Aspergillus communities contaminating red chilies with aflatoxins
P. SINGH (1), P. Cotty (1) (1) University of Arizona, U.S.A.
Aflatoxins are carcinogenic, immunosuppressive metabolites that cause health concerns across the globe. Several Aspergilli have been implicated in aflatoxin contamination events with some aflatoxin-producers associated with specific crops. Red chilies (Capsicum spp.) are produced in warm regions that favor aflatoxin producers. Aflatoxin in red chilies may result in market loss and even crop destruction. In order to gain insight into causal agents of aflatoxin contamination of red chilies, naturally contaminated chilies from markets in Nigeria and the US were examined. The A. flavus L morphotype was the most frequently isolated member of Aspergillus section Flavi (89%). Fungi with S strain morphology were also detected in chilies from both countries (10%). Multi-gene phylogenetic analyses of partial gene sequences for nitrate reductase (niaD, 2.1 kb) and aflatoxin pathway transcription factor (aflR, 1.8 kb) resolved S morphotype fungi into three distinct clades. Fungi that produced only B aflatoxins formed a single clade with reference A. flavus regardless of L or S morphology. All S morphotype fungi from chilies purchased in Nigeria produced both B and G aflatoxins and were assigned to either A. minisclerotigenes or the previously described unnamed taxon SBG on the basis of phylogenetic affinities; over 60% of these fungi were assigned to A. minisclerotigenes. The results suggest the etiology of aflatoxin contamination of chili is complex and may vary with region.