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Title: Suppressing infection cushion formation by two novel hypovirulence-associated mycoviruses in the phytopathogenic fungus Botrytis cinerea

item HAO, FANGMIN - Huazhong Agricultural University
item DING, TING - Huazhong Agricultural University
item WU, MINGDE - Huazhong Agricultural University
item ZHANG, JING - Huazhong Agricultural University
item YANG, LONG - Huazhong Agricultural University
item Chen, Weidong
item LI, QUOQING - Huazhong Agricultural University

Submitted to: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2018
Publication Date: 5/13/2018
Citation: Hao, F., Ding, T., Wu, M., Zhang, J., Yang, L., Chen, W., Li, Q. 2018. Suppressing infection cushion formation by two novel hypovirulence-associated mycoviruses in the phytopathogenic fungus Botrytis cinerea. Viruses. 10:254.

Interpretive Summary: The plant pathogen Botrytis cinerea is a fungus that has a very broad host range including many economically important crops. Management of diseases caused by Botrytis mainly depends on applications of fungicides. However, Botrytis is prone to develop fungicide resistance, greatly increasing the difficulty of its control. The present study examined two mycoviruses of Botrytis. Mycoviruses are viruses of fungi that have been shown to reduce the ability of fungi to cause plant diseases. Data generated in this study indicated that the suppression of infection structure formation is responsible for the reduced disease severity caused by virus infected Botrytis. These results provide a new avenue for studying biological control of plant diseases using mycoviruses.

Technical Abstract: Botrytis cinerea is a necrotrophic fungus causing disease on many important agricultural crops. Two novel mycoviruses, namely Botrytis cinerea hypovirus 1 (BcHV1) and Botrytis cinerea fusarivirus 1 (BcFV1), were fully sequenced. The genome of BcHV1 is 10214 nt long excluding a poly-A tail and possesses one large open reading frame (ORF) encoding a polyprotein possessing several conserved domains including RNA-dependent RNA polymerase (RdRp), showing homology to hypovirus-encoded polyproteins. Phylogenetic analysis indicated that BcHV1 may belong to the proposed genus Betahypovirus in the viral family Hypoviridae. The genome of BcFV1 is 8411 nt in length excluding the poly A tail and theoretically processes two major ORFs, namely ORF1 and ORF2. The larger ORF1 encoded polypeptide contains protein domains of an RdRp and a viral helicase, whereas the function of smaller ORF2 remains unknown. The BcFV1 was phylogenetically clustered with other fusariviruses forming an independent branch, indicating BcFV1 was a member in Fusariviridae. Both BcHV1 and BcFV1 were capable of being transmitted horizontally through hyphal anastomosis. Infection by BcHV1 alone caused attenuated virulence without affecting mycelial growth, significantly inhibited infection cushion (IC) formation, and altered expression of several IC-formation-associated genes. However, wound inoculation could fully rescue the virulence phenotype of the BcHV1 infected isolate. These results indicate the BcHV1-associated hypovirulence is caused by the viral influence on IC-formation-associated pathways.