novo ulmi sampled across Saskatche wan and Manitoba were analyzed making use of both nuclear and mitochondrial genetic markers and only restricted genetic variability was detected. All of the isolates repre sented the aggressive sub group and incorporated only two distinct nuclear and 4 mitochondrial genotypes, The vast majority of isolates had been of a single genotype, suggesting that one genetic person dominated the sample spot. Later analysis in the same area in contrast isolates collected in 1993 and 2002, using each RAPD markers and an evaluation of vegetative compatibility, It had been hypothesized that new vc sorts would produce swiftly soon after the condition front had passed through the region, Compatibility exams confirmed a single vc group, demonstrating that a genetically uni kind population persists in western Canada.
In contrast, a substantially better diversity of vc styles has become documen ted in the Eurasian aggressive this article race of O. novo ulmi, as compared to populations in the North Ameri can aggressive race, the EAN and NAN sub populations of O. novo ulmi have considering the fact that been re designated as subspecies novo ulmi and americana, respectively, A very low diversity of vc types for your amer icana subspecies appears for being concentrated during the southern Good Lakes, that’s consistent with its preliminary detection in this area.
places colonized additional just lately, which include western Canada, display extremely restricted vc diver sity, In parts of Europe encountering a well estab lished epidemic of subspecies novo ulmi that was initially characterized by a uniformity of vc sorts, vege tative incompatibilities are already reported inside 6 to ten years, In read the article contrast, the comparatively lower diversity of vc groups observed to the subspecies americana is atypical of an established pathogen epidemic, though swiftly expanding pathogen populations have previously been reported to exhibit lower genetic diversity, Variables influencing the growth of vc groups and greater genetic diversity in subspecies novo ulmi ought to thus be considerably different from individuals encoun tered by subspecies americana. There is no clear expla nation for your restricted genetic variability observed within the O. novo ulmi subspecies americana population in wes tern Canada.
The report of only two nuclear genotypes, and no transitional genotypes, suggests that sexual occasions are rare and that its propagation continues to be predo minantly by asexual usually means inside the timeframe of this epidemic, Inside a former review of North America populations of this species, two feasible variables contri buting to low vc diversity were suggested. the infrequent occurrence of deleterious d aspect viruses in populations give a lower level of selection for new vc varieties along with the frequent predominance of single vc clones on a host substrate doesn’t favour the establishment of novel vc sorts, The role of host genetic diversity has not been evaluated to any extent in studies of Dutch elm disease and it need to be mentioned that surveys of elm populations in western Canada are actually carried out generally in urban environments and may well as a result have favoured planted nursery stocks of this species.