Poster: Biology & Disease Mgmt: Biological Control
Relative efficacy of Zambian atoxigenic Aspergillus flavus strains against aflatoxin-producing Aspergillus species
J. AKELLO (1), T. Dubois (2), J. Atehnkeng (3), M. Mukanga (4), H. Njapau (5), J. Augusto (6), P. Cotty (7), R. Bandyopadhyay (3) (1) International Institute of Tropical Agriculture (IITA-Zambia), Zambia; (2) The World Vegetable Center (AVRDC) Eastern and
In Zambia, fields cropped to maize and groundnuts are predominantly colonized by aflatoxin producing Aspergillus flavus S-morphotypes and A. parasiticus. Consequently, Zambian staple foods are often contaminated with high aflatoxin levels (>20 ppb) while in the field and during storage. This study aimed at identifying the best atoxigenic A. flavus L-strains for use as biocontrol agents. In vitro, the most toxigenic L (25) and SBG (10) strains were selected out of the entire isolate library based on qualitative and quantitative TLC assessment. Competition assays were performed by co-inoculating 14 atoxigenic candidate strains and the 35 selected toxigenic ones on sterile maize grains in sterile vials. All the 14 atoxigenic strains outcompeted the toxigenic ones and reduced aflatoxin production by >96% in vitro. Eight of the 14 atoxigenic strains were selected and formulated into two mixes, with each mix comprising of 4 strains. Each mix was applied to maize and groundnut fields between 2012 and 2015 at a rate of 10 kg/ ha, 2-3 weeks before flowering. Treating fields with the two mixes altered Aspergillus soil community structure and significantly reduced aflatoxin levels in maize and groundnuts by 89.6% compared to untreated ones. Thus, the 8 atoxigenic strains hold promise for fighting aflatoxin burden in maize and groundnut. Adopting such strains to address aflatoxin could improve grain nutritional quality and safety for better health of the Zambian populace.