Genetic diversity of Aspergillus flavus associated with chili in Nigeria and identification of haplotypes with potential in aflatoxin mitigation
Plant Dis. 2022 Jan 27. doi: 10.1094/PDIS-07-21-1464-RE. Online ahead of print.
Dried red chili (Capsicum spp.), a widely produced and consumed spice in Nigeria, is frequently contaminated by aflatoxins. Aflatoxins are potent mycotoxins of severe health and economic concern worldwide. Aspergillus flavus frequently contaminates crops with aflatoxins in warm regions; however, not all isolates are aflatoxin producers. Non-aflatoxigenic isolates have potential as biocontrol agents for aflatoxin mitigation. The current study examined the genetic diversity of A. flavus (n = 325) associated with chilies in Nigeria and identified 123 non-aflatoxigenic isolates. The Nigerian A. flavus isolates from chili were diverse at 17 microsatellite loci, with 5 to 36 alleles per locus, and included 152 haplotypes. The isolates that are active ingredients in Aflasafe, registered for aflatoxin biocontrol on maize and groundnuts in Nigeria, did not share haplotypes with the chili isolates. Of the 152 haplotypes, 65% produced aflatoxins in autoclaved maize, some of which (17%) produced more than 100,000 µg/kg of aflatoxins. Aflatoxins were not detected in 35% of the haplotypes. Cluster amplification pattern assay detected large deletion(s) in the aflatoxin biosynthetic clusters of some (32%) of the non-aflatoxigenic haplotypes. Co-infection of chili with non-aflatoxigenic isolates from chilies (n = 7) and A. aflatoxiformans resulted in a significantly greater average reduction in total aflatoxins compared to that achieved by Aflasafe active ingredient isolates (P < 0.01). These non-aflatoxigenic isolates are a genetic resource for the development of biological control products for aflatoxin mitigation in chilies in Nigeria and should be evaluated under field conditions.