Submitted to: Soil Biology and Biochemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/18/2008
Publication Date: 1/19/2009
Citation: Donner, M., Atehnkeng, J., Sikora, R.A., Bandyopadhyay, R., Cotty, P.J. 2009. Distribution of Aspergillus section flavi in soils of maize fields in three agroecological zones of Nigeria. Soil Biology and Biochemistry. 41:37-44 Interpretive Summary: Aflatoxins are toxic fungal metabolites that can inhibit human development, cause cancer, and even induce death. Preventing the occurrence of these toxins in foods is very difficult, but of great concern in Nigeria. Identification of the causal agents of contamination and the distribution of these agents across environments is an important initial step in developing management programs. The current study determined the distribution of aflatoxin producing fungi across the major maize production regions of Nigeria and found that the most important causal agents vary with region. One very common aflatoxin producer, that has not been named as a formal species, is very common in Nigeria and unknown in the United States. Many atoxigenic strains of potential value in aflatoxin management were found. The results suggest different specific management strategies may be necessary in different regions of Nigeria and that efforts should be made to prevent movement of the high aflatoxin-producing, unnamed species from Nigeria to North America.
Technical Abstract: Fungal communities in soils of Nigerian maize fields were examined to determine distributions of aflatoxin-producing fungi and to identify endemic atoxigenic strains of potential value as biological control agents for limiting aflatoxin contamination in West African crops. Over 1,000 isolates belonging to Aspergillus section Flavi were collected from 55 Nigerian maize fields located in three agroecological zones by dilution plating soil onto modified Rose Bengal agar. The most common member of Aspergillus section Flavi (85% of isolates) was the A. flavus L-strain, followed by the unnamed taxon known as strain SBG (8%), A. tamarii (6%) and A. parasiticus (1%). Highest incidence of SBG was in the Zaria district, and the lowest was in the Ogbomosho and Ado-Ekiti districts. Only 44% of 492 A. flavus isolates tested produced aflatoxins (limit of detection 5 ppb). All tested SBG-and A. parasiticus isolates produced both B and G aflatoxins and greater than 310 thousand ppb total aflatoxins. The unnamed taxon SBG produced aflatoxin at up to 6.07 * 106 ng B1/g mycelium. Thirty two percent of the A. flavus isolates produced >1,000ppb aflatoxin B1. The most important aflatoxin producers varied by region. However, all regions had atoxigenic strains of potential value as biological control agents.