Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/28/2008
Publication Date: 7/15/2008
Citation: Bhattarai, K., Johnson, D.A., Jones, T.A., Gardner, D.R., Connors, K.J. 2008. Physiological and Morphological Characteristics Among Ecotypes of Basalt Milkvetch (Astragalus Filipes): Basis for Plant Improvement. Rangeland Ecology and Management 61: 444-455. Interpretive Summary: Arid and semi-arid rangelands are usually limited in nitrogen. However, only a few native legumes are available for revegetation of semi-arid rangelands in the western U.S. Basalt milkvetch (Astragalus filipes) is a native legume that is widely distributed in western North America and holds promise for rangeland revegetation. In an effort to identify promising ecotypes of basalt milkvetch, we collected seed at 67 various locations in Utah, Nevada, Idaho, Oregon, California, and Washington. We transplanted seedlings of these 67 collections at two sites in northern Utah and evaluated mature plants for various physiological and morphological characteristics. Results from our research showed that basalt milkvetch is not toxic to livestock and wildlife and produces high quality forage. Results from our studies provide important data for identifying basalt milkvetch collections that have the greatest potential for revegetation of degraded rangelands.
Technical Abstract: Astragalus filipes Torr. ex A. Gray (basalt milkvetch or threadstalk milkvetch) is a legume that is widely distributed in western North America and holds promise for revegetation and restoration programs in the western U.S.A. Seed of 67 accessions was collected in 2003 from Utah, Nevada, Idaho, Oregon, California, and Washington. Field-collected forage samples from these accessions had non-detectable or low levels of selenium, swainsonine, and nitrotoxins. Accessions were evaluated at Providence and Millville in northern Utah in 2005 and 2006. At Providence, accessions from north-central Oregon exhibited high biomass yield in summer and fall during both years. Basalt milkvetch accessions with low biomass generally had high crude protein concentration. Acid-detergent fiber (ADF) and neutral-detergent fiber (NDF) were positively correlated with biomass yield. At Millville, accessions from north-central Oregon exhibited high biomass and seed yield. Seed weight per 100 seeds varied among basalt milkvetch accessions in both years at Millville. Plants at Millville treated with imadicloprid insecticide had greater seed yields in 2006, but not in 2005. When averaged across sites and years, a high correlation between number of stems and biomass (r=0.82, P<0.0001) indicated that number of stems is a reliable predictor of high biomass and seed yield. Principal component analysis of 7 consolidated plant traits identified 2 principal components that accounted for 60 and 15% of the variation among accessions. The first principal component was negatively correlated with elevation (r=-0.71, P<0.01) and positively correlated with latitude (r=0.46, P<0.01). The second principal component was positively correlated with elevation (r=0.36, P<0.01) and negatively correlated with latitude (r=-0.47, P<0.01). These results are beneficial in identifying basalt milkvetch accessions that hold promise for plant improvement efforts.