Characterization of Aspergillis from dried red chilies (Capsicum spp.): Insights into the etiology of aflatoxin contamination

Authors: SINGH, PUMMI - University Of Arizona; Cotty, Peter

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/16/2019
Publication Date: 1/16/2019
Citation: Singh, P., Cotty, P.J. 2019. Characterization of Aspergillis from dried red chilies (Capsicum spp.): Insights into the etiology of aflatoxin contamination. International Journal of Food Microbiology. 289:145-153.

Interpretive Summary: Aflatoxins are carcinogenic fungal metabolites that contaminate dried red chilies (Capsicum spp.), one of the most consumed spices worldwide. Aflatoxin contamination of chilies results in dangerous exposure to the consumer and severe economic losses Characterization of the causal agents of contamination may facilitate development of procedures to prevent chili contamination. Red chilies were collected from markets across the United States and Nigeria and examined for aflatoxin-producing fungi. Taking into consideration both aflatoxin-producing potential and frequency of recovery, the most important causal agents of contamination were found to be fungi with S morphology. DNA based analyses suggested that these causal agents include two S morphology species previously unknown on chili. Non-native aflatoxin-producers were detected in chilies from US markets suggesting the need to prevent importation of exotic aflatoxins producers with chili. Results from the current study suggest that etiology of aflatoxin contamination of chilies may vary with region and that management should include measures directed at aflatoxin producers with S morphology.

Technical Abstract: Aflatoxins are toxic carcinogens produced by several species of Aspergillus section Flavi, with some aflatoxin producers associated with specific crops. Red chilies (Capsicum spp.)are grown in warm regions that also favor aflatoxin-producers. Aflatoxins in red chilies may result in serious health concerns and severe economic losses. The current study sought to gain insight on causal agents of aflatoxin contamination in red chilies. Naturally contaminated chilies from markets in Nigeria (n=55) and the United States (US) (n=169) were examined. The A. flavus L strain was the predominant member of Aspergillus section Flavi (84%) in chilies. Highly toxigenic fungi with S strain morphology were also detected in chilies from both countries (11%), followed by A. tamarii (4.6%) and A. parasiticus (0.4%). Fungi with L morphology produced significantly lower quantities of aflatoxins (mean = 43 µg g-1) compared to S morphology fungi (mean = 667 µg g-1; p < 0.01) in liquid fermentation. Eighty-one percent of S morphology fungi from chilies in US markets produced only B aflatoxins, whereas 20%, all imported from Nigeria, produced both B and G aflatoxins; all S morphology fungi from Nigerian chilies produced both B and G aflatoxins. Multi-gene phylogenetic analyses of partial gene sequences for nitrate reductase (niaD, 2.1 kb) and the aflatoxin pathway transcription factor (aflR, 1.9 kb) resolved Aspergilli recovered from chilies into five highly supported distinct clades: 1) A. parasiticus; 2) A. flavus with either L or S morphology; 3) A. minisclerotigenes; 4) previously reported unnamed taxon SBG erected as A. africanus sp. nov., and 5) a novel taxon erected as A. capsici sp. nov. Aspergillus capsici and A. africanus produced the highest concentrations of total aflatoxins in chilies, whereas A. flavus L strains produced the least. The results suggest etiology of aflatoxin contamination of chili is complex and may vary with region.