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Title: RELATIONSHIPS OF WEEDY AND NATIVE THISTLES (CIRSIUM) IN THE NORTHERN GREAT PLAINS

Author
item Slotta, Tracey
item Horvath, David
item Foley, Michael

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/30/2005
Publication Date: 2/13/2006
Citation: Slotta, T.A., Horvath, D.P., Foley, M.E. 2006. Relationships of weedy and native thistles (Cirsium) in the Northern Great Plains. [Abstract]. Weed Science Society of America Abstracts 46:33.

Interpretive Summary: Poster Number 114: Relationships of weedy and native thistles (Cirsium) in the Northern Great Plains Canada (Cirsium arvense) and Bull (C. vulgare) thistle are European native species that invade rangeland, agriculture and natural areas throughout North America. Canada thistle is classified as a noxious weed in 41 states and can cause severe land use and economic losses. Previous efforts to find biological control agents (insects or fungi) had limited success. For example, insects released to feed on Canada or Bull thistle attacked several thistle species native to North America, one of which is considered endangered. The current study is looking at genetic markers to determine how closely related the introduced, weedy thistles are to the native species. Several genetic markers have been developed for Canada thistle and were tested for variation in the other thistle species. Most of these genetic markers successfully worked for the native species. There was limited overlap in the comparison of DNA sequences in the native European (Canada and Bull) and native North American (Swamp, Flodman’s and Wavy-leaf) thistles. Less genetic diversity was detected in the North American thistles than in the European species. Results of this project will be an asset in the search and development of more effective control measures for Canada thistle.

Technical Abstract: Canada (Cirsium arvense) and Bull (C. vulgare) thistle are Eurasian species that invade rangeland, agriculture and natural areas throughout North America. To assess the level of genetic diversity within and gene flow between Canada thistle and relatives in the Northern Great Plains, microsatellite markers were designed and compared to ISSRs (inter-simple sequence repeats) and sequences of the ITS and ETS nuclear ribosomal regions. A set of 17 ISSR markers were screened, six of which consistently amplified variable loci in Canada thistle populations across North America. Among Cirsium species sampled, Bull thistle had the greatest homology to Canada thistle ISSR loci. From 31 microsatellite loci identified in Canada thistle, eight consistently amplified variable alleles. These eight microsatellites were also surveyed among North American endemic thistles. As with the ISSR markers, Bull thistle had the greatest homology among microsatellite alleles. Alleles homologous within Cirsium were sequenced and surveyed for utility as phylogenetic tools in assessing relationship between the closely related species. Several microsatellite sequence regions were conserved between Eurasian and North American thistles. With ITS and ETS sequences, several regions differentiated between Eurasian and North American species. Analyses of all regions concurred that introduced invasive thistles and native thistles do not hybridize, even when they co-occur.