Biodiversity of mycotoxigenic fungi: rapid and easy tools for identification of fungal diversity and detection of the related mycotoxin risk

Fungal biodiversity is one of the most important contributors to the occurrence and severity of mycotoxin contamination of crop plants. Phenotypic and metabolic plasticity has enabled mycotoxigenic fungi (MF) to colonize a broad range of agriculturally important crops and to adapt to a range of environmental conditions. New mycotoxin-commodity combinations provide evidence for the ability of fungi to adapt to changing conditions and the emergence of genotypes that confer enhanced aggressiveness toward plants and/or altered mycotoxin production profiles. Among diseases caused by MF, the most important are the result of attacks carried out by species complexes. Examples of these diseases are the Fusarium ear rot of maize, caused by species of the Fusarium fujikuroi species complex; Fusarium head blight of small-grain cereals (e.g. wheat, barley, and oat) caused by Fusarium graminearum species complex and a number of other Fusarium species; black point of wheat kernels caused by Alternaria alternata species complex and related species; grape rot caused by the black Aspergilli. Thus, the ability of various toxigenic species within the complexes to produce different classes of secondary metabolites, combined with their ability to coexist in the same host or/and occur in quick succession have allowed these complexes to become "invincible armadas" against many plants. Plant infections by MF can occur at all developmental stages, from germinating seeds to mature vegetative tissues, depending on the host plant and MF species involved. Therefore, since most toxigenic fungi have specific mycotoxin profiles, early and accurate identification of the species occurring in the plants at every step of their growth is critical to predict the potential toxicological risk to which plants are exposed and to prevent toxins entering the food chain. Moreover, the great biodiversity of MF species/strains is clearly the main factor responsible for the multi-toxin contamination risk in food commodities due to the co-occurrence of groups of toxigenic fungi genetically closely related or distant on the same crop. In addition, a great contribution to qualitative differences in mycotoxin production among fungi is variation in mycotoxin biosynthetic genes. We will report in the presentation main genetic, biochemical and chemical investigations carried out at the ISPA in order to: i) establish phylogenetic relatedness among the main species belonging to Alternaria, Aspergillus and Fusarium genera occurring on agro-food host plant products by using a multi-locus approach; ii) elucidate some specific differences in biosynthetic genes that are responsible for intra- and inter-specific differences in fumonisin and trichothecene production in Aspergillus and Fusarium, respectively; iii) develop rapid, easy and robust multi-mycotoxin detection methods for an accurate and reliable assessment of the risks related to the mycotoxin contamination of food products in the field.