Taxonomy ofAspergillussectionFlaviand their production of aflatoxins, ochratoxins and other mycotoxins

Abstract

Aflatoxins and ochratoxins are among the most important mycotoxins of all and producers of both types of mycotoxins are present in Aspergillus section Flavi, 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 section Flavi. Phylogenetically, section Flavi is split in eight clades and the section currently contains 33 species. Two species only produce aflatoxin B1 and B2 (A. pseudotamarii and A. togoensis), and 14 species are able to produce aflatoxin B1, B2, G1 and G2: three newly described species A. aflatoxiformans, A. austwickii and A. cerealis in addition to A. arachidicola, A. minisclerotigenes, A. mottae, A. luteovirescens (formerly A. bombycis), A. nomius, A. novoparasiticus, A. parasiticus, A. pseudocaelatus, A. pseudonomius, A. sergii and A. transmontanensis. It is generally accepted that A. flavus is unable to produce type G aflatoxins, but here we report on Korean strains that also produce aflatoxin G1 and G2. One strain of A. bertholletius can produce the immediate aflatoxin precursor 3-O-methylsterigmatocystin, and one strain of Aspergillus sojae and two strains of Aspergillus alliaceus produced versicolorins. Strains of the domesticated forms of A. flavus and A. parasiticus, A. oryzae and A. sojae, respectively, lost their ability to produce aflatoxins, and from the remaining phylogenetically closely related species (belonging to the A. flavus-, A. tamarii-, A. bertholletius- and A. nomius-clades), only A. caelatus, A. subflavus and A. tamarii are unable to produce aflatoxins. With exception of A. togoensis in the A. coremiiformis-clade, all species in the phylogenetically more distant clades (A. alliaceus-, A. coremiiformis-, A. leporis- and A. avenaceus-clade) are unable to produce aflatoxins. Three out of the four species in the A. alliaceus-clade can produce the mycotoxin ochratoxin A: A. alliaceus s. str. and two new species described here as A. neoalliaceus and A. vandermerwei. Eight species produced the mycotoxin tenuazonic acid: A. bertholletius, A. caelatus, A. luteovirescens, A. nomius, A. pseudocaelatus, A. pseudonomius, A. pseudotamarii and A. tamarii while 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. sergii and A. tamarii. Furthermore, A. hancockii produced speradine A, a compound related to cyclopiazonic acid. Selected A. aflatoxiformans, A. austwickii, A. cerealis, A. flavus, A. minisclerotigenes, A. pipericola and A. sergii strains produced small sclerotia containing the mycotoxin aflatrem. Kojic acid has been found in all species in section Flavi, except A. avenaceus and A. coremiiformis. Only six species in the section did not produce any known mycotoxins: A. aspearensis, A. coremii...

Discrimination of Aspergillus flavus from Aspergillus oryzae by matrix‐assisted laser desorption/ionisation time‐of‐flight (MALDI‐TOF) mass spectrometry

“…6 Conventional identification approaches, including microscopic and macroscopic characterization, have been unable to discriminate between these closely related species. 6 Furthermore, a high degree of…”

“…The taxonomy of this section is complex and is currently under development . A large number of species in section Flavi are commonly observed plant pathogens producing several mycotoxins . The six economically important species in the section, A flavus , A parasiticus , A nomius , A oryzae , A sojae and A tamarii , are morphologically and phylogenetically very closely related; among them, A oryzae and A sojae are extensively used in the food and biotechnology industries .…”

“…A large number of species in section Flavi are commonly observed plant pathogens producing several mycotoxins . The six economically important species in the section, A flavus , A parasiticus , A nomius , A oryzae , A sojae and A tamarii , are morphologically and phylogenetically very closely related; among them, A oryzae and A sojae are extensively used in the food and biotechnology industries . Conventional identification approaches, including microscopic and macroscopic characterization, have been unable to discriminate between these closely related species .…”

“…The six economically important species in the section, A flavus , A parasiticus , A nomius , A oryzae , A sojae and A tamarii , are morphologically and phylogenetically very closely related; among them, A oryzae and A sojae are extensively used in the food and biotechnology industries . Conventional identification approaches, including microscopic and macroscopic characterization, have been unable to discriminate between these closely related species . Furthermore, a high degree of DNA relatedness among A flavus , A oryzae , A parasiticus and A sojae isolates has been reported, which further hampers the application of molecular approaches for their discrimination from each other …”

Aflatoxins: Production, Structure, Health Issues and Incidence in Southeast Asian and Sub-Saharan African Countries

“…The production of aflatoxins has been reported in members of three sections of Aspergillus genus; section Flavi (B-and G-type aflatoxins), section Ochraceorosei (aflatoxins B1 and B2), and section Nidulantes (formerly Emericella genus; aflatoxin B1) [8]. However, species of section Flavi are the most common and potent aflatoxin-producing moulds, with A. flavus and A. parasiticus being the most frequently encountered in agricultural products because of their widespread distribution in the agricultural environment and their versatility to grow and produce aflatoxins under different ecological conditions [9][10][11]. A recent classification based on a polyphasic approach revealed that 18 species out of 33 of the section Flavi are aflatoxigenic and that each of 16 species is able to produce the 4 major aflatoxins (AFB1, AFB2, AFG1, and AFG2), while the other 2 species produce either AFB1 alone (A. togoensis) or both AFB1 and AFB2 (A. pseudotamarii) [11] (Table 1).…”