Aflatoxin formation and the dual phenomenon in Aspergillus flavus Link.
Trials were performed with three aflatoxin-forming isolates of Aspergillus flavus from formic acid-treated materials containing aflatoxin, one A. flavus strain isolated from mouldy barley kept for two months in an anaerobic jar and one non-toxic A. flavus strain from the culture collection at our Department. The non-toxic strain and one aflatoxin producer were cultured in salts-sugar-asparagine substrate (SLM) for aflatoxin production and in a specially prepared grass substrate (GS). Formic acid and ammonium formate were added to both substrates, and sucrose in a low amount was added to the grass substrate. The aflatoxin-forming isolate segregated on the grass substrate into two different lines, one with high aflatoxin production and one with very low aflatoxin-forming ability, higher growth rate and reduced sporulation, on the SLM substrate. When exposed to sucrose in grass substrate and ammonium formate in SLM, one toxic and one non-toxic strain were provoked to increased aflatoxin formation. The A. flavus isolate from the anaerobic jar also segregated on the grass substrate, and these segregants were more sensitive to a high dose of formic acid. In these A. flavus strains three seems to be a continuous variation between different lines, depending on cultivation conditions. In the two aflatoxin-forming isolates left, such segregation tendencies were not very marked on any substrate.
D016604:Aflatoxin B1; D000348:Aflatoxins / Q000096:biosynthesis*; D001231:Aspergillus flavus / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D003470:Culture Media; D005453:Fluorescence; D005561:Formates / Q000378:metabolism; D011753:Pyrones / Q000096:biosynthesis
D000348:Aflatoxins; D003470:Culture Media; D005561:Formates; D011753:Pyrones; C027955:aflatoxin G1; C029754:aflatoxin G2; C011890:kojic acid; C029753:aflatoxin B2; D016604:Aflatoxin B1