Prevalence of NRRL21882-like (Afla-Guard^®) Aspergillus flavus on sesame seeds grown in research fields in the Mississippi Delta

ABSTRACT

A collection of 500 Aspergillus flavus isolates from four sesame varieties (S-34, S-35, S-38, and S-39) that were planted in field plots in the Mississippi Delta and in the Florida Panhandle were investigated because of low-level aflatoxin contamination detected in sesame seeds. A rapid molecular fingerprinting method was developed to assess the influence of prior applications of the atoxigenic Afla-Guard^® biocontrol product whose active strain is NRRL21882 on the A. flavus populations within each field plot. Depending on sesame seed sampled, 66.7% to 95.9% of A. flavus isolates from Mississippi belonged to the NRRL21882 genotype, which lacks the aflatoxin and cyclopiazonic acid biosynthesis gene clusters. In contrast, only 5.0% to 32.5% of the isolates from Florida had lost both gene clusters. The high incidence of NRRL21882-like A. flavus in Mississippi sesame samples can be attributed to prior applications of Afla-Guard^® in that local area. The results suggest the adaptability of this particular type of atoxigenic A. flavus biocontrol strain in the field.

KEYWORDS:

• Aspergillus flavus
• Afla-Guard
• NRRL21882
• sesame
• gene cluster
• biocontrol

Acknowledgements

We thank Kayla Gines, Jeremy Kotowicz, and Vivek Khambhati for technical assistance. Also we thank Dr. M. Mulvaney for providing sesame seed samples from Florida, University of Florida, Agronomy Department, Jay, Florida. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.

Disclosure statement

No potential conflict of interest was reported by the author(s).