Taxonomy of Aspergillus section Flavi and their production of aflatoxins, ochratoxins and other mycotoxins

Aflatoxins and ochratoxins are among the most important mycotoxins of all and producers of both types of mycotoxins are present inAspergillussectionFlavi, albeit never in the same species. Some of the most efficient producers of aflatoxins and ochratoxins have not been described yet. Using a polyphasic approach combining phenotype, physiology, sequence and extrolite data, we describe here eight new species in sectionFlavi. Phylogenetically, sectionFlaviis split in eight clades and the section currently contains 33 species. Two species only produce aflatoxin B1 and B2 (A. pseudotamariiandA. togoensis), and 14 species are able to produce aflatoxin B1, B2, G1 and G2: three newly described speciesA. aflatoxiformans, A. austwickiiandA. cerealisin addition toA. arachidicola,A. minisclerotigenes,A. mottae, A. luteovirescens(formerlyA. bombycis), A. nomius, A. novoparasiticus, A. parasiticus, A. pseudocaelatus, A. pseudonomius, A. sergiiandA. transmontanensis. It is generally accepted thatA. flavusis unable to produce type G aflatoxins, but here we report on Korean strains that also produce aflatoxin G1 and G2. One strain ofA. bertholletiuscan produce the immediate aflatoxin precursor 3-O-methylsterigmatocystin, and one strain ofAspergillus sojaeand two strains ofAspergillus alliaceusproduced versicolorins. Strains of the domesticated forms ofA. flavusandA. parasiticus,A. oryzaeandA. sojae, respectively, lost their ability to produce aflatoxins, and from the remaining phylogenetically closely related species (belonging to theA. flavus-,A. tamarii-,A. bertholletius- andA. nomius-clades), onlyA. caelatus,A. subflavusandA. tamariiare unable to produce aflatoxins. With exception ofA. togoensisin theA. coremiiformis-clade, all species in the phylogenetically more distant clades (A. alliaceus-,A. coremiiformis-,A. leporis- andA. avenaceus-clade) are unable to produce aflatoxins. Three out of the four species in theA. alliaceus-clade can produce the mycotoxin ochratoxin A:A. alliaceus s.str. and two new species described here asA. neoalliaceusandA. vandermerwei. Eight species produced the mycotoxin tenuazonic acid:A. bertholletius,A. caelatus, A. luteovirescens,A. nomius, A. pseudocaelatus,A. pseudonomius, A. pseudotamariiandA. tamariiwhile the related mycotoxin cyclopiazonic acid was produced by 13 species:A. aflatoxiformans, A. austwickii, A. bertholletius, A. cerealis, A. flavus, A. minisclerotigenes, A. mottae, A. oryzae, A. pipericola, A. pseudocaelatus,A. pseudotamarii, A. sergiiandA. tamarii. Furthermore,A. hancockiiproduced speradine A, a compound related to cyclopiazonic acid. SelectedA. aflatoxiformans, A. austwickii, A. cerealis, A. flavus, A. minisclerotigenes, A. pipericolaandA. sergiistrains produced small sclerotia containing the mycotoxin aflatrem. Kojic acid has been found in all species in sectionFlavi, exceptA. avenaceusandA. coremiiformis. Only six species in the section did not produce any known mycotoxins:A. aspearensis,A. coremiiformis, A. lanosus, A. leporis, A. sojaeandA. subflavus. An overview of other small molecule extrolites produced inAspergillussectionFlaviis given.