Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/10/2007
Publication Date: 11/7/2007
Citation: Casler, M.D., Vogel, K.P., Taliaferro, C.M., Ehlke, N.J., Berdhal, J.D., Brummer, E.C., Kallenbach, R.I., West, C.P. 2007. Latitudinal and longitudinal adaptation of switchgrass populations. Crop Science. 47:2249-2260. Interpretive Summary: Switchgrass (Panicum virgatum L.) is an important warm-season native grass, used for livestock feed and biofeedstock production, soil and wildlife conservation, and prairie restoration in a large portion of the USA. Varieties and ecotypes of switchgrass for agronomic use are currently marketed across broad regions, with little concern for their region of adaptation. Conversely, ecotypes used for conservation and restoration are highly restricted in their movement, with regulations often stating that ecotypes can be moved no more than 100 miles. Our data and results indicate that north-south movement of varieties and ecotypes is critical, due to changes in temperature and daylength, and that varieties for biomass production could be moved one hardiness zone north or south of their origin, but ecotypes for conservation or restoration could be restricted to their hardiness zone of origin. Both varieties and ecotypes could easily tolerate greater east-west movement, across fairly broad ecoregions, such as the historical eastern forest ecoregion or the historical tallgrass prairie. These results will be of value to prairie conservationists and restorationists, extension agronomists, and farmers interested in growing switchgrass for either livestock or biomass production.
Technical Abstract: Switchgrass (Panicum virgatum L.) is an important warm-season native grass, used for livestock feed and biofeedstock production, soil and wildlife conservation, and prairie restoration in a large portion of the USA. The objective of this research was to quantify the relative importance of latitude and longitude in regulating the adaptation and agronomic performance of a diverse group of switchgrass populations. Six populations were chosen to represent remnant prairie populations on two north-south transects, one in the Great-Plains ecoregion and one in the historical Eastern-Forest ecoregion. The six populations were evaluated for agronomic traits at 12 locations ranging from 36 to 47ºN latitude and 88 to 101ºW longitude. Although the population x location interactions accounted for only 10 to 31% of the variance among population means, many significant changes in ranking and adaptive responses were observed. A larger adaptive response was observed for ground cover 40 months after planting, with higher ground cover for northern-origin populations in hardiness zones 3 and 4 and higher ground cover for southern-origin populations in hardiness zones 5 and 6. There were no adaptive responses related to longitude (ecoregion), which included precipitation and numerous soil factors. Hardiness zones, related to latitude and temperature provide boundaries and guidelines for optimal recommendation, distribution, and use of switchgrass germplasm. Prairie-remnant populations for use in conservation and restoration and agronomic populations for use in biomass production should not be moved more than one hardiness zone from their origin, but some can be moved east or west outside of their original ecoregion, depending on results from field tests.