Potential of Aflatoxin Production in Aspergillus Section Flavi Isolates of Pistachio in Iran

Aflatoxin analysis shows that Aspergillus section Flavi strains include mixtures of strains that are highly toxic to human with high level of aflatoxins while some others produce moderate level of aflatoxins and also there are nontoxigenic strains. 

To determine the aflatoxin producing abilities of Aspergillus section Flavi isolates in pistachio orchards, 180 pistachio nut samples were collected and fungal isolation was performed by Aspergillus Flavus and Parasiticus Agar (AFPA) medium. Distinct colony morphology in Coconut Agar Medium (CAM), Yeast Extract Sucrose (YES) medium supplemented with Methyl-β-cyclodextrin, and Sodium Low Salt (SLS) medium were used for distinguishing and screening between toxigenic and atoxigenic isolates. Toxigenicity and aflatoxins production level of isolates assayed by thin layer chromatography (TLC). 

One hundred and twenty isolates of various parts of the pistachio growing areas belonging to Aspergillus section Flavi was identified by AFPA. Out of 120 isolates, 89.15% were able to produce one or several types of aflatoxins while in 10.83% isolates there was no toxin production. Of isolates investigated in this study, 14.16% of total produced aflatoxins  were  B1, B2, G1, and G2, whereas 10.83% of the isolates produced B1, B2, and G1, 34.16% of the isolates produced B1 and B2, and only 30% of the isolates were able to produce B1 type aflatoxin. Generally, aflatoxin production between toxigenic isolates was in different ranges from 39-21548, 37-8432, 97-2111, and 31-810 ng/g for aflatoxin B1, B2, G1, and G2 respectively. 

 Out of 120 investigated isolates, 13 isolates produced no aflatoxins and toxigenicity of other isolates was potentially variable from very low to high level.