Aflatoxin contamination of maize and groundnut in Burundi: Distribution of contamination, indentification of casual agents and potential biocontrol genotypes of Aspergillus flavus

Authors: NSABIYUMVA, GEDEON - Institute Of Agronomic Sciences Of Burundi (ISABU); MUTEGI, CHARITY - International Institute Of Tropical Agriculture (IITA); WAGACHA, JOHN - University Of Nairobi; BAKARI, ASHA - International Institute Of Tropical Agriculture (IITA); NJERU, NANCY - Kenya Agricultural And Livestock Research Organization; NDAYIHANZAMASO, PRIVAT - Institute Of Agronomic Sciences Of Burundi (ISABU); NIYUHIRE, MARIE - Institute Of Agronomic Sciences Of Burundi (ISABU); ATEHNKENG, JOSEPH - International Institute Of Tropical Agriculture (IITA); NJUKWE, EMMANUEL - International Institute Of Tropical Agriculture (IITA); Callicott, Kenneth; COTTY, PETER - Ocean University Of China; ORTEGA-BELTRAN, ALEJANDRO - International Institute Of Tropical Agriculture (IITA); BANDYOPADHYAY, RANAJIT - International Institute Of Tropical Agriculture (IITA)

Submitted to: Frontiers in Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2023
Publication Date: 3/13/2023
Citation: Nsabiyumva, G., Mutegi, C.K., Wagacha, J.M., Bakari, A., Njeru, N., Ndayihanzamaso, P., Niyuhire, M.C., Atehnkeng, J., Njukwe, E., Callicott, K.A., Cotty, P.J., Ortega-Beltran, A., Bandyopadhyay, R. 2023. Aflatoxin contamination of maize and groundnut in Burundi: Distribution of contamination, indentification of casual agents and potential biocontrol genotypes of Aspergillus flavus. Frontiers in Microbiology. 2023. Article 1106543. https://doi.org/10.3389/fmicb.2023.1106543.
DOI: https://doi.org/10.3389/fmicb.2023.1106543

Interpretive Summary: Aflatoxins, carcinogens produced by the fungus Aspergillus flavus and its relatives, is a significant problem in sub-Saharan Africa. This study examines the extent of aflatoxin contamination in Burundi, genetically characterized populations of A. flavus associated with crops in Burundi and determined the potential of A. flavus isolates from Burundi to produce aflatoxins. A total of 380 maize and 120 groundnut samples were collected at harvest from relevant agricultural regions in Burundi. Most samples were safe for human consumption, but 50 maize samples and 8 groundnut samples contained enough aflatoxin to violate the European Union's standards. When individual A. flavus isolates were examined, the majority produced no aflatoxins, while others produced enough aflatoxin to represent a significant threat to human health. While aflatoxin doesn't appear to be a huge problem in crops at harvest, high aflatoxin producing isolates may present a significant risk during storage. Because of this risk, isolates that didn't produce aflatoxins were genetically characterized to find the most frequent genotypes in Burundi, under the assumption that frequent genetic types are successful. This analysis identified several common genotypes native to Burundi that hold promise for aflatoxin biocontrol as part of a larger aflatoxin control strategy.

Technical Abstract: Aflatoxin contamination of the staples maize and groundnut is a concern for health and economic impacts across sub-Saharan Africa. The current study i) determined aflatoxin levels in maize and groundnut collected at harvest in Burundi, ii) characterized populations of Aspergillus section Flavi associated with the two crops, and iii) assessed aflatoxin-producing potentials among the recovered fungi. A total of 120 groundnut and 380 maize samples were collected at harvest from eight and 17 provinces, respectively. Most of the groundnut (93%) and maize (87%) contained aflatoxin below the European Union threshold, 4 µg/kg. Morphological characterization of the recovered Aspergillus section Flavi fungi revealed that the L-morphotype of A. flavus was the predominant species. Aflatoxin production potentials of the L-morphotype isolates were evaluated in maize fermentations. Some isolates produced over 137,000 µg/kg aflatoxin B1. Thus, despite the relatively low aflatoxin levels at harvest, the association of both crops with highly toxigenic fungi poses significant risk of post-harvest aflatoxin contamination and suggests measures to mitigate aflatoxin contamination in Burundi should be developed. Over 55% of the L-morphotype A. flavus did not produce aflatoxins. These atoxigenic L-morphotype fungi were characterized using molecular markers. Several atoxigenic genotypes were detected across the country and could be used as biocontrol agents. The results from the current study hold promise for developing aflatoxin management strategies centered on biocontrol for use in Burundi to reduce aflatoxin contamination throughout the value chain.