Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/19/2010
Publication Date: 2/1/2011
Citation: Probst, C., Bandyopadhyay, R., Price, L.E., Cotty, P.J. 2011. Identification of atoxigenic Aspergillus flavus isolates to reduce aflatoxin contamination of maize in Kenya. Plant Disease. 95(2):212-218. Interpretive Summary: Aflatoxins are toxic fungal metabolites that can inhibit human development, cause cancer, and even induce death. Aflatoxin contamination of maize is a recurring problem in Kenya. Consumption of contaminated maize killed several hundred people in 2004. Use of strains of Aspergillus flavus that do not produce aflatoxins to competitively exclude aflatoxin-producers has become widely accepted as a useful component of aflatoxin management programs. The current study sought to determine if atoxigenic Aspergillus flavus isolates existed within the highly toxic fungal communities distributed in the regions of Kenya that experienced deaths due to aflatoxins. Native Kenyan atoxigenic Aspergillus flavus isolates were identified and found to be capable of competitively excluding aflatoxin producers during maize infection and as a result reduce aflatoxin contamination. Aflatoxin reduction potential of the identified isolates exceeded 80% in laboratory assays. Over 40 atoxigenic strains native to Kenya and of potential value as biological control agents were characterized in the current study. These isolates are endemic to Kenya and, as a result, they are more likely than introduced isolates both to be well adapted to East African environments and to meet regulatory concerns over their use in Africa. What is the problem being addressed? Aflatoxins are poisonous metabolites of fungi that may contaminate several crops. The goal of the current study was to identify and characterize native atoxigenic Aspergillus flavus isolates that are able to competitively exclude toxigenic isolates on maize in Kenya. What was the impact? Native Kenyan atoxigenic Aspergillus flavus isolates have been identified and characterized as potential biocontrol agents for aflatoxicosis prone regions in the Eastern Province of Kenya. Aflatoxin reduction potential of the identified isolates exceeds 80% in laboratory assays.
Technical Abstract: Acute aflatoxin poisonings (aflatoxicosis) in Kenya have led to the deaths of several hundred people between 2004 and 2006. Etiology of contamination in the outbreak districts (Eastern Province) identified an unusual fungal community structure dominated by the highly toxigenic Aspergillus flavus S strain. Biocontrol strategies to reduce aflatoxins in maize and prevent further human fatalities are urgently needed. The objectives of our study were to identify and characterize atoxigenic A. flavus L strain isolates from three maize producing Kenyan Provinces (Eastern, Rift Valley and Coast) and to test their potential to competitively reduce aflatoxins on maize. Aflatoxin-producing potential of 290 Kenyan L strain isolates was tested resulting in the identification of 96 atoxigenic isolates. Competitive exclusion experiments of all atoxigenic isolates with a high aflatoxin-producing Kenyan S strain isolate has identified potential biological control strains able to reduce aflatoxins up to 90%. Additionally, we identified major atoxigenic vegetative compatibility groups (VCGs) containing up to 10 isolates endemic in one, two or all Kenyan Provinces. Identification of biological control agents able to revive natural competition and therefore reducing aflatoxins in maize in Eastern Kenya are first steps in implementing successful aflatoxin management strategies. Field experiments within Kenya to test isolates abilities to compete in natural settings are recommended.