Fusarium graminearum virus-1 strain FgV1-SD4 infection eliminates mycotoxin Deoxynivalenol synthesis by F. graminearum in FHB

Authors: PAUDEL, BIMAL - South Dakota State University; Pedersen, Connar; YEN, YANG - South Dakota State University; Marzano, Shin-Yi

Submitted to: Microorganisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/13/2022
Publication Date: 7/23/2022
Citation: Paudel, B., Pedersen, C.J., Yen, Y., Marzano, S.L. 2022. Fusarium graminearum virus-1 strain FgV1-SD4 infection eliminates mycotoxin Deoxynivalenol synthesis by F. graminearum in FHB. Microorganisms. 10: Article 1484. https://doi.org/10.3390/microorganisms10081484.
DOI: https://doi.org/10.3390/microorganisms10081484

Interpretive Summary: Since F. graminearum is one of the worst pathogens of small grain crops, viruses that can make it hypovirulent and reduce the level of deoxynivalenol (DON) are of keen interest for their potential application as biocontrol agents. The novel strain of a mycovirus, Fusarium graminearum virus 1, FgV1-SD4, makes F. graminearum hypovirulent; however, the Chinese strain FgV1-ch does not. Narrowing down the hypovirulence determinant(s) for this virus to disarm virus-free strains has a great scope for understanding the arms race between the mycovirus and the pathogenic F. graminearum. Here, we share results of our efforts to cure this virus by single conidial germination and to speculate how FgV1 infection down-regulates DON biosynthesis in F. graminearum.

Technical Abstract: In this study, we confirmed the infection of a novel strain of Fusarium graminearum virus 1, FgV1-SD4, discovered by metatranscriptome. More importantly, we validated its role in hypovirulence of F. graminearum comparing to the same isolate without the mycovirus infection, and in eliminating the accumulation of mycotoxin, DON, in the infected grains. The observed total elimination of DON from wheat grains infected by F. graminearum strain carrying FgV1-SD4 is very promising for further development of this mycovirus as a potential biocontrol agent. Strain Fg-4 might have had very low titer of FgV1-SD4 virus but when it was sub-cultured multiple times, viral titer gradually increased thus making the strain Fg-4-2 hypovirulent compared to the original frozen stock. Freezing followed by single conidial germination allowed us to recover a virus free culture of F. graminearum to compare the differences of FgV1-SD4 infection on fungal morphology and pathogenicity. The comparative approach based on the ORF2 sequence alignments to the other known strains narrowed down the determinant of hypovirulence to two amino residues and 3’UTR folding.