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Diversity of Aspergillusspecies causing aflatoxin contamination of maize and groundnuts in Zambia
P. w. KACHAPULULA (1), R. Bandyopadhyay (2), J. Akello (3), M. Mukanga (4), P. J. Cotty (5). (1) Univ of Arizona, Tucson, AZ, U.S.A.; (2) IITA Nigeria, IBADAN, Nigeria; (3) IITA ZAMBIA, LUSAKA, Zambia; (4) Zambia Agricultural Research Institute, LUSAKA, Zambia; (5) Univ of Arizona/USDA-ARS, Tucson, AZ, U.S.A.

Aflatoxins are carcinogenic, immunosuppressive toxins that frequently contaminate maize and groundnut, important staples in Zambia. <i>Aspergillus</i> <i>flavus, A. parasiticus</i> and two unnamed taxa have been implicated as causal agents of aflatoxin contamination in Africa. Improved understanding of contamination etiology in Zambia may facilitate aflatoxin management. Maize, groundnut and soil from the three agroecologies of Zambia were examined from 2012 to 2013. Soils (125) and crops (188) were assayed for <i>Aspergillus</i> section <i>Flavi; </i>aflatoxins were quantified with lateral flow immunochromatographic assays. Many fungal communities were dominated by isolates morphologically assignable to <i>A. parasiticus</i>. Multi-gene phylogenetic analyses with partial gene sequences for nitrate reductase (<i>niaD</i>, 1.8 kb) and the aflatoxin pathway transcription factor (<i>aflR</i>, 2.1 kb) resolved 200 isolates with <i>A. parasiticus</i> morphology from across Zambia into five well supported lineages. All crop samples tested had at least 2 ppb total aflatoxin, with 8% and 4.7% of the samples above 10 ppb and 100 ppb respectively. Fungal community structures in soil and crops, differed. Soil communities were dominated by <i>A. parasiticus</i> (68%) while the <i>A. flavus</i> L-strain morphotype was highest in maize (61%) and fungi with S-strain morphology on groundnut (51%). Characteristics of the identified lineages and factors that underlie community structure within <i>Aspergillus</i> section <i>Flavi</i> are under investigation.

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