A fungus was isolated from diseased roots of Cucumis sativus grown in greenhouses. The morphological and cultural characteristics of the isolate allowed it to be classified as Plectosphaerella melonis. BLASTn analysis revealed 99% homology of the ITS sequence from the isolate with 14 Acremonium cucurbitacearum and P. melonis isolates, allowing attribution of the isolate to P. melonis (syn. A. cucurbitacearum). Koch’s hypothesis requirements were fulfilled for the isolate. Symptoms on host roots developed after 14 d of growing cucumber plants on infested soil. Plants of the cucumber variety Nizhynskyi 12 were very susceptible at the two leaf growth stage (2 weeks after sowing). Above-ground disease symptoms were absent after 14 d, even with severely diseased roots. This is the first report of P. melonis on C. sativus in Ukraine.

In the last ten years, many countries around the world recorded a new disease of the Cucurbitaceae, the agent of which was P. melonis. The ability of P. melonis 502 to form intracellular mycelium in the epidermal and parenchymal tissues of roots was shown. Leading tissues (xylem and phloem) did not colonize, which indicates the impossibility of plant vessel clogging and shows the fungus’s biochemical effects on plants, which causes the process of pathogenesis. P. melonis 502 is able to develop in a wide range of pH values, while the pH-optimum is 8.5. P. melonis 502 is able to adjust the pH of the medium to the optimal value—8.5. We also showed that cellulase enzyme synthesis depends on pH. We studied the exo-, endo- and β-glucasidase activity of P. melonis 502 and found that the highest activity of cellulase enzymes was on a medium whose pH was 8.5. In the process, the total cellulolytic activity was 0.326 U mL−1, exoglucanase activity—0.539 U mL−1, endoglucanase activity—0.950 U mL−1 and β-glucosidase activity—0.795 U mL−1.

Objective. Screening of microorganisms — antagonists of the phytopathogenic fungus Acremonium cucurbitacearum. Methods. The antagonistic activity of microorganisms was investigated by the method of mixed (counter) cultures on wort agar. The appearance and type of relationships were registered using Simonian and Mamikonian modified scale. The primary screening of A. cucurbitacearum 502 antagonists was performed by the delayed antagonism method. Morphological and cultural characteristics of Triсhoderma sp. 017 were studied on wort agar. The fungus was grown for 10 days. Results. Almost all of the microorganisms under study were found to exhibit antagonistic properties against A. cucurbitacearum 502. In particular, among bacteria, Bacillus sp. 23 exhibited the highest antifungal activity and inhibited the growth of the pathogen even after 25 days of their compatible cultivation. Screening for micromycetes of the genera Trichoderma and Chaetomium showed that all the tested strains showed antagonistic activity to A. cucurbitacearum 502 to one extent or another. Following contact of Chaetomium fungi — C. globosum 377 and C. cochliodes 3250 with A. cucurbitacearum 502, they delayed growth of the latter, showing superparasitism at Day 25 and 15, respectively. Among the fungi of the genus Triсhoderma, strain Triсhoderma sp. 017 was characterized by the fastest growth and at Day 5 of cultivation showed superparasitism, arresting the growth of A. cucurbitacearum 502 and completely invading the colony of pathogen. Colonies of the fungus Trichoderma sp. 017 on wort agar show rapid growth, forming a white mycelium film and a dark green conidial zone. The optimum pH is 5.0. The mycelium consists of colourless, smooth, strongly branched hyphae, 2.5‒6.0 μm in diameter. Conidiophores are very branched in compact or loose pads, with a main axis, 3.5‒4.0 µm thick. Sterigmata form rings with 2‒3 sterigmata varying in size, 6.25‒15.0 × 2.5‒3.0 μm. Conidia are spherical 2.0‒3.0 × 3.5‒5.0 μm. Conclusion. Therefore, in order to protect plants from acremoniasis caused by the phytopathogen A. cucurbitacearum, we suggest the strain Triсhoderma sp. 017, which is characterized by the most rapid growth and active superparasitism. According to morphological and cultural characteristics, the fungus is classified as T. viride 017.

Goal. To investigate the antagonistic activity of a new strain of Trichoderma viride F-100076and its effect on the formation of micromycetes populations in the root zone of corn plants underfield conditions. Methods. The antagonistic activity of T. viride F-100076 was studied by the method of mixed (counter) cultures on wort agar using phytopathogenic fungi, which were isolated andidentified in the Laboratory of Plant-Microbial Interactions. The appearance and type of relationship were registered using a scale modified by Symonian and Mamikonian. The number of micromycetes was determined by the method of soil dilutions. Isolation, accounting and cultivation of fungiwas carried out according to conventional methods. Micromycetes were identified according to thedeterminants appropriate for a specific systematic group of micromycetes. Results. It was foundthat T. viride IMB F-100076 is characterized by high antagonistic activity against a wide range ofphytopathogenic fungi, showing hyperparasitism as early as on the eighth day. The highest antagonistic activity of the strain was found against: Alternaria radicina, Acremonium strictum, Acremonium сucurbitacearum, Fusarium oxysporum var. orthoceras, Fusarium moniliforme var. lactis, Torula expansa (5 points on the corresponding Symonian and Mamikonian scale). Data from the mycological analysis of the sod-podzolic soil of the corn rhizosphere showed that the mycocenosis ofthe sod-podzolic soil of the corn rhizosphere was formed by micromycetes belonging to the generaAcremonium Link, Cladosporium Corda, Fusarium Link:Fr, Gliocladium Corda, Mucor Mich, Penicillium Link:Fr, Rhizopus Ehrenb, Trichoderma Hers, among which the most represented were micromycetes of the genus Penicillium (59 %). The total number of fungi in the control variant was291.00 ± 79.67 thousand CFU/g of soil. The introduction of straw affected both the total number ofmicromycetes and the genus composition of fungi. The total number of fungi in the variant withstraw increased 2.6 times and amounted to 744.00 ± 114.67 thousand CFU/g of soil. The number ofrepresentatives of all studied genera of micromycetes also increased. In addition, the introductionof straw provoked the development of fungi of Bipolaris and Fusarium genera, which can be considered a negative outcome since representatives of these species are commonly recognised as pathogens of root diseases. Application of the fungus antagonist T. viride IMB F-100076 to the soilalong with straw did not significantly affect the total number of micromycetes. At the same time, a displacement of fungi of the genus Bipolaris and Fusarium from the rhizosphere of corn was registered.The number of fusaria decreased from 96.00 ± 5.44 to 23.00 ± 2.32 thousand CFU/g of soil or almost4 times and reached the level of the control variant. Fungi of the genus Bipolaris in the variant withthe introduction of trichoderma were not detected. Conclusion. The antagonist fungus T. virideF-100076, introduced into the soil along with straw, strikes root in the soil and exhibits antagonisticactivity against micromycetes of the genera Bipolaris and Fusarium, which are commonly represented by root rot pathogens of many crops. Thus, the new strain T. viride F-100076 allows increasing theantagonistic potential of the rhizosphere soil of corn and protecting plants from pathogens.

Aim. A review of the literature to establish the mechanisms of the main mutualistic interactions that are important for the potential application of symbiotic fungi as biofertilizers, bioprotectors and bioregulators for more sustainable and so-called greening agriculture, soil restoration and understanding the role of microsymbionts in natural ecosystems. Methods. Comparative analysis of scientific literature. Results. Root mycorrhization is a potent factor of plant growth intensification, metabolic processes activation and macro-organism development improvement. Mycorrhiza formation is notable for angiosperms and gymnosperms, yet many representatives of bryophytes, ferns, and mosses also reveal (other) close symbiotic relations with fungi. Mycorrhizal fungi account for about 10 % of identified fungal species, including essentially all of the Glomeromycota and substantial fractions of the Ascomycota and Basidiomycota. De- pending on the fungal structures and microsymbiont position in tissues or cells of the macrosymbiont, arbuscular, ericoid, arbutoid, monotropoid, orchid mycorrhiza and so-called ectendomycorrhiza, and ectomycorrhiza are distinguished. This review gives an overview of the signalling interaction between partners and the bidirectional mechanism of nutrient exchange or other mutual benefits. Conclusions. Microscopic saprophytic fungi, capable of penetrating plant roots and playing a critical role in plant adaptation to abiotic and biotic stressors, are of special interest in mutualistic symbioses. In addition, while forming mutualistic symbioses with plants, the saprophytic fungi promote bio- mass increase and enhance the food traits of plants. The type of interaction depends on both micro- and macrosymbiot; it may in some cases and for some organisms fluctuate from mutualistic, commensalistic to antagonistic, even parasitic interactions, demonstrating different stages of mutualism evolution and co-habitation and/or evolution of plants and fungi. A better understanding of the diverse roles of symbiotic microorganisms in ecosystems will improve the ways of their application in agriculture.