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Title: Field efficacy of a mixture of atoxigenic Aspergillus flavus Link:Fr vegetative compatibility groups in preventing aflatoxin contamination in maize (Zea mays L.)

Author
item ATEHNKENG, J - International Institute Of Tropical Agriculture (IITA)
item OJIAMBO, P - North Carolina State University
item Cotty, Peter
item BANDYOPADHYAY, R - International Institute Of Tropical Agriculture (IITA)

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2014
Publication Date: 2/22/2014
Citation: Atehnkeng, J., Ojiambo, P.S., Cotty, P.J., Bandyopadhyay, R. 2014. Field efficacy of a mixture of atoxigenic Aspergillus flavus Link:Fr vegetative compatibility groups in preventing aflatoxin contamination in maize (Zea mays L.). Biological Control. 72:62-70.

Interpretive Summary: Aflatoxins are toxic fungal metabolites that can inhibit human development, induce cancer, impair the immune system, and, at high concentrations, cause rapid death. Preventing the occurrence of these toxins in foods is a high priority for efforts to ensure food security in Africa where human populations are chronically exposed to dangerous aflatoxin concentrations. Use of atoxigenic strains of Aspergillus flavus that do not produce aflatoxins to competitively exclude aflatoxin-producers has become widely accepted as the most effective component of aflatoxin management programs. A biocontrol tool based on four atoxigenic strains native to Nigeria was developed for use in preventing aflatoxin contamination of maize and groundnut in that nation. In order to advance the biocontrol to practical use in Nigeria, efficacy trials were performed at four experiment stations over two years. During the field trials the Nigerian atoxigenic strain biocontrol product provided 67 to 95% reductions in aflatoxin content when compared with untreated controls. The results will support experimental pesticide registration for evaluation of the biocontrol in farmer’s fields in portions of Nigeria with high incidences of aflatoxins. Dates of Research: May 2007 until December 2010. All reviewers comments were incorporated into revisions, but the collaborators submitted after clearing their system. This paper has also been reviewed and accepted for publication by the peer review system of the International Institute of Tropical Agriculture (IITA). Target Journal: Biological Control

Technical Abstract: Competitive exclusion of aflatoxin producers by endemic atoxigenic strains of Aspergillus flavus is a proven tool for aflatoxin management being adapted for use in Africa. Field efficacy of an experimental formulation consisting of four native atoxigenic strains (La3303, La3304, La3279 and Ka16127) was evaluated on maize in 2007 and 2008 in four agroecological zones in Nigeria. The four atoxigenic strains were individually formulated on sterile sorghum grain and subsequently mixed in equal proportions. The blended product was applied on soil (40 kg/ha), 2 to 3 weeks before flowering. Grains from treated and untreated fields were analyzed for aflatoxins at harvest and after storage. Proportions of the A. flavus population composed of each of the four applied strains in soil before treatment and in harvested grains were determined using vegetative compatibility analyses. Application of the strain mixture resulted in reduced aflatoxin content and significantly (P < 0.05) increased the combined frequencies of the vegetative compatibility groups (VCGs) of the applied strains recovered from the soil and grain. Aflatoxin reductions of 67 to 95% were associated with a 74 to 80% combined incidence of the VCGs of the four atoxigenic strains on the treated crops. The applied atoxigenic strains remained with the crop into storage and reduced postharvest increases in contamination. The results suggest that the evaluated multi-strain formulated product has potential to contribute to reduced aflatoxin contamination in Nigeria. This is the first report of a field evaluation of an endemic strain mixture effective at reducing aflatoxin contamination during crop development.