Graduate Thesis Or Dissertation
 

Hybridization between yellow starthistle (Centaurea solstitialis) and meadow knapweed (Centaurea x moncktonii)

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/3n204281x

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  • Centaurea solstitialis L. (yellow starthistle) and C. × moncktonii Britt. (meadow knapweed) are members of the genus Centaurea in the Asteraceae family. Both species have become serious management concerns as invasive species in North America, often displacing native vegetation and costing land managers millions of dollars to eradicate. Seven plants were found in southwestern Oregon that appear to be hybrids between C. solstitialis and C. × moncktonii. These plants were identified as hybrids based on bract shape, flower color, and the presence of the putative parent species at the same sites. Hybridization between these two species may present potential management problems, such as the hybrids developing into a viable species or gene flow between the parent species. Meadow knapweed originated through hybridization and colonized a larger range than either of its parent species. If hybrids produce viable pollen or fertile seed, backcrossing with one of the parent species could transfer alleles from one parent species to the other. Hybrids have the potential to transgress parent species for some traits and show increased fitness relative to the parent species. The putative C. solstitialis × C. moncktonii hybrids were identified based primarily on intermediate morphological traits. To test the hypothesis that these species can produce hybrids, controlled crosses between yellow starthistle and meadow knapweed were attempted. These crosses produced thirty hybrids that fit the morphological description used by Roché and Susanna (2010) to identify plants as C. solstitialis × C. moncktonii hybrids. The hybrids generated from the controlled crosses germinated from seeds that came from yellow starthistle plants. Genome size, measured using flow cytometry, and four quantifiable morphological characters were measured on the putative hybrids, hybrids generated through controlled crossing, and the parent species. When the group means were compared, there was no significant difference between the putative hybrids and the hybrids generated through controlled crossing for any of the characters. Both putative and artificial hybrids were backcrossed with the parent species to determine the likelihood of backcrossing. Backcrossing did occur, with the hybrids serving as both maternal parent and pollen parent at very low rates (<1%). Management of the hybrid should focus on prevention of pollination in order to prevent introgression between the parent species.
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