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Mycotoxins are a significant food safety concern. Aflatoxins, trichothecenes, fumonisins, and ochratoxin A are considered the most important mycotoxins due to their frequent occurrence in food products and their well-known toxicity. The regulation of mycotoxin biosynthesis occurs mainly at transcriptional level, and specific regulators have been described in every biosynthetic cluster. Secondary metabolite production, including mycotoxin synthesis, is also regulated by general regulator pathways affected by light, osmotic stress and oxidative stress, among others. This review is focused on this genetic regulation of mycotoxin biosynthesis by specific genes and global regulators.

Fusarium verticillioides is considered to be the main source of fumonisins, a group of toxins that contaminate commodities and result in chronic and acute diseases affecting humans and animals. The detection and control of this species is crucial to prevent fumonisins from entering the food chain. The objective of the present research was to develop a specific, sensitive, and robust PCR assay to detect F. verticillioides strains using two pairs of specific primers for F. verticillioides, which have been designed on the basis of the intergenic spacer region of the rDNA units. The first pair of primers was F. verticillioides species specific, whereas the second pair of primers detected fumonisin-producing F. verticillioides strains. This second pair of primers allowed for the discrimination between the major group of F. verticillioides strains, fumonisin-producing strains that are mainly associated with crops, and a minor group of strains, non-fumonisin-producing strains that are associated with bananas. Fifty-four strains of F. verticillioides from different geographical regions and hosts were tested using both sets of primers. Sixteen additional Fusarium species were examined. The specificity of the primer sequences provides the basis for a simple, rapid, accurate, and sensitive detection and identification method of this fungal species that represents a risk for human and animal health.

Summary: In the present report, a total of thirty-one isolates of Gibberella fujikuroi (Sawada) Wollenw. species complex of Fusarium (section Liseola) morphologically classified as F. moniliforme according to the taxonomy of Nelson, Toussoun and Marasas (1983) were analyzed for their ability to produce fumonisin B1 and fumonisin B2 by an optimized liquid chromatographic method. They were isolated from three hosts (Zea mays, Musa sapientum and Pinus pinea). The results indicate that M. sapientum is a preferential host for G. fujikuroi isolates with low or null capacity for producing fumonisins, while isolates from Z. mays and P. pinea are generally high fumonisin producers. The molecular characterization of isolates was carried out in parallel using an optimized, simple and low-cost method for isolating DNA from filamentous fungi and polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) of the rDNA intergenic spacer (IGS) region. The haplotypes obtained with Hha I enzyme and combinations of Hha I, EcoR I, Alu I, Pst I and Xho I enzymes provided very characteristic groupings of G. fujikuroi isolates as a function of host type and fumonisin B1 and B2 producing capacity. IGS region restriction patterns showed no relationship to isolate geographical origin. This is the first report on this method''s capacity to detect polymorphism permitting discrimination between G. fujikuroi isolates from different hosts and with different toxigenic profiles. [Copyright &y& Elsevier]

Maize expressing Cry1Ab insecticidal toxin (Bt maize) is an effective method to control Sesamia nonagrioides and Ostrinia nubilalis, the most damaging corn borers of southern Europe. In this area, maize is prone to Fusarium infections, which can produce mycotoxins that pose a serious risk to human and animal health, causing significant economic losses in the agrifood industry. To investigate the influence of corn borer damage on the presence of Fusarium species and their mycotoxins, Bt maize ears and insect-damaged ears of non-Bt maize were collected from commercial fields in three Bt maize growing areas in Spain, and differences in contamination were assessed. Additionally, larvae of both borer species were collected to evaluate their role as vectors of these molds. Non-Bt maize ears showed significantly higher presence of F. verticillioides, F. proliferatum, and F. subglutinans than Bt maize ears. For the first time, Fusarium species have been isolated from larvae of the two species. The most frequently found mycotoxins in ears were fumonisins, with non-Bt ears being significantly more contaminated than those of Bt maize. High levels of fumonisins were shown to correlate with the occurrence of corn borers in the ear and the presence of F. verticillioides and F. proliferatum. [ABSTRACT FROM AUTHOR]

Mycotoxin contamination is one of the main problems affecting corn production, due to its significant risk to human and animal health. The Fusarium and Aspergillus species are the main producers of mycotoxins in maize, infecting both pre-harvest and during storage. In this work, we evaluated the presence of mycotoxins and their producing species along maize production cycles in three different stages (anthesis, harvest, and storage) during three consecutive seasons (2016–2018). Fungal occurrences were studied using species-specific PCR protocols, whereas mycotoxin levels were determined by LC-MS/MS. Fumonisin-producing Fusarium species (F. verticillioides and F. proliferatum), as well as the aflatoxin producer Aspergillus flavus, were the most predominant species at all stages; although, during some seasons, the presence of F. graminearum and A. niger aggregate species were also identified. Contrastingly, fumonisins were the only mycotoxins detected and levels were always under legal regulations. The results presented here demonstrate that even when fungal contamination occurs at the early stages of the maize production cycle, the application of good agricultural and storage practices might be crucial to ensure mycotoxin-free grains. [ABSTRACT FROM AUTHOR]

The Aspergillus niger aggregate contains 15 morphologically indistinguishable species which presence is related to ochratoxin A (OTA) and fumonisin B 2 (FB 2) contamination of foodstuffs. The taxonomy of this group was recently reevaluated and there is a need of new studies regarding the risk that these species might pose to food security. 258 isolates of A. niger aggregate obtained from a variety of products from Spain were classified by molecular methods being A. tubingensis the most frequently occurring (67.5%) followed by A. welwitschiae (19.4%) and A. niger (11.7%). Their potential ability to produce mycotoxins was evaluated by PCR protocols which allow a rapid detection of OTA and FB 2 biosynthetic genes in their genomes. OTA production is not widespread in A. niger aggregate since only 17% of A. niger and 6% of A. welwitschiae isolates presented the complete biosynthetic cluster whereas the lack of the cluster was confirmed in all A. tubingensis isolates. On the other hand, A. niger and A. welwitschiae seem to be important FB 2 producers with 97% and 29% of the isolates, respectively, presenting the complete cluster. The genes involved in OTA and FB 2 were overexpressed in producing isolates and their expression was related to mycotoxin synthesis. • Aspergillus tubingensis is the most frequently isolated species in Spanish products. • Aspergillus tubingensis seems not to be able to produce ochratoxin A or fumonisin B 2. • Most Spanish A. niger and A. welwitschiae isolates are potential mycotoxin producers. [ABSTRACT FROM AUTHOR]