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Fusarium equiseti (Corda) Saccardo is a soil saprophyte and a weak pathogen, associated with several diseases of fruit and other crops in subtropical and tropical areas, but also in countries with temperate climate. A wide range of secondary metabolites has been identified among natural F. equiseti populations, with zearalenone (ZEA), fusarochromanone and fusarenon-X being the most common. In present study, the genetic diversity of strains from two populations (from Italy and Poland) was evaluated by analysing the translation elongation factor 1? (tef-1?) sequences, two polyketide synthases from the ZEA biosynthetic pathway (PKS13 and PKS4) and the TRI5 gene from the trichothecene biosynthetic pathway. ZEA was produced in rice cultures by 20 of the 27 tested isolates in concentrations ranging from 1.34 ng/g to 34,000 ng/g). The ability to produce enniatins and trichothecenes was evaluated in all strains by identifying esyn1, TRI13 and TRI4 genes. The presence of PKS4 and PKS13 genes was confirmed by polymerase chain reaction (PCR) in only some ZEA-producing isolates. Similarly, the TRI5 gene was found in 14 of the 27 isolates tested. This is likely to have been caused by the divergence of those genes between F. equiseti and F. graminearum (the latter species was used for the primers design) and can be exploited in phylogenetic studies. The analysis of the mycotoxin biosynthetic gene sequences can be used to differentiate the studied genotypes even more precisely than the analysis of the non-coding regions (like tef-1alpha).
Ochratoxin A (OA), zearalenone (ZON), moniliformin (MON) as well as trichotecenes and fumonisines (FUM) are naturally occurring contaminants of cereals and animal feed. They pose a health risk not only to humans but also to livestock and, as a consequence, may cause economical losses either due to unfavorable effects on domestic animals themselves or to an increased potential for health effects in human beings consuming mycotoxin-contaminated edible animal products. At present, large-scale studies are carried out in EU countries to determine a safe, admissible concentration of these toxins in cereals and their processed products. The aim of this review is to collect and summarize information concerning the properties, occurrence and toxicity of these mycotoxins.
The aim of the present study was to examine the abilities of twenty-four isolates belonging to ten different Trichoderma species (i.e., Trichoderma atroviride, Trichoderma citrinoviride, Trichoderma cremeum, Trichoderma hamatum, Trichoderma harzianum, Trichoderma koningiopsis, Trichoderma longibrachiatum, Trichoderma longipile, Trichoderma viride and Trichoderma viridescens) to inhibit the mycelial growth and mycotoxin production by five Fusarium strains (i.e., Fusarium avenaceum, Fusarium cerealis, Fusarium culmorum, Fusarium graminearum and Fusarium temperatum). Dual-culture bioassay on potato dextrose agar (PDA) medium clearly documented that all of the Trichoderma strains used in the study were capable of influencing the mycelial growth of at least four of all five Fusarium species on the fourth day after co-inoculation, when there was the first apparent physical contact between antagonist and pathogen. The qualitative evaluation of the interaction between the colonies after 14 days of co-culturing on PDA medium showed that ten Trichoderma strains completely overgrew and sporulated on the colony at least one of the tested Fusarium species. Whereas, the microscopic assay provided evidence that only T. atroviride AN240 and T. viride AN255 formed dense coils around the hyphae of the pathogen from where penetration took place. Of all screened Trichoderma strains, T. atroviride AN240 was also found to be the most efficient (69–100% toxin reduction) suppressors of mycotoxins (deoxynivalenol, 3-acetyl-deoxynivalenol, 15-acetyl-deoxynivalenol, nivalenol, zearalenone, beauvericin, moniliformin) production by all five Fusarium species on solid substrates. This research suggests that T. atroviride AN240 can be a promising candidate for the biological control of toxigenic Fusarium species.
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