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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVED PLANT GENETIC RESOURCES FOR PASTURES AND RANGELANDS IN THE TEMPERATE SEMIARID REGIONS OF THE WESTERN U.S.

Location: Forage and Range Research

Title: Wide-scale population sampling identifies three phylogeographic races of Leymus cinereus and low-level genetic admixture with Leymus triticoides

Authors
item Culumber, C -
item Larson, Steven
item Jones, Thomas
item Jensen, Kevin

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 11, 2013
Publication Date: May 10, 2013
Citation: Culumber, C.M., Larson, S.R., Jones, T.A., Jensen, K.B. 2013. Wide-scale population sampling identifies three phylogeographic races of Leymus cinereus and low-level genetic admixture with Leymus triticoides. Crop Sci. 53:996-1007.

Interpretive Summary: Basin wildrye and creeping wildrye are cross-pollinating perennial grasses native to western North America. These divergent species are generally adapted to different habitats, but are often found together and have potential to form fertile hybrids. Cultivars of both species are used in agriculture and conservation. However, patterns of genetic structure and gene flow have not been tested. Thus, multi-locus DNA fingerprinting and chloroplast DNA sequences were evaluated from 536 L. cinereus and 43 L. triticoides plants from 224 locations of western United States and Canada. Bayesian-cluster analysis detected possible admixture between species, but only 2.2% of the plants showed more than 10% introgression. However, three L. cinereus races corresponding to the Columbia, Rocky Mountain, and Great Basin regions were distinguishable. Approximately 91% and 73% of the Columbia and Great Basin accessions were octoploid (contain eight chromosome sets), respectively, where 82% of the Rocky Mountain accessions were tetraploid (containing four chromosome sets). Approximately 35.9% and 7.1% of the multi-locus DNA fingerprinting variation was apportioned among species and races, respectively. Conversely, 8.0% and 11.0% of the chloroplast DNA sequence variation was apportioned among species and races. Correlation between genetic and geographic distances among collection sites was detectable within L. cinereus, but diminished within races.

Technical Abstract: Basin wildrye (Leymus cineneus) and creeping wildrye (L. triticoides) are out-crossing perennial grasses native to western North America. These divergent species are generally adapted to different habitats, but are often found together and have potential to form fertile hybrids. Cultivars of both species are used in agriculture and conservation. However, patterns of genetic structure and gene flow have not been tested. Thus, multi-locus AFLP genotypes and chloroplast DNA sequences were evaluated from 536 L. cinereus and 43 L. triticoides plants from 224 locations of western United States and Canada. Bayesian-cluster analysis detected possible admixture between species, but only 2.2% of the plants showed more than 10% introgression. However, three L. cinereus races corresponding to the Columbia, Rocky Mountain, and Great Basin regions were distinguishable. Approximately 91% and 732% of the Columbia and Great Basin accessions were octoploid, respectively, whereas 82% of the Rocky Mountain accessions were tetraploid. Approximately, 35.9% and 7.1% of the AFLP variation was apportioned among species and races, respectively. Conversely 8.0% and 11.0% of the chloroplast DNA sequence variation was apportioned among species and races. Linkage disequilibrium between AFLP markers and correlation between genetic and geographic distances were detectable within L. cinereus, but diminished within races.

Last Modified: 4/21/2014