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Climate change is driving the emergence of novel tree diseases at the global scale, requiring new approaches for the formal confirmation of the pathogenicity of novel pathogens on novel hosts. At the same time, predictive models need to account for the possible effect of environmental changes and of abiotic stressors on disease severity for all diseases. By wound-inoculating Botryosphaeria dothidea on potted California coast live oaks and Cryptostroma corticale on potted silver maples, simultaneously in well-watered and in water-deprived conditions, I show that drought conditions increase the severity of disease symptoms. I also show that, by including a water-stressed treatment, I can formally prove pathogenicity and fulfill Koch’s postulates for putative pathogens that could not be confirmed in the absence of the stressor. Additionally, I show that the inclusion of data obtained in water stress conditions increases the differentiation between symptoms caused by fungal infection vs. symptoms caused by wound trauma, thus reducing the possible effect of outliers, a significant problem affecting many trials for fulfilling Koch’s postulates conducted with a limited number of replicates. The availability of comparable datasets in the presence and the absence of an abiotic stressor allows for the calculation of an Environmental Disease Component Index. Positive values of the index indicate a significant role of environmental change in disease progression and identify those pathogens that must be modeled factoring in climatic stressors. I suggest that this index may be extremely valuable for identifying pathogens likely to become emergent as climate changes.

AIM : Cryptic species in the Neofusicoccum parvum–N. ribis species complex have only recently been described, invalidating previous interpretations on host and geographical distribution. This study aimed to characterize the diversity and distribution of these species and to understand the patterns of host associ- ation, likely origins and their patterns of spread. LOCATION : Australia, Brazil, Cameroon, Chile, China, Colombia, Ethiopia, France, Greece, India, Indonesia, Iran, Italy, Japan, Kenya, Mexico, New Zealand, Panama, Portugal, Puerto Rico, South Africa, South Korea, Spain, Swaziland, Taiwan, Thailand, Uganda, United States of America, Uruguay, Zambia and Zimbabwe. METHODS : Using the unique polymorphisms that separate species within the complex, we evaluated sequence search results available in public and in our own databases. In addition, the global distribution of diversity of N. parvum was analysed using seven microsatellite markers. RESULTS : Neofusicoccum parvum is found in 90 hosts across six continents and 29 countries. Neofusicoccum kwambonambiense is found on four continents, six countries and on 14 hosts; N. occulatum is found on four continents, four countries and on 11 hosts; N. umdonicola is found on two continents, countries and hosts; N. cordaticola is found on three continents, countries and hosts; N. batangarum is found on two continents, three countries and three hosts; and N. ribis is found on one host in one country. Population genetic analysis of the global N. parvum population reflects admixture and repeat introductions. MAIN CONCLUSIONS : This study illustrates the unfettered and frequent movement of latent pathogens across international borders. Amongst the species in the N. parvum–N. ribis complex, N. parvum is the most widespread and has been reported on the majority of the hosts studied. The current dispersal of N. par- vum and its sister species is probably due to repeated introductions of plant material into new growing areas, with Eucalyptus and Vitis vinifera being two prominent candidates for material transfer.

Fungi in the Botryosphaeriaceae are important plant pathogens that persist endophytically in infected plant hosts. Lasiodiplodia theobromae is a prominent species in this family that infects numerous plants in tropical and subtropical areas. We characterized a collection of 255 isolates of L. theobromae from 52 plants and from many parts of the world to determine the global genetic structure and a possible origin of the fungus using sequence data from four nuclear loci. One to two dominant haplotypes emerged across all loci, none of which could be associated with geography or host; and no other population structure or subdivision was observed. The data also did not reveal a clear region of origin of the fungus. This global collection of L. theobromae thus appears to constitute a highly connected population. The most likely explanation for this is the human-mediated movement of plant material infected by this fungus over a long period of time. These data, together with related studies on other Botryosphaeriaceae, highlight the inability of quarantine systems to reduce the spread of pathogens with a prolonged latent phase.

The complex of spaceflight factors has a significant impact on the immunity functional activity. This influence is probably caused by factors such as isolation, monotony, physical inactivity, sensory deprivation, and increased psycho-emotional tension. Long-term wintering at polar stations can be the ground-based model that is most similar to space flight conditions. This research focused on examining the reactivation of latent human pathogens among 11 participants of the 64th Russian Antarctic expedition to Vostok station. Plasma, saliva and urine samples collected before arriving at the station and also during the wintering were studied. Even at the pre-expedition period, DNA of at least one of the studied pathogens was detected in the saliva and plasma of 10 out of 11 (90%) expedition members. During the wintering all the participants showed changes in the Epstein-Barr virus DNA concentration in body fluids. Moreover, 9 out of 11 (80%) participants showed the human herpes virus type 6 shedding in the saliva and/or plasma. Herpes simplex virus types 1 and 2 shedding was observed in 18% of subjects as well. Additionally, there was an assumption made about the relationship between dynamics of latent pathogen shedding, geomagnetic activity, and the psychological state of expedition participants.

Many fungi reported for endophytic occurrence are better known as plant pathogens on different crops, raising questions about their actual relationships with the hosts and other plants in the biocoenosis and about the factors underlying the lifestyle shift. This paper offers an overview of the endophytic occurrence of Lasiodiplodia theobromae (Dothideomycetes, Botryosphaeriaceae), a species known to be able to colonize many plants as both an endophyte and a pathogen. Prevalently spread in tropical and subtropical areas, there are concerns that it may propagate to the temperate region following global warming and the increasing trade of plant materials. The state of the art concerning the biochemical properties of endophytic strains of this species is also examined with reference to a range of biotechnological applications.

The development and validation of a real-time PCR method for the detection of Cryphonectria parasitica in bark tissues is described. The selected region in the genome was a fragment of the internal transcribed spacer region. The DNA extraction and PCR conditions were optimized to be routinely applicable to fresh and dried bark. The sensitivity of the assay allowed the detection of 2 fg of genomic DNA, equivalent to one spore of the pathogen. There was no cross-reaction with closely related Cryphonectria species. The use of droplet digital PCR (ddPCR) confirmed the high sensitivity of the real-time PCR method, and its capacity to be used as an early detection method. A survey was conducted in Belgium on chestnut trees displaying cankers using isolation and the real-time PCR method. Both methods provided the same results for 83% of the samples (either negative or positive results). For the remaining samples, C. parasitica was not isolated, while amplifications close to the end of the PCR run (resulting in late Cycle threshold (Ct) values) were observed with the real-time PCR. Some of these samples were collected in stands where C. parasitica had already been detected on other chestnut trees, or in sites close to the infected stands. The application of this method may help plant protection services to detect new introductions of the pathogen within areas still free of chestnut blight and to prevent its establishment. It may also be useful for scientists involved in the epidemiology of the disease.

Biscogniauxia nummularia is a xylariaceous fungus known as a common endophyte of European beech, living in plant tissues without development of symptoms, or even inducing strip-cankers and wood decay on trees stressed by drought. We studied the presence of the fungus in apparently healthy beech trees, growing in two different bioclimatic zones characterized by Continental and Mediterranean climates. Asymptomatic twigs were collected in each zone over the season and evaluated for the presence of B. nummularia infections using both cultural and qPCR methods. Results from qPCR indicated differences in the detection of B. nummularia among the seasons and between the study sites. In both sites the highest frequency of detection was in summer. B. nummularia was more frequently detected in the Mediterranean bioclimatic area, where drought is more common. These results suggest that B. nummularia may be a possible bioindicator of beech health stands.

This study investigated the composition and temporal dynamics of wood-inhabiting fungal communities in four aging tree species in Lednice Castle Park (Czech Republic), located within the Lednice–Valtice Cultural Landscape, a UNESCO World Heritage Site. Forty wood cores were collected from 20 trees at two time points (2023 and 2024). The hosts included horse chestnut (Aesculus hippocastanum L.), copper beech (Fagus sylvatica ‘Atropunicea’ L.), oak (Quercus robur L.), and poplar (Populus alba L.), each exhibiting visual signs of decline. Fungal assemblages were profiled using ITS2 high-throughput amplicon sequencing. Ascomycota dominated across all hosts (72–89% of reads), while Basidiomycota contributed 8–24%, largely represented by Agaricomycetes in F. sylvatica. Alpha diversity varied significantly among hosts (Shannon: F3,36 = 10.61, p = 0.001 in 2023; F3,36 = 10.00, p = 0.001 in 2024). Temporal shifts were host-dependent: F. sylvatica exhibited the strongest year-to-year decline in richness (Chao1: −83%, p = 0.007) and increased beta dispersion, while A. hippocastanum and P. alba showed significant increases in diversity (+65% and +42%, respectively). Community composition was shaped by host species (PERMANOVA Bray–Curtis: p = 0.001) and shifted over time (Jaccard: p = 0.001), with F. sylvatica showing the highest temporal turnover. Functional guild analysis revealed consistent dominance of saprotrophs (29–41%) and mixed pathotroph–saprotroph guilds (23–36%) across hosts, indicating active degradation processes inside functional xylem. These results indicate that, within the studied system, the wood mycobiome of aging trees is host-dependent and temporally dynamic rather than static or functionally neutral. Short-term temporal turnover observed between sampling years may contribute to shifts in fungal community composition and succession within wood, with potential implications for tree decline processes in managed historical park landscapes.

Occurrence of genus Fusarium as endophytes in roots of healthy barley plants cultivated in fields under two levels of phosphorous (P) was examined. F. avenaceum, F. graminearum, F. konzum, F. oxysporum, F. sacchari, F. scirpi, F. solani were isolated from asymptomatic surface sterilized root tissues. F. konzum and F. solani were only present in the roots of fertilized plants, whereas F. sacchari was present in unfertilized plants. F. scirpi was isolated in highest frequency and relative density, and was higher under P deficiency suggesting that P availability would determinate the occurrence of this species, suggesting the possibility of their association with stressed plants. This is the first report on the occurrence of Fusarium spp. as endophytes in healthy barley plants. However, it remains to be determined whether Fusarium spp. isolated are nonpathogenic forms and beneficial to barley plants or latent pathogens that could produce disease symptoms in other conditions.

Latent pathogenic fungi (LPFs) affect plant growth, but some of them may stably colonize plants. LPFs were isolated from healthy rhizomes to reveal this mechanism and identified as , an unidentified fungal sp., and . Sterile seedlings were cultivated in sterile or non-sterile soils and inoculated with the LPFs, followed by the plants’ analysis. The antifungal activity of rhizome crude extracts on LPF were determined. The effect of inoculation of sterile seedlings by LPFs on the concentrations of rhizome phenolics was evaluated. The rates of growth inhibition amongst LPFs were determined. The LPFs had a strong negative effect on in sterile soil; microbiota in non-sterile soil eliminated such influence. There was an interactive inhibition among LPFs; the secondary metabolites also regulated their colonization in rhizomes. LPFs changed the accumulation of phenolics in . The results provide that colonization of LPFs in rhizomes was regulated by the colonizing microbiota of , the secondary metabolites in the rhizomes, and the mutual inhibition and competition between the different latent pathogens.