Aflatoxigenicity in Aspergillus species

Cultural, Molecular and Analytical Analysis

Abstract

Aflatoxins are some of the most harmful naturally occurring fungal metabolites that have been characterized. They are produced by certain species of fungi belonging to the genus Aspergillus. Due to the growing concern of exposure to aflatoxins, there has been a concerted effort to mitigate their harmful effects. One promising intervention is Biological Control (BC) where non-aflatoxigenic Aspergillus outcompete their aflatoxigenic relatives achieving a reduction in residual toxins. A prerequisite to the success of BC programs is the correct discrimination of aflatoxigenic isolates from non-aflatoxigenic. The current study assessed the aflatoxigenicity of previously isolated Aspergillus spp. native to the Eastern Kenya region (aflatoxin hotspot) with an aim of delineating aflatoxin-producers from non-producers. To determine aflatoxin production, a polyphasic approach, consisting of cultural, molecular and analytical methods was applied. Of the 314 fungi species isolated from maize kernels, a subset of 36 isolates taxonomically identified Aspergillus species was selected for this study. Through culture, Dichlorvos Ammonia (DV-AM) method revealed 52.8% of the isolates as aflatoxigenic while the rest were non-aflatoxigenic. The presence of 10 aflatoxin biosynthesis genes did not correlate with aflatoxigenicity. Furthermore, the aflatoxigenic potential of Aspergillus isolates in live culture was validated by ELISA. A positive correlation was observed between Live cultures and Dichlorvos-ammonia (p > 0.01), suggesting reliability of the two methods at discriminating aflatoxigenic from non-aflatoxigenic Aspergillus isolates. The present work confirms that a single method of analysis may not be sufficient at distinguishing aflatoxigenic from non-aflatoxigenic isolates, as compared to a combination of different approaches