|Lee Marzano, Shin-yi - University Of Illinois|
|Hobbs, Houston - University Of Illinois|
|Nelson, Berlin - North Dakota State University|
|Eastburn, Darin - University Of Illinois|
Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/16/2015
Publication Date: 5/1/2015
Publication URL: http://handle.nal.usda.gov/10113/61160
Citation: Lee Marzano, S., Hobbs, H.A., Nelson, B.D., Hartman, G.L., Eastburn, D.E., McCoppin, N.K., Domier, L.L. 2015. Transfection of Sclerotinia sclerotiorum with in vitro transcripts of a naturally occurring interspecific recombinant of Sclerotinia sclerotiorum hypovirus 2 significantly reduces virulence of the fungus. Journal of Virology. 89:5060-5071.
Interpretive Summary: Sclerotinia sclerotiorum is a fungal plant pathogen that causes necrotic diseases (e.g., white mold) in more than 400 plant species, which results in yield losses in major crops each year. However, the diseases caused by S. sclerotiorum have not been adequately controlled by conventional technologies thus far. Mycoviruses have been used successfully to reduce losses caused by fungal plant pathogens. In this study we infected S. sclerotiorum with a cloned copy of the genome of Sclerotinia sclerotiorum hypovirus 2 (SsHV2) and established a cause-and-effect relationship between SsHV2 infection and reductions in the virulence of the fungus. These results provide direct evidence that hypoviruses have the potential to reduce the severity of white mold diseases and will be of interest to researchers investigating biological controls of fungal diseases and interactions between fungal plant pathogens and mycoviruses.
Technical Abstract: A recombinant strain of Sclerotinia sclerotiorum hypovirus 2 (SsHV2) was identified from a North American Sclerotinia sclerotiorum isolate (#328) from lettuce (Lactuca sativa L.) by high-throughput sequencing of total RNA. The 5’ and 3’ terminal regions of the genome were determined by rapid amplification of cDNA ends. The assembled nucleotide sequence was up to 92% identical to two recently reported SsHV2 strains, but contained a deletion near its 5’ terminus of more than 1.2 kb relative to the other SsHV2 strains and an insertion of 524 nt that was distantly related to Valsa ceratosperma hypovirus 1. This suggests that the new isolate is a heterologous recombinant of SsHV2 with a yet uncharacterized hypovirus. We named the new strain Sclerotinia sclerotiorum hypovirus 2 Lactuca (SsHV2L) and deposited the sequence in Genbank with accession number KF898354. Sclerotinia sclerotiorum isolate #328 was coinfected with a strain of Sclerotinia sclerotiorum endornavirus 1 and debilitated compared to cultures of the same isolate that had been cured of virus infection by cycloheximide treatment and hyphal tipping. To confirm that SsHV2L was the causal agent of hypovirulence, a full-length cDNA of the greater than 14 kb viral genome was cloned. Transcripts corresponding to the viral RNA were synthesized in vitro and transfected into a virus-free isolate of S. sclerotiorum, DK3. Isolate DK3 transfected with SsHV2L was hypovirulent on soybean and lettuce and exhibited delayed maturation of sclerotia relative to virus-free DK3, completing Koch’s postulates for the association of hypovirulence with SsHV2L.