Novel mycoviruses discovered from metatranscriptomics survey of soybean phyllosphere phytobiomes

Authors: MARZANO, SHIN-YI - University Of Illinois; Domier, Leslie

Submitted to: Virus Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2015
Publication Date: 2/2/2016
Citation: Marzano, S.L., Domier, L.L. 2016. Novel mycoviruses discovered from metatranscriptomics survey of soybean phyllosphere phytobiomes. Virus Research. 213(2):332-342.

Interpretive Summary: Soybean provides essential nutrients for both humans and food animals, and is also an important source of bioenergy. Each year, fungal diseases significantly reduce soybean yields and seed quality. Some viruses that infect plant pathogenic fungi can be beneficial to plants in that they reduce the ability of the fungi to cause disease. Most studies of beneficial fungal viruses have been conducted using fungi that can be grown on culture media in the lab. However, the fungi that cause some of the most devastating plant diseases cannot be grown on culture media. To identify viruses infecting fungi associated with soybean plants in the field, leaf samples were collected in 2008 and 2009 from over 3,000 soybean plants in Illinois and assayed by high-throughput sequencing for the presence of viruses that were similar to previously described fungal viruses. The analyses identified portions of the genomes of 22 fungal viruses with similarity to 10 distinct viral lineages. Only one of the viruses had been described previously. The viruses identified in this study add to the biological diversity of fungal viruses associated with plants and will be useful to scientists interested in identifying biological agents that can moderate fungal diseases.

Technical Abstract: Mycoviruses can be beneficial to plants in that they can debilitate pathogenic fungi thereby reducing the severity of associated plant diseases. Studies to date have focused primarily on culturable fungi that represent a fraction of natural fungal populations. The nonculturable fungi, however, can harbor diverse populations of mycoviruses that reduce plant disease or enhance resistance to abiotic stress. Metatranscriptome analysis of field-grown plant samples using high-throughput sequencing offers the possibility of unbiased detection and quantification of mycoviruses regardless of the culturability of their fungal hosts together with the complete associated microbial consortia. In this study, we describe the fungal viromes of the phyllosphere of production soybean fields in Illinois, USA by analyzing the metatranscriptomes of thousands of soybean leaf samples collected during the 2008 and 2009 growing seasons. The analyses identified 25 partial genome sequences of 22 mycoviruses, only one of which had been described previously. The novel mycovirus genomes showed similarity to 10 distinct lineages including the genera Botybirnavirus, Endornavirus, Mitovirus, Mycoflexivirus, Ourmiavirus, Partitivirus, Totivirus, Victorivirus, family Tombusviridae, order Mononegavirales, and the recently proposed genus Gemycircularvirus. The present study adds to the wealth of mycoviruses associated with plant phytobiomes and establishes groundwork needed for further characterization of the viruses.