Mycotoxin-producing ability and chemotype diversity of Aspergillus section flavi from soils of peanut-growing regions in iran.

Invasion of crops with Aspergillus flavus may result in contamination of food and feed with carcinogenic mycotoxins such as aflatoxins (AF) and cyclopiazonic acid (CPA). In the present study, distribution and toxigenicity of Aspergillus flavus and A. parasiticus in soils of five peanut fields located in Guilan province, Northern Iran was investigated. From a total of 30 soil samples, 53 strains were isolated which all of them were finally identified as A. flavus by a combination of colony morphology, microscopic criteria and mycotoxin profiles. Chromatographic analysis of fungal cultures on yeast extract sucrose broth by tip culture method showed that 45 of the 53 A. flavus isolates (84.9 %) were able to produce either CPA or AFB1, while eight of the isolates (15.1 %) were non-toxigenic. The amounts of CPA and AFB1 produced by the isolates were reported in the range of 18.2-403.8 μg/g and 53.3-7446.3 μg/g fungal dry weights, respectively. Chemotype classification of A. flavus isolates based on the ability for producing mycotoxins and sclerotia showed that 43.4 % were producers of CPA, AFB1 and sclerotia (group I), 13.2 % of CPA and AFB1 (group II), 9.4 % of AFB1 and sclerotia (group III), 13.2 % of AFB1 (group IV), 5.7 % of CPA and sclerotia (group V) and 15.1 % were non-toxigenic with no sclerotia (group VI). No strain was found as producer of only CPA or sclerotia. These results indicate different populations of mycotoxigenic A. flavus strains enable to produce hazardous amounts of AFB1 and CPA are present in peanuts field soils which can be quite important regard to their potential to contaminate peanuts as a main crop consumed in human and animal nutrition.