Two novel mitoviruses from a Canadian isolate of the Dutch elm pathogen Ophiostoma novo-ulmi (93–1224)

Abstract

BackgroundOphiostoma novo-ulmi is the causative agent of Dutch elm disease (DED). It is an ascomycetous filamentous fungus that ranks as the third most devastating fungal pathogen in Canada. The disease front has spread eastward and westward from the epicentre in Ontario and Quebec and is threatening elm populations across the country. Numerous mitigation strategies have been tried to eradicate this pathogen, but success has thus far been limited. An alternative approach might utilize double-stranded RNA (dsRNA) mycoviruses which have been reported to induce hypovirulence in other fungi.MethodsUsing a modified single primer amplification technique (SPAT) in combination with chromosomal walking, we have determined the genome sequence of two RdRp encoding dsRNA viruses from an O. novo-ulmi isolate (93–1224) collected from the disease front in Winnipeg.ResultsWe propose that these viruses, which we have named OnuMV1c and OnuMV7 based on sequence similarity to other Ophiostoma mitoviruses, are two new members of the genus Mitovirus in the family Narnaviridae.ConclusionsThe discovery of such dsRNA elements raises the potential for engineering these viruses to include other genetic elements, such as anti-sense or interfering RNAs, to create novel and highly specific biological controls. Naïve fungal hosts could be infected with both the engineered molecule and a helper mitovirus encoding an RdRp which would provide replication capacity for both molecules.

Breeding and scientific advances in the fight against Dutch elm disease: Will they allow the use of elms in forest restoration?

“…The method with greatest potential for large-scale application appears to be the use of mycoviruses called d-factors (Brasier 2000b). Several mycoviruses have been identified as highly host specific colonizers of O. novo-ulmi Hintz et al 2013). Many of them can severely reduce mycelial growth and sporulation of the pathogen, including reduced viability of the conidia and perithecial production (Brasier 1986).…”

Full genome sequence of a putative novel mitovirus isolated from Rhizoctonia cerealis

“…For example, OMV1a, OMV3a, OMV5 and OMV6 are from O. novo-ulmi but they are distributed discontinuously in the phylogenetic tree [5]. The OMV3a from O. novo-ulmi is conspecific with Sclerotinia homoeocarpa mitovirus (ShMV) from S. homoeocarpa, and OMV3b is conspecific with Botrytis cinerea mitovirus 1 (BcMV1) from B. cinerea [5,15]. This suggests that the origins and evolutionary relationships of mitoviruses are complex.…”

“…No gene has been identified thus far that encodes a capsid protein. Like several other RNA viruses of lower eukaryotes, mitoviruses are confined within lipid vesicles [5]. The unique …”

Evolving symbioses between insects and fungi that kill trees in Canada: new threats associated with invasive organisms

“…The American elm, Ulmus americana Linnaeus, which is widely planted in urban environments, has been particularly affected by the disease, and major Canadian cities such as Toronto, Ontario have lost a significant percentage of their elms (Hubbes 1999). Management of Dutch elm disease has been a priority for cities such as Winnipeg, Manitoba, which lost more than 21 000 trees between 2009 and 2013 (Hintz et al 2013); the province of Saskatchewan has invoked regulations to prevent spread of the disease (Anonymous 2005); however, the disease is present in Saskatchewan and it threatens Alberta (Hubbes 1999).…”

“…Although it is very unfortunate that Dutch elm disease was introduced into Canada, there have been two distinct benefits associated with its introduction: First, as a high priority pathogen, several important research programmes were launched in Canada to investigate topics such as population genetics of invasive pathogens (i.e., Hintz et al 1993;Temple et al 2006), pathogen gene expression and infection processes (i.e., Temple et al 1997;Et-Touil et al 2005), and alternative pathogen management strategies (i.e., Hubbes 1999; Temple et al 2006;Hintz et al 2013). Second, public awareness of the impacts of invasive alien species has been raised through the outreach activities of non-governmental agencies such as the Society to Prevent Dutch Elm Disease in Alberta, which promotes healthy urban forests.…”