Incidence and control of toxigenic fungi in stored cereals

Abstract

Monitoring of the incidence of toxigenic species and the detection of mycotoxins in stored cereals (maize, wheat and barley) are of a special importance for agriculture in Serbia. The essential reason for this is the fact that cereals, as species most susceptible to toxigenic fungi, are cultivated on over 60% of arable land, then the incidence of potentially toxigenic fungi and natural occurrence of certain mycotoxins has been registered each year, while epizooties of mycotoxicoses have been detected in some years. Under agroecological conditions of Serbia, F. graminearum and F. verticillioides are the most frequent species - the first, on grain of both, maize and small grains, and the later, more on maize, while the third species F. sporotrichioides, belonging to the most toxic species in the world, especially in maize, is scarce. Besides, other numerous, potentially toxigenic Fusarium species, including: F. subglutinans, F. proliferatum, F. oxysporum, F. tricinctum, F. poae, F. culmorum, etc. have been detected. A frequent and calamitous incidence of European corn borer (Ostrinia nubilalis) is one of many factors that favor the intensive development of potentially toxic fungal species, especially of F. verticillioides and F. subglutinans. Other toxigenic species of fungi, such as species of the genera Aspergillus and Penicillium, are less important than the Fusarium species. According to previous studies in Serbia, the occurrence of aflatoxin B1 and ochratoxin A (Aspergillus spp. and Penicillium spp) zearaleonones and trichothecenes type A (T-2 toxin and diacetoxyscirpenol) (Fusarium spp) in cereals and their products was determined in concentrations even higher than tolerance values obligatory by the running regulations for food and feed. There are little data or none on other types of mycotoxins. Possibilities of maize artificial drying in Serbia are limited, especially in the case of small producers, which make over 80% of all producers. Therefore, maize is mainly dried naturally and is stored in cribs, which provides a further development of potentially toxigenic species and more intensive biosynthesis of certain mycotoxins. Cereal growers are generally recommended to apply preventive measures in order to reduce the incidence of potentially toxigenic genotypes and their metabolites, as well as, to grow more resistant and early maturity genotypes, to apply optimum cropping practices, harvest at full maturity, separate ears with pathological changes and frequently perform control during winter and early spring. On the other hand, in the industrial animal growing, the use of preparations for adsorption of mycotoxins already synthesized in cereals such as Min-a-zel Plus, is recommended in the preventive concentrations of 0.2% or 0.4% in the case when higher concentrations of mycotoxins are detected in cereals or commercial mixed feed.

Sadržaj vlage, temperatura, stepen zaraze zrna pre skladištenja, prisustvo insekata, količina polomljenog zrna, prisustvo stranih materija, način sušenja i dužina čuvanja, glavni su činioci koji utiču da li će uskladištena žita (kukuruz, pšenica, ječam i ostale strnine) biti kontaminirana toksigenim gljivama i mikotoksinima. U nas su Fusarium vrste potencijalno najznačajnije toksigene vrste, a zatim vrste iz rodova Aspergillus i Penicillium. U žitima i njihovim prerađevinama utvrđena je prirodna pojava aflatoksina B1 i ohratoksina A (Aspergillus spp. i Penicillium spp) zearalenona i trihotecena tipa A (T-2 toksin i diacetoksiscirpenol) (Fusarium spp), čak i u većim koncentracijama nego što je to dozvoljeno prema našim važećim pravilnicima za ishranu ljudi i životinja. Proizvođačima žita, uglavnom, se preporučuju preventivne mere za redukciju pojave potencijalno toksigenih vrsta i njihovih sekundarnih metabolita, kako u poljskim uslovima, tako i tokom čuvanja.