed at all acetate concentrations. These results indicate that acetate concentration modulates multiple virulence-associated phenotypes of Pch in vitro. Based on these patterns, we propose a hypothetical model in which acetate-dependent phenotypic changes may reflect a shift between establishment-associated activities and reduced extracellular activity at higher acetate levels. This model remains to be validated by mechanistic and in planta infection-based studies.