Relevance. Currently, the relevance of studying to identify the ability of many micromycetes to synthesize phytotoxic substances that reduce seed germination and lead to huge losses in the yield of strategic agricultural crops is increasing. To solve the problem, the development of new methodological approaches is required, which is significant for immunologists and phytopathologists.The purpose of this work is to determine the phytotoxic activity of micromycete strains from the genera Fusarium, Alternaria, Bipolaris, parasitizing on all agricultural crops cultivated in Russia.Materials and methods. The strains, the methods of their cultivation, the bioassay method were used, and the statistical processing of the results obtained was carried out. A modification of some methodological approaches for assessing the phytotoxicity of micromycetes has been carried out. The selection of representative concentrations of culture fluid filtrates (FCF) of strains for phytotoxicity evaluation was carried out.Results. A correlation was established for all variants of the experiment between two independent parameters: the development parameters of wheat seedlings and the concentration of cultural liquid filtrates. New results have been obtained on the study of the phytotoxic activity of 70 strains of hemibiotrophic micromycetes and the optimal concentrations of fungal FAs for classifying fungal strains into toxicity groups have been established. The most variable toxicity values were found when using a 40% solution of FCL. It was shown that, under these conditions, fungal strains can be divided according to the degree of toxicity into significantly different groups. This circumstance is an important reason for including strains of micromycetes with certain toxicity properties in the State Collection of Phytopathogenic Microorganisms. Fungal strains are necessary and appropriate for use in breeding to create resistant and tolerant varieties to phytopathogens from the genera Fusarium, Alternaria, Bipolaris.Conclusion. New methodological approaches have confirmed that the most variable toxicity values were found with the use of FCF in a ratio of 2:3. This concentration of FCF strains are divided into 4 groups with characteristic differences in the degree of toxicity, which is an important reason for including such strains of micromycetes in the State Collection of Phytopathogenic Microorganisms and will be further used in breeding to create resistant and tolerant varieties of agricultural crops.

Relevance. Under conditions of prolonged storage of fungi on a nutrient agar medium, their pathogenic properties are gradually lost. Preservation of collection material with unchanged pathogenic properties is necessary for correct research, including the development of biological protection methods, monitoring of pathogen development dynamics, assessment of their virulence and aggressiveness, choice of selection material.Materials and Methods. The ability to the resumption of full-fledged species characteristics on the culture nutrient agar medium after long-term storage of the biomaterial in the form of a lyophilizate under conditions of low positive +4°C and ultra-low temperatures of -80°C of Alternaria alternata (Fr.) Keissl., Bipolaris sorokiniana Shoemaker and Fusarium solani (Mart.) Sacc. strains stored in the State Collection of Phytopathogenic Microorganisms of the All-Russian Research Institute of Phytopathology (ARRIP) was studied. The viability of fungi was judged by their ability to form spore-forming colonies on a nutrient medium, pathogenicity and phytotoxicity by the reaction of test culture seedlings to the effects of spore suspensions and culture fluid filtrates.Results. Long-term storage of Alternaria alternata, Bipolaris sorokiniana and Fusarium solani strains in a freeze-dried state, both at low and ultra-low temperatures, did not adversely affect their viability. On the 14th day of culture on a nutrient medium, fungal strains formed sporulating colonies comparable to the control variants. Comparison of pathogenicity signs in fungal strains before the experiment and after storage did not reveal significant differences between the variants. When studying the effect of the culture liquid filtrates of fungal strains on the development of the test culture, a differentiating effect of the storage regime at +4oC was established, while under ultra-low temperatures the results in the variants practically did not differ.Conclusion. The results of the study were showed that the lyophilization of biomaterial,including imperfect species of fungi for long-term storage at low positive and ultra-low temperatures is relevant and in demand in many scientific and industrial institutions.

Relevance. Common buckwheat is one of the most important cereal and melliferous crops being in demand both in Russia and overseas. Despite the fact that buckwheat has lower sus- ceptibility to infectious diseases in comparisons with other grain and cereal crops, research on its pathogens is a topical issue considering a high disease rate for this crop in Primorsky krai. Materials and methods. The study on pathogenic composition was conducted in selective crop rotations of FSBSI “FSC of Agricultural Biotechnology of the Far East named after A.K. Chaiki” at the territory of Ussuriysky district in Primorsky krai. Indeterminate (Izumrud, Pri 7, Bashkirskaya krasnostebel’naya) and determinate (Dikul) buckwheat varieties were used for the study. Fungi were isolated from rhizoplane using water washing technique, from soil and rhizosphere via the dilution method, from leaves and root systems by accumulation in a moist chamber with subsequent transfer of culture onto selective medium. Fungal isolates were cul- tivated on toxigenic medium (Myro) to determine their phytotoxicity. Phytopathogenic activity of living cultures was evaluated on potato sucrose agar according to the modified method of Chelkowski and Manka . All experiments were conducted in accordance with established methods.Results. Culture filtrates of F. avenaceum and F. graminearum isolates, obtained from different anatomical parts of common buckwheat, were characterized by low toxicity, and culture filtrates of F. oxysporum isolate were highly toxic. Phytotoxicity of pathogens manifested itself not only in decrease in laboratory germination ability of buckwheat seeds, but also in inhibition of buckwheat sprout development. It proved that metabolites exerted a prolonged effect on sensitive plants. F.avenaceum, F. oxysporum and F. graminearum have pronounced phy- topathogenic and aggressive properties in relation to buckwheat and test-plants in the laboratory conditions. The sum total of their studied phytotoxic properties is convincing enough to consider them potentially hazardous to buckwheat for wilt disease development.