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POSTERS: Postharvest pathology and mycotoxins

Genetic diversity of Aspergillus flavus and identification of atoxigenic isolates to reduce aflatoxin contamination of chilies in Nigeria
Pummi Singh - University of Arizona. Kenneth Callicott- USDA ARS, Marc Orbach- University of Arizona

The filamentous fungus Aspergillus flavus is the primary cause of aflatoxin (AF) contamination of several crops in warm regions of the globe. Aflatoxins are of severe health and economic concern due to their toxicity and carcinogenicity. Red chili (Capsicum spp.), a widely produced and consumed spice in Nigeria is frequently contaminated by AFs. Aflatoxin contamination of chilies in Nigeria was previously attributed to A. aflatoxiformans, but knowledge of A. flavus genetic diversity associated with chilies and occurrence of atoxigenic isolates with potential for biological control of AF contamination remains unexplored. The current study examined the diversity and aflatoxigenicity of 325 A. flavus isolates recovered from Nigerian chilies (n=55) sampled in 2015-16. Isolates were diverse at 17 microsatellite loci, with 5 to 36 alleles per locus and 152 haplotypes. Among 120 haplotypes analyzed for aflatoxigenicity, 68 produced AFs (mean=75,365 ng/g) and 52 did not produce detectable concentrations of AFs (< 2 ng/g) on sterile maize. Isolates from 11 atoxigenic haplotypes had deletions in the AF cluster, which confirmed their inability to produce aflatoxins. Atoxigenic A. flavus isolates from chilies will be co-inoculated with toxigenic isolates to evaluate their potential to reduce AF concentrations in chilies. The atoxigenic isolates are a genetic resource for the development of biological control products for aflatoxin mitigation in chilies in Nigeria.