Abstract
Aspergillus species associated with peanut kernel collected from Mecca, Madina, and Riyadh,Saudi Arabia were enumerated to assess the occurrence of aflatoxigenic species in these species. Also, a polymerase chain reaction (PCR) assay was optimized to identify two major toxigenic Aspergillus species, namely, Aspergillus flavus and Aspergillus niger collected from peanut seeds. Statistical data revealed the predominance of A. flavus (48%) and A. niger (42%) in sterilized seeds. Potential ability to produce aflatoxins (AFs) B1, B2, G1 and G2 was analyzed using high-performance liquid chromatography (HPLC). Among the 28 isolates analyzed, 21 produced aflatoxins, mainly B1 and B2. A. flavus isolates produced mainly aflatoxin B1 and had various levels of toxigenicity. Some isolates of A. flavus and A. niger produced aflatoxins B1, B2, G1 and G2 while others produced some aflatoxins with concentrations ranging from 1 to 7 ppm. The dendrogram showed that all aflatoxic isolates from the two species clustered together in the major cluster. A. niger (isolate no. 4) was classified into a single cluster that showed the lowest aflatoxin-producing ability. Specificity was tested in pure culture systems using DNA extracted from 28 Aspergillus isolates and five fungal species as PCR template. Aspergilli belonging to A. niger and the A. flavus group reacted positively, resulting in expected size amplicons of 796 bp for aflatoxin regulatory (aflR) primers and 500 bp for aflatoxin (FLA) primers, respectively. The suggested methods will be helpful in the detection and quantification of the toxigenic species A. flavus and A. niger in natural environments to forecast the toxin profiles which could be present in agricultural commodities.