Molecular characterisation of Aspergillus flavus on imported maize through gazetted and ungazetted points of Entries in Kenya

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Research Paper 06/01/2024
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Molecular characterisation of Aspergillus flavus on imported maize through gazetted and ungazetted points of Entries in Kenya

Joseph Oduor Odongo, Paul O. Angi’enda, Bramwel Wanjala, Catherine Taracha, David M. Onyango
Int. J. Micro. Myco.18( 1), 1-22, January 2024.
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Abstract

Maize is a vital staple crop in Kenya, serving as a primary source of food and feed. Contamination of maize (Zea mays) by Aspergillus flavus  and the subsequent production of aflatoxins pose significant threats to food safety and human health. The risk of A. flavus contamination on imported maize at both gazetted and un-gazetted points of entry has not been extensively studied. The primary objective of this study was to examine the genotypic, phenotypic, and aflatoxigenic traits of A. flavus biovars derived from imported maize at Gazetted and Un-gazetted Points of Entries in Kenya. Furthermore, the study sought to establish the phylogenetic relationships among the identified A. flavus strains. A total of 600 imported maize samples were tested for aflatoxin contamination using the Total aflatoxin ELISA test. Out of 600 samples, 4.17% tested positive and were further subjected to morphological and molecular studies.  The morphological analysis revealed the presence of 13 biovars of A. flavus. Micro-morphologically, variations were observed in spore color, size, structure, conidiophore structure, and vesicle shape. The specific primers Calmodulin (CaM), the ITS1-5.8S-ITS2 region of the ribosomal DNA was successfully amplified in 10 out of the 13 biovars that were presumed to be A. flavus, confirming their positive identification as A. flavus. A single band of approximately 700 bp, which corresponds to the expected size of the ITS region in Aspergillus flavus, was observed in 10 out of the 13 biovars. This indicates the presence of A. flavus DNA in those biovars. The amplification of the ITS region provides a specific molecular marker for the identification of A. flavus. These findings highlight the significance of aflQ (ordA) and aflD (nor-1) genes as reliable markers for evaluating the aflatoxigenic potential of A. flavus biovars. Regarding aflatoxigenicity, DV-AM   method was used, and qualitative analysis was conducted. Out of the 13 biovars of A. flavus biovars tested, 23.08% exhibited aflatoxigenicity, while the remaining 10 biovars did not show any aflatoxigenicity. These findings indicate the presence of both aflatoxigenic and non-aflatoxigenic strains of A. flavus among the imported maize samples. The phylogenetic analysis revealed that Taxon 31 (AY495945.1 Aspergillus flavus biovar 92016f aflR-aflJ intergenic region partial sequence) and Taxon 32 (NR 111041.1 Aspergillus flavus ATCC 16883 ITS region from TYPE material). This genotypic and phenotypic characterization provides valuable information for understanding the diversity and potential toxigenicity of A. flavus strains on imported maize. This study contributes to the understanding of the genotypic and phenotypic characteristics of A. flavus on imported maize in Kenya.

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