Location: Food and Feed Safety ResearchTitle: Deciphering the origin of Aspergillus flavus NRRL21882, the active biocontrol agent of Afla-Guard®
|Chang, Perng Kuang
|CHANG, THOMAS - Consultant
|KATOH, KAZUTAKA - University Of Osaka
Submitted to: Letters in Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2020
Publication Date: 11/29/2020
Citation: Chang, P.-K., Chang, T.D., Katoh, K. 2020. Deciphering the origin of Aspergillus flavus NRRL21882, the active biocontrol agent of Afla-Guard®. Letters in Applied Microbiology. 72:509-516. https://doi.org/10.1111/lam.13433.
Interpretive Summary: Aspergillus flavus populations are genetically diverse. Toxigenic A. flavus infects crops and produces aflatoxin, which is a great threat to human and animal health. On the contrary, non-aflatoxigenic A. flavus is currently being used as a biocontrol agent. Their close relative, Aspergillus oryzae, has been widely used in food fermentation for centuries. In this work, the evolutionary origin of A. flavus NRRL21882, the active strain of the biocontrol product Afla-Guard®, was revealed and its close relatives were identified in field A. flavus populations. This study provides a better understanding of genome similarity and dissimilarity between A. flavus and A. oryzae. Information obtained should assist selection and characterization of non-aflatoxigenic A. flavus strains for effective biocontrol.
Technical Abstract: Single nucleotide polymorphisms (SNPs) of genome sequences of eight Aspergillus flavus and seven Aspergillus oryzae strains were extracted with Mauve, a multiple-genome alignment program. A phylogenetic analysis with sequences comprised of concatenated total SNPs by the unweighted pair group method with arithmetic mean (UPGMA) of MAFFT adequately separated them into three groups, A. flavus S-morphotype, A. flavus L-morphotype, and A. oryzae. Divergence time inferred for A. flavus NRRL21882, the active agent of the biocontrol product Afla-Guard®, and S-morphotype was about 5.1 mya. Another biocontrol strain, A. flavus AF36, diverged from aflatoxigenic L-morphotype about 2.6 to 3.0 mya. Despite the close relatedness of A. oryzae to A. flavus, A. oryzae strains likely were evolved from aflatoxigenic Aspergillus aflatoxiformans (=A. parvisclerotigenus). A survey of A. flavus populations implies that prior Afla-Guard® applications are associated with prevalence of NRRL21882-type isolates in Mississippi fields. In addition, a few NRRL21882-like relatives were identified. A. flavus Og0222, a biocontrol ingredient of Aflasafe™, was verified as a NRRL21882-type strain, which had identical sequence breakpoints that led to deletion of aflatoxin and cyclopiazonic acid gene clusters. A similar UPGMA analysis suggests that the occurrence of NRRL21882-type strains is a more recent event.