Dual culture of atoxigenic and toxigenic strains of Aspergillus flavus to gain insight into repression of aflatoxin biosynthesis and fungal interaction

  • Sui Sheng T. HuaEmail author
  • Dan E. Parfitt
  • Siov Bouy L. Sarreal
  • Gaganjot Sidhu
Original Article


Application of atoxigenic strains to compete against toxigenic strains of Aspergillus flavus strains has emerged as one of the practical strategies for reducing aflatoxin contamination in corn, peanut, and tree nuts. The actual mechanism that results in aflatoxin reduction is not fully understood. Real-time RT-PCR and relative quantification of gene expression protocol were applied to elucidate the molecular mechanism. Transcriptional analyses of aflatoxin biosynthetic gene cluster in dual culture of toxigenic and atoxigenic A. flavus strains were carried out. Six targeted genes, aflR, aflJ, omtA, ordA, pksA, and vbs, were downregulated to variable levels depending on paired strains of toxigenic and atoxigenic A. flavus. Consistent with the decreased gene expression levels, the aflatoxin concentrations in dual cultures were reduced significantly in comparison with toxigenic cultures. Fluorescent images showed fungal hyphae in dual culture displayed green fluorescent, and contacts of live hyphae were seen. A coconut agar plate assay was used to show that toxigenic A. flavus colony produced blue fluorescence under long UV exposure, suggesting that aflatoxin is exported outside fungal hyphae. Furthermore, the assay was applied to demonstrate the potential role of thigmo-regulation in fungal interaction.


Biocontrol Aflatoxin Gene regulation Aspergillus flavus Food safety 


Funding information

This work is supported by in-house research program funds from U.S. Department of Agriculture, Agricultural Research Services (Project Numbers: 5325-42000-039-00D).

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflicts of interest.

Supplementary material

12550_2019_364_MOESM1_ESM.xlsx (17 kb)
ESM 1 (XLSX 16 kb)


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Copyright information

© This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply 2019

Authors and Affiliations

  • Sui Sheng T. Hua
    • 1
    Email author
  • Dan E. Parfitt
    • 2
  • Siov Bouy L. Sarreal
    • 1
  • Gaganjot Sidhu
    • 1
  1. 1.U.S. Department of Agriculture, Agricultural Research ServiceWestern Regional Research CenterAlbanyUSA
  2. 2.Department of Plant SciencesUniversity of California, DavisDavisUSA

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