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

Authors: Chang, Perng Kuang; Scharfenstein, Leslie; Abbas, Hamed; Bellaloui, Nacer; ACCINELLI, CESARE - University Of Bologna, Italy; EBELHAR, M - Delta Research & Extension Center

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/30/2020
Publication Date: 7/13/2020
Citation: Chang, P.-K., Scharfenstein, L.L., Abbas, H.K., Bellaloui, N., Accinelli, C., Ebelhar, M.W. 2020. Prevalence of NRRL21882-like (Afla-Guard®) Aspergillus flavus on sesame seeds grown in research fields in the Mississippi Delta. Biocontrol Science and Technology. 30:1090-1099. https://doi.org/10.1080/09583157.2020.1791798.
DOI: https://doi.org/10.1080/09583157.2020.1791798

Interpretive Summary: Sesame is one of the earliest oilseed plants and has been cultivated for more than 5,000 years. The high quality contents of oleic acid and linoleic acid of sesame seeds have gained increasing attention because of their health benefits. Oil-rich crops are susceptible to fungal infection, particularly by the aflatoxin-producing Aspergillus flavus. In the United States, aflatoxin contamination of sesame seeds grown in Mississippi is only sporadic, and levels detected do not impact human and animal health significantly. In this study, we investigated possible causes of this low aflatoxin contamination of sesame seeds grown in Mississippi. It appears that prior applications of the biocontrol product Afla-Guard®, of which the active strain is atoxigenic A. flavus NRRL21882, in the same region greatly increased infection of sesame seeds by this particular type of fungal strain. This fact may in part contribute to the low levels of aflatoxin contamination of sesame seeds during 2014 and 2015.

Technical 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. 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-type A. flavus in Mississippi sesame samples can be attributed to prior applications of Afla-Guard® in that region. The results suggest the tenacious survivability of this particular type of atoxigenic A. flavus biocontrol strain in the field.