Mycology and Phytopathology

The study of fungal and prokaryotic communities in the unique ecosystems of the Arctic seas is very important for understanding global biogeochemical cycles and developing approaches to bioremediation of these ecosystems. Using high-throughput sequencing of the variable regions ITS1/ITS2 (in the fungal genome) and V3–V4 of the 16S rRNA gene (in the bacterial genome), the species composition and taxonomic structure of fungal and heterotrophic bacterial communities in the surface bottom sediments of the Kara Sea from depths of 16 to 417 m were studied. The fungal biome was dominated by operational taxonomic units (OTUs) of the Ascomycota (more than 50% of ITS reads in each of the 12 samples), followed by the Basidiomycota division (10–20%). This mark for Сhytridiomycota did not exceed 2% of ITS reads. No significant differences in the mycobiome structure of the Kara Sea bottom sediments were found depending on the sampling depth. OTUs of the Sordariomycetes and Eurotiomycetes (Aspergillaceae) prevailed. Basidiomycetes are represented mainly by yeast organisms of the Filobasidiaceae, Malasseziaceae, Sporidiobolaceae, and Tremellaceae. According to fluorescence microscopy, the total number of fungal propagules was in the range of 207–546 thousand spores and mycelial fragments per 1 g of bottom sediment, and their minimum values were recorded at greater depths. All the studied stations were found to contain numerous aerobic heterotrophic bacteria belonging to various families, orders, and classes of the phyla Pseudomonadota, Actinomycetota, Bacteroidota, Verrucomicrobiota, Gemmatimonadota, Myxococcota, and Acidobacteriota. An interesting fact is the discovery of nucleotide sequences characteristic of strict anaerobes in these upper oxidized bottom sediments of the Kara Sea: sulfate-reducing bacteria from the phylum Thermodesulfobacteriota and chemoheterotrophic bacteria from the Anaerolineae (phylum Chloroflexota). The data obtained significantly expand our knowledge of the diversity of fungi and bacteria, key heterotrophic organisms – destructors of organic matter in the bottom sediments of the Arctic seas.

Using renewable resources to create polymeric materials is one of the ways to achieve sustainable development goals. The currently used hydrocarbon-based plastics decompose over a long time, accumulating and causing environmental pollution. One way to solve the problem of plastic waste is to develop polymers based on plant materials. Mycopolymers are completely biodegradable polymers consisting of lingo-cellulose particles. Mycelia of xylotrophic basidiomycetes are the binding component. The resulting material can be used as insulation, packaging, or in the manufacture of interior items and furniture. The following xylotrophic agaricomycetes were studied in the work, Pleurotus eryngii, P. ostreatus, Trametes hirsuta, T. versicolor, T. pubescens, T. ochracea, Phellinus igniarius, Fomitopsis pinicola, F. betulina, Ganoderma lucidum, G. applanatum, Fomes fomentarius and two types of substrates based on wood waste Populus tremula and Betula pendula. The most durable mycopolymers were obtained on the basis of Ganoderma applanatum and F. fomentarius.

Phoma-like fungi is an extensive, non-taxonomic group of anamorphic ascomycetes, currently incorporating all micromycetes that were previously consumed as species of the genus Phoma. Didymellaceae is one of the largest families in the Pleosporales with a unique and underestimated biodiversity, encompassing main genera of Phoma-like fungi, namely Ascochyta, Didymella, Stagonosporopsis, etc. Several Convolvulaceae wild plants are widespread and one of the most harmful weeds, successful in many types of climates, are an exceptional source of biodiversity of Didymellaceae fungi. Phytosanitary examination of industrial fields, natural and ruderal areas has been carried out by authors from 1990 to the present. Leaves of Convolvulaceae plants (Calystegia inflata, Calystegia sepium, Calystegia sp., Convolvulus arvensis, Ipomoea purpurea) with symptoms of fungal etiology, namely leaf spots were collected in in different locations in Russia and neighboring countries (Kazakhstan, Kyrgyzstan). As a result of monitoring, a rich collection of fungal Phoma-like strains (at least 200) has been created and maintained. The aim of this study was to identify 28 Didymellaceae spp. strains isolated from Convolvulaceae plants according to the consolidated species concept (CSC) by their phylogenetic, micromorphological, and cultural features. Multilocus phylogenetic analysis inferred from nucleotide sequences of the internal transcribed spacer (ITS) and large subunit (28S) of ribosomal DNA, partial DNA-directed RNA polymerase II subunit (rpb2), and β-tubulin (tub2) genes revealed well-supported monophyletic clades corresponding to 18 Didymellaceae species. Among them: Ascochyta erotica, Didymella americana, D. bellidis, D. glomerata, D. macrostoma, D. pomorum, D. pseudomacrophylla, D. segeticola, D. sinensis, D. tanaceti, Epicoccum convolvulicola, E. pseudoplurivorum, Nothophoma brennandiae, N. gossypiicola, Phomatodes nebulosa, Stagonosporopsis caricae, S. heliopsidis, and S. inoxydabilis. Plants of the Convolvulaceae family were recorded as substrates for all identified fungal species for the first time. Seven species were revealed in Russia for the first time D. bellidis, D. segeticola, D. sinensis. D. tanaceti, Nothophoma brennandiae, Phomatodes nebulosa, and Stagonosporopsis caricae. Stagonosporopsis heliopsidis for the first time was found in the Kazakhstan. Additionally to detailed phylogenetic data, the manuscript is accompained with a detailed description of the cultural and micromorphological features of all species.

Tomato (Solanum lycopersicum) is one of the most widely cultivated vegetable crops in Russia. Fungi of the genus Fusarium are among the most significant tomato pathogens, causing wilt and fruit rot. This study investigated the species composition and pathogenicity of Fusarium strains isolated from tomato plants across different regions of Russia using molecular methods. Tomato tissues samples exhibiting fungal disease symptoms were collected during the growing season from commercial open-field farms in the Moscow, Astrakhan, and Saratov regions, as well as the Krasnodar Territory. A total of 25 Fusarium strains were isolated: 19 strains were isolated from fruits, two from leaves, one from the stem and 3 from roots. DNA analysis of tef1α and β-tubulin regions identified nine species within three species complexes: the Fusarium incarnatum-equiseti complex (F. citri, F. clavum, F. compactum, F. luffae), the Fusarium fujikuroi complex (F. annulatum, F. proliferatum), and the Fusarium oxysporum complex (F. curvatum, F. fabacearum, F. nirenbergiae). F. curvatum was isolated from the roots of a plant with wilt symptoms, while F. fabacearum was recovered from the roots of asymptomatic plants and from fruits. F. luffae was isolated from the stem of the plant with wilt symptoms and from diseased fruit. F. clavum strains were isolated from leaves with dark necrotic spots and from fruits. Strains of F. citri, F. clavum, F. compactum, F. annulatum, F. proliferatum, and F. nirenbergiae were isolated from fruits with fungal disease symptoms. All analyzed strains successfully infected tomato fruits and potato tubers in a spore suspension injection test. The most aggressive species were F. compactum and F. nirenbergiae, with F. compactum capable of infecting healthy fruits with intact skin. Strains of F. clavum also infected healthy tomato fruits, but the infection developed more slowly than with F. compactum. This study is the first to demonstrate the pathogenicity of F. compactum, F. annulatum, F. fabacearum, and F. nirenbergiae in tomatoes. These findings expand current knowledge on the diversity of Fusarium species associated with diseased tomato tissues.