Sixty six genotypes belong to wild and cultivated Avena species from the VIR collection were evaluated for infection of grain by Fusarium fungi and mycotoxins in accumulation. Among genotypes 13.6, 28.8, and 57.6% were diploid, tetraploid, and hexaploid oats, respectively. The aim of this study was to recognize the interrelationship between the wild species of the genus Avena not subjected to formal breeding programs, and Fusarium fungi, which have been reported as predominant seed borne pathogens. The real-time PCR was used to simultaneously detect and quantify fungi in grain of Avena genotypes. Mycotoxin analysis was performed by ELISA. The average amount of Fusarium DNA and deoxynivalenol (DON) in groups of the tetraploid oats were higher than they were found in the groups of di- and hexaploid species. It was determining the strong correlation between the presence of Tri-Fusarium DNA and DON content (p < 0,01). The low amounts of DON in the grain were detected in seven hexaploid genotypes (A. byzantina, A. sterilis, A. sativa, and A. fatua) and one diploid A. wiestii. The connection of morphological characters (weight of 1000 grains, husk hardness, trichomes profusion and plant height) of Avena species and the indicators of Fusarium infection were analyzed. Only biomass of Fusarium has demonstrated significant connection with weight of 1000 grains. Significant correlation between the hardness of husk and the amounts of Fusarium DNA (p < 0,01) was detected. For Fusarium the strong protective effect of the husk from the penetration of pathogens into grain was evident.