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Submitted to: Crop Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/30/2003 Publication Date: 6/1/2004 Citation: Casler, M.D. Variation among and within smooth bromegrass collections from rural cemetaries. Crop Science. 2004. v.44. p.978-987. Interpretive Summary: Smooth bromegrass is poorly adapted to management-intensive rotational grazing because of slow and limited regrowth potential. In an effort to find existing germplasm with tolerance to frequent cutting, I collected and evaluated smooth bromegrass germplasm from fence and sod habitats of 30 rural cemetaries in Iowa, Minnesota, and Wisconsin. For most cemetaries, fence and sod populations probably originated from one source of germplasm. Natural selection over many decades, mostly in the sod habitat, has caused fence and sod populations to diverge. Sod populations appear to have developed a lower growing habit and slower growth rate, limiting their forage productivity under both infrequent and frequent harvesting managements. Smooth bromegrass plants from rural cemetary sods may have some value for cultivar development, but do not represent a silver bullet for developing a grazing type of smooth bromegrass in the near future. This research provides information on gene migration, natural selection, and natural variation for other scientists and researchers with interests in forage and range natural resources. Technical Abstract: Smooth bromegrass (Bromus inermis Leyss) is poorly adapted to management-intensive rotational grazing because of slow and limited regrowth potential. In an effort to find existing germplasm with tolerance to frequent cutting, smooth bromegrass germplasm was collected from fence and sod habitats of 30 rural cemetaries in Iowa, Minnesota, and Wisconsin. Ramets of 25 clones from each habitat of each cemetary were transplanted into a replicated and randomized experiment at Arlington, WI and evaluated from 1999 to 2002. Within-population genotypic variance was greater in sod populations for plant height and diameter. Across cemetaries, genotypic variances for regrowth vigor of sod and fence populations were positively correlated. These two results suggest that a large amount of genotypic variability is being maintained at some cemetaries by migration into sod populations and disruptive selection favoring different genotypes in the two habitats. Fence populations averaged 7.6% higher in reproductive forage yield, 9.5% higher in vegetative forage yield, 6.0% taller, 8.4% wider plant diameter, 4.7% higher regrowth vigor, and 6.9% higher frequent-harvest forage yield than sod populations. Sod populations tended to be more variable among cemetaries than fence populations, suggesting greater adaptive responses to selection pressure. Two sod populations were highly unusual, one with unusually fast regrowth arising from tillers that initiated growth almost instantly after apical dominance was removed, the other with extremely high reproductive forage yield, but low regrowth vigor. This germplasm may have value in the development of smooth bromegrass germplasm with improved tolerance to frequent cutting or grazing. |
