## 4 Discussion  
The purpose of this study was to identify filamentous fungi that inhabit American cranberry plants that grow in one of the largest commercial plantations in central Europe. The isolates tested were obtained from disinfested fragments of roots, leaves, and fruits of 1-, 2-, and 3-year-old plants that did not show visible disease symptoms. Identification was performed through a sequence analysis of the ITS region, which includes fragments ITS1 and ITS2 separated by the 5.88 gene and is located between the 188 rDNA and the 288 rDNA. This region is widely accepted as the universal primary DNA barcode marker [27]. If satisfactory identification was not achieved by analyzing the ITS region, one of the following secondary markers was used: DNA-directed RNA polymerase II subunit B (_RPB2_) or translation elongation factor 1 alpha (_TEF-1a_) [26]. According to [PERSON] et al. [28], approximately 20% of fungal DNA sequences deposited in public databases can be misidentified at the species level. Therefore, the search for reference strains that were most similar to tested isolates was restricted to data sets that contained type material described as holotypes, neotypes, lectotypes, or isotypes. The exceptions were _A. geophila_ and _P. sporulosa_ species, for which these types of nomenclature were not included in the NCBI database. The dominant group of the 141 isolates tested was soil-borne saprotrophs and endophytes. Thirty-five percent of them were included in the genera _Trichoderma_, _Paraphaesphaeria, Penicillium, and Aspergillus. Most Trichoderma isolates came from roots of 2- and 3-year-old plants. Their taxonomic positions were determined by analyzing the sequence of the _TEF-1\(\alpha\)_ gene and showed 95.25% to 98.06% identity with strains of T. _amoenum_ and _T. dorothopsis_. These species are exotic to central Europe and have been poorly described in the literature. The first strains of T. _dorothopsis_ were found in China, in soil from the Yangtze River basin, and in the rhizosphere of chili plants [29]. Meanwhile, T. _amoenum_ originated in the soil in Yunnan province [30]. The other species not yet recorded in Europe is T. _scalesiae_, which was found in tropical regions of the Galapagos Islands, the Philippines, and Indonesia [31; 32; 33]. The sequence of the ITS region of a fungus isolated from the root of the tested cranberry was 99.66% similar to that of this species. The remaining Trichoderma isolates showed the highest similarity to cosmopolitan species, such as T. _koningii_, T. _atrobrunneumum_, T. _insigne_, and T. _hamatum_. These fungi have been frequently isolated from soil, grass, sand, decaying plants and the rhizosphere [34; 35; 36; 37; 38; 39; 40; 41]. They are known for their antibiotic activity, secretion of cell-wall-degrading enzymes, and stimulation of plant growth. Among them, only strains of T. _hamatum_ have been reported on the leaves of American cranberry plants that grow in a botanical garden in Poland [15]. The common fungi in the tested plants were also members of the genus _Paraphaesphaeria_. The isolates obtained from roots of 1- and 2-year-old plants showed the greatest similarity to P. _sporulosa_. This species grouped strains from tissues of different plants, including _Festuca_ spp., _Fragaria_ sp., _Malus sytsteris_, _Pica abies_, _Triticum aestivum_, _Clematis_ sp., _Solanum tuberosum_, _Rosa cantina_, and _Opuntia_ spp. [42]. According to [PERSON] et al. [43], some of them showed antibiotic activity against _Salmonella enterica_. In fruit tissues, single isolates most similar to _S. aogashimaense_ were also found. This species has a broad host spectrum and can inhibit the growth of pathogens such as _Puccinia trticiua_, _P. Ivordei_, _P. coronata_, _Bipolaris sorokiniana_, _Alternaria alternata_, _Curvalaria trifolii_, _Blumeria gramitis_, and _Diplodia corticola_[44; 45; 46; 47].