A nine-year genetic survey of the causal agent of Dutch elm disease, Ophiostoma novo-ulmi in Winnipeg, Canada

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

“…In the 1990s, the first DNA-based studies were completed to characterize populations of O. ulmi and O. novo-ulmi Hintz et al 1991;Bates et al 1993;Hoegger et al 1996). Later studies explained the genetic diversity of DED fungi populations, mainly in Europe and North America, and reported (i) higher diversification of DED fungi populations in Europe than in North America; (ii) coexistence of O. ulmi and O. novo-ulmi during the initial stages of the second pandemic and the presence of rare but transient hybrids between the two species in Europe (Brasier et al 1998); (iii) rapid replacement of O. ulmi by O. novo-ulmi at each location; and (iv) rapid emergence of hybrids between the two subspecies of O. novo-ulmi, the European and North American races Temple et al 2006;Solla et al 2008;Brasier and Kirk 2010). The genomes of O. ulmi and O. novo-ulmi were subsequently sequenced and annotated (Forgetta et al 2013;Khoshraftar et al 2013;Comeau et al 2015), adding to information gathered earlier using traditional molecular methods.…”

Genomics of the Dutch elm disease pathosystem: are we there yet?

“…They further indicated that RAPDs were superior to restriction fragment length polymorphisms (RFLPs), used previously (Hintz et al 1991, Bates et al 1993 for distinguishing between subspecies americana and novoulmi within O. novo-ulmi. Over the following years, additional population structure studies using PCR-derived markers were conducted in Italy (Santini et al 2005), Spain (Solla et al 2008), the Netherlands (Brasier & Kirk 2010) and Canada (Temple et al 2006). From these and other studies, it is clear that European populations of DED fungi are more diverse than North American ones.…”

“…Ophiostoma ulmi was still found in parts of Europe in the early 21 st century (Solla et al 2008), whereas this species has not been reported in North America since 1991 (Houston 1991 (Hoegger et al 1996, Brasier et al 1998, Brasier 2001, Konrad et al 2002, Santini et al 2005, Brasier & Kirk 2010, but not in North America, where O. novo-ulmi subsp. americana seems to be the sole DED taxon and is characterized by large clonal populations (Temple et al 2006). The population structure of the North American population of O. novo-ulmi is typical of that of recently-introduced pathogens experiencing a genetic bottleneck, and differs markedly from what has been reported in the closely-related species O. piceae (Gagné et al 2001), as well as in the more distant Ophiostomatoid species Grosmannia clavigera (Tsui et al 2012) which are genetically more diverse and appear to be indigenous to North America.…”

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

“…Over a nine-year period we observed no increase in the diversity of vegetative compatibility ( vc) types or nuclear genotypes and populations of the pathogen in western Canada are essentially represented by two very large clones [13]. This scenario is very different in Europe where the pathogen has very quickly established a variety of vc types behind the disease front, typically within a period of six to ten years [14].…”

“…It would therefore be anticipated that the clonal populations in western Canada would be relatively free of dsRNA viruses. In both the 1993 and 2002 sample set, we were only able to find one isolate in each group infected with dsRNA [13]. Both isolates were found in close proximity and their dsRNA profiles were identical in size and banding pattern, suggesting spread of this dsRNA has been limited.…”