Advances in mycotoxicological research of forage grain crops

Recently, production of forage from the vegetative mass of grain crops has been steadily growing in Russia (Z.L. Fedorova, L.V. Romanenko, 2016; V.V. Popov, 2017; E.A. Volkova et al., 2018). For the successful and safe use of these products, it is extremely important not only to strictly observe the recommended terms, mowing height, drying conditions and technology of silaging grain-stem mass, but also to have the most complete information about the sanitary quality of raw materials. The study of the peculiarities of contamination by toxigenic microscopic fungi and mycotoxins of wild and cultivated cereals has already begun (G.Yu. Laptev et al., 2014; A.A. Burkin, G.P. Kononenko, 2015; G.P. Kononenko et al., 2015; E.A. Yildirim et al., 2019). However, this aspect has not been studied with a focus on forage crops. This work, for the first time, presents data on contamination of vegetative grain crops with toxic metabolites of microscopic fungi and on changes in the content of mycotoxins over phases of plant development and in ears at the beginning of grain maturation. The aim of this work was a mycotoxicological study of common barley ( Hordeum vulgare L.), soft wheat ( Triticum aestivum L.), and oats ( Avena sativa L.) during in the periods optimal for hay harvesting and in unripe ears of wheat and barley. The samples (spring barley H. vulgare cv. Vladimir, spring soft wheat T. aestivum cv. Ivolga, and oats A. sativa cv. Skakun) were collected from April 24 to August 11, 2019 (the fields of the Russian State Agrarian University - Moscow Timiryazev Agricultural Academy and the Williams Federal Scientific Center for Feed Production and Agroecology, Moscow Province). Beginning of tillering-ligule formation was noted as period 1, opening of the flag leaf envelope and appearance of the awns above the ligule-early milk ripeness - as period 2. At the stage of grain maturation, from the aboveground parts cut 3-5 cm from the soil surface the ears were separated. The concentrations of T-2 toxin (T-2), deoxynivalenol (DON), zearalenone (ZEN), fumonisins (FUM), alternariol (AOL), roridin A (ROA), aflatoxin B1 (AB1), sterigmatocystin (STE), cyclopiazonic acid (CPA), emodin (EMO), ochratoxin A (OA), citrinin (CIT), mycophenolic acid (MPA), PR toxin (PR), and ergot alkaloids (EA) were measured by indirect competitive enzyme immunoassay (ELISA) test. The detected load of mycotoxins was generally low. AOL, EMO were present in small and comparable amounts of 15-32 μg/kg and 14-29 μg/kg, as well as CPA and EA with wider ranges of variation, from 34 to 180 μg/kg and from 2 to 115 μg/kg. Fusariotoxins T-2, DON, and ZEN appeared in single samples, and FUM was not detected. ROA was also absent, and PR was extremely rare and detected only in one sample of wheat. In all crops, tens of μg/kg MPA and STE were found, and AB1 amounted to 1-3 μg/kg. Combined contamination of OA and CIT occurred only in barley (more often at tillering and ligule formation), while OA contamination occurred, though rare, in wheat and oats at the levels close to the detection limit. Lower contamination by mycotoxins was characteristic of vegetative oat plants compared to barley and wheat, which is practically important since fodder oat is popular as a green fodder for preservation, both separately and in crop mixtures. Wheat and barley ears at the beginning of grain maturation were noticeably different from the aboveground parts of the plants and showed a uniform tendency to reduce the frequency of mycotoxin detection to single cases or complete absence while maintaining the occurrence of EMO.