Ochratoxin production and taxonomy of the yellow aspergilli (Aspergillus section Circumdati)

Abstract

Aspergillus section Circumdati or the Aspergillus ochraceus group, includes species with rough walled stipes, biseriate conidial heads, yellow to ochre conidia and sclerotia that do not turn black. Several species are able to produce mycotoxins including ochratoxins, penicillic acids, and xanthomegnins. Some species also produce drug lead candidates such as the notoamides. A polyphasic approach was applied using morphological characters, extrolite data and partial calmodulin, β-tubulin and ITS sequences to examine the evolutionary relationships within this section. Based on this approach the section Circumdati is revised and 27 species are accepted, introducing seven new species: A. occultus, A. pallidofulvus, A. pulvericola, A. salwaensis, A. sesamicola, A. subramanianii and A. westlandensis. In addition we correctly apply the name A. fresenii (≡ A. sulphureus (nom. illeg.)). A guide for the identification of these 27 species is provided. These new species can be distinguished from others based on morphological characters, sequence data and extrolite profiles. The previously described A. onikii and A. petrakii were found to be conspecific with A. ochraceus, whilst A. flocculosus is tentatively synonymised with A. ochraceopetaliformis, despite extrolite differences between the two species. Based on the extrolite data, 13 species of section Circumdati produce large amounts of ochratoxin A: A. affinis, A. cretensis, A. fresenii, A. muricatus, A. occultus, A. ochraceopetaliformis (A. flocculosus), A. ochraceus, A. pseudoelegans, A. pulvericola, A. roseoglobulosus, A. sclerotiorum, A. steynii and A. westerdijkiae. Seven additional species produce ochratoxin A inconsistently and/or in trace amounts: A. melleus, A. ostianus, A. persii, A. salwaensis, A. sesamicola, A. subramanianii and A. westlandensis. The most important species regarding potential ochratoxin A contamination in agricultural products are A. ochraceus, A. steynii and A. westerdijkiae.