Fusarium and Alternaria fungi in grain of oats grown in the north-western Russia regarding cultivar specificity

Oat ( Avena sativa L.) is widely cultivated in a moist, cool climate and it is important crop particularly in Northern Europe. The most general usage of oat is for livestock feed. However, oat consumption as human food has recently increased, perhaps due to its reported health benefits. The abundance and species composition of the microbiota are the important factors in determining the quality of the grain. Fusarium fungi produce toxic metabolic products called mycotoxins. Mycotoxin contamination of food commodities can affect both human and animal health. Species of the genus Alternaria have rather less significance as the pathogens of cereals and sources of grain contamination. The aim of this study was to evaluate the natural infestation by Fusarium and Alternaria fungi of oat grain harvested in 2014 in the northwestern Russia. Asymptomatic seeds of 56 oat samples harvested in five provinces of the northwestern Russia (7 samples from Arkhangelsk and Pskov provinces, 20 samples from Vologda Province, 12 samples from Leningrad province and 10 samples from Novgorod Province) were assayed for the presence of filamentous fungi. Grain samples (except for a few unnamed) belonged to 14 varieties (Adamo, Argamak, Borets, Borrus, Krechet, Lev, LOS 3, Skakun, Scorpion, Teremok, Fukhs, Chernigovskiy, Chernigovskiy 83 and Yakov). Seeds were surface sterilized and placed on Petri dishes with Potato-dextrose agar (PDA). The resulting fungal colonies from each kernel were isolated and identified based on cultural and morphological features. Fungal contamination and the percentage of species belong to Fusarium or Alternaria fungi (%) were calculated in each sample. Mycological analysis revealed presence of different species of fungi belonging to the genera Alternaria, Aspergillus, Bipolaris, Cladosporium, Epicoccum, Fusarium, Penicillium, and others. The main representatives of mycobiota were Fusarium and Alternaria fungi. Infection of Fusarium fungi was detected in 88.9 % analyzed oat samples (average grain infestation in different regions ranged from 6.1 to 18.7 %, the maximum value was 64.0 %). Alternaria fungi were found in 91.0 % grain samples (average infestation ranged 1.5 to 48.0 %, the maximum value was 85.0 %). Among Fusarium fungi the F. poae, F. sporotrichioides and F. langsethiae which belong to trichothecene-producing species were detected with the highest frequency. A number of species, such as F. anguioides, F. avenaceum, F. graminearum, F. incarnatum, F. subglutinans, and F. tricinctum, were low-frequent. For the first time F. langsethiae was found on the territory of Arkhangelsk Province which is the most northern border of this fungus areal in Russia. The high positive correlation between portion of grains damaged by F. langsethiae and accumulation of T-2/HT-2 toxins was found. Fungi of Alternaria genus were mainly presented by toxin-producing species A. tenuissima and A. arborescens (66-86 % of the total number of Alternaria isolates). Cultivars Lev, Adamo, Yakov, Krechet were the most infected by Fusarium (an average infestation rate was more than 20 %). The significantly higher grain infection by Alternaria fungi was detected in cultivar Lev in comparison with another analyzed oat cultivars. The obtained data are in line with earlier reported results of toxicological analysis (A.A.Burkin et al., 2015) in which the presence of mycotoxins in the grain from all provinces of the northwestern Russia was revealed, particularly T-2/HT-2 toxins were found in 60.7 % of samples, deoxynivalenol was detected in 62.5 % and alternariol was presented in 29.0 % of the tested oat samples.