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Aflatoxin producers in Mozambique include a distinct S morphology taxon with high capacity to produce aflatoxins in Maize and Groundnut

Lourena Arone: University of Arizona

<div>Aflatoxins are potent mycotoxins produced by several <em>Aspergillus</em> species. In Mozambique, aflatoxins prevent groundnuts from entering export markets and cause high rates of liver cancer. High frequencies of <em>Aspergillu</em>s with S morphology were discovered near Nampula, where human exposure to aflatoxins has been historically severe. To determine taxonomic affiliations of the Nampula fungi, phylogenetic analyses were applied to sequences from genome regions harboring genes for either the aflatoxin transcription factor (<em>aflR</em>, 1.8 kb), nitrate reductase (<em>niaD</em>, 2.2 kb), an MFS-transporter (<em>aflT</em>, 0.9 kb) or a cytochrome P450 monooxygenase (<em>cypA, 3.1 kb</em>). S morphology isolates (n = 448) were resolved into seven distinct taxa, with the majority (72%) clustering into a distinct and novel taxon sister to the previously described unnamed taxon S<sub>BG</sub>. Another distinct taxon, sister to the lethal aflatoxicosis fungi from Kenya, contained 20% of isolates while 8% were identified as <em>A. minisclerotigenes. </em>Although all S morphology fungi produced high aflatoxin concentrations, the newly discovered and most common taxon produced the highest aflatoxin concentrations (up to 62.5 mg/kg in maize and up to 17.6 mg/kg in groundnut); <em>A. minisclerotigenes</em> produced the lowest concentrations (up to 1.3 mg/kg in maize). Optimal selection of atoxigenic biocontrol agents should take into consideration effectiveness against the new taxa which are potent causal agents of aflatoxin contamination.</div>

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