A specific variety of microscopic fungi of the sort Fusarium of the grades zoned for Siberia and se-lection lines of wheat and barley were investigated. It was established that the contamination of grain of separate grades significantly varied: the level of general contamination of microscopic mushrooms made 20-51 %, the contamination of average sample fungi of the sort Fusarium varied within 4-23 % on wheat and 20-26 % - on barley. The max-imum infection was found in all studied varieties of barley and wheat varieties Chaghytai (25 %), Yunata (22 %), OmGAU (21 %) and Heracles (22 %); minimum contamination was noted in fuzarium infection in the grades Vetluzhanka, Omsk-32 (on 3.5 %), and also the selection K1629 and K174-1 lines - 3 and 4.5 % respectively. The complex of fungi of the sort Fusarium on grain of wheat includ-ed 11 types; on barley - 8 types. The type of F.sporotrichioides which share was from 20 to 67 % of total quantity of fuzarium fungi was dominating. It is also necessary to consider the types of F.avenaceum, F.culmorum, F.oxysporum, F.sambucinum and F.semitectum as potentially leading to the development of fusariosis owing to their high occurrence on grain of separate grades. The increase in specific variety was characteristic for grades with general high contamination with micromycetes and fusariosis. The reduction of bio-diversity to 3-4 species leads to dangerous in-crease of toxicogenic species F.sporotrichioides (up to 67 %) and increases the danger of accumu-lation of mycotoxins in grain. The pool of Fusarium fungi in the rhizosphere of wheat was stable during vegetative period; the maximum number was noted at the time of mass emergence of shoots and at the end of vegetation which was connected with emer-gence and the maximum accumulation of nutrients in a root zone. Qualitative composition was repre-sented by six types; the dominant position in all variants had the type of F.sporotrichioides (36- 45 %.)