Abstract
A novel mycovirus named Fusarium oxysporum f. sp. dianthi hypovirus 2 (FodHV2) has been identified infecting isolates Fod 408 and Fod 409 of Fusarium oxysporum f. sp. dianthi from Morocco. The genome of FodHV2 is 9,444 nucleotides long excluding the poly(A) tail, and has a single open reading frame encoding a polyprotein. The polyprotein contains three highly conserved domains of UDP glucose/sterol glucosyltransferase, RNA-dependent RNA polymerase, and viral RNA helicase. In addition, particular residues of Cys, Hys, and Gly detected in the N-terminal region suggest the presence of the catalytic site of a highly diverged papain-like protease. Genomic organization, presence of particular conserved motifs, and phylogenetic analyses based on multiple alignments clearly grouped FodHV2 with the members of the family Hypoviridae. FodHV2 was transferred by hyphal anastomosis to a recipient HygR-tagged virus-free strain. The comparison of the infected and non-infected isogenic strains showed that FodHV2 did not alter the vegetative growth, neither the conidiation nor the virulence of its fungal host. Efficiency of FodHV2 transmission through the conidia was 100% in both the original and the recipient infected-isolates. To the best of our knowledge, this is the first report of a hypovirus infecting the plant pathogen F. oxysporum, and also the first one of a hypovirus detected in a fungal strain from the African continent.
Highlights
The soilborne fungal species Fusarium oxysporum contains a diversity of host–plant specific forms that cause vascular diseases in a large number of economically important crops
The most studied case is that of Cryphonectria hypovirus 1 (CHV1), a mycovirus in the family Hypoviridae that has been successfully used for the control of chestnut blight caused by Cryphonectria parasitica in Europe (Milgroom and Cortesi, 2004; Nuss, 2005)
In this work we describe and biologically characterize a putative novel virus in the family Hypoviridae, for which we proposed the name Fusarium oxysporum f. sp. dianthi hypovirus 2 (FodHV2)
Summary
The soilborne fungal species Fusarium oxysporum contains a diversity of host–plant specific forms (formae speciales) that cause vascular diseases in a large number of economically important crops. First Hypovirus in Fusarium oxysporum the use of methyl bromide, together with the difficulty in obtaining carnation varieties resistant to the different pathogenic variants (races) of the fungus, made control of this disease ineffective. The use of hypovirulence-associated mycoviruses has been proposed as a new strategy for biological control (virocontrol) of fungal diseases (Chiba et al, 2009; Ghabrial and Suzuki, 2009). The most studied case is that of Cryphonectria hypovirus 1 (CHV1), a mycovirus in the family Hypoviridae that has been successfully used for the control of chestnut blight caused by Cryphonectria parasitica in Europe (Milgroom and Cortesi, 2004; Nuss, 2005). Success in using CHV1 for the biological control of chetnust blight has prompted interest in identifying new members of this family in other phytopathogenic species. All the above-mentioned viruses have not yet been approved by the International Committee of Taxonomy for Viruses (ICTV) as members of the family Hypoviridae (Suzuki et al, 2018)
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