Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/11/2003
Publication Date: 7/22/2003
Citation: Diaby, M., Casler, M.D. 2003. RAPD marker variation among smooth bromegrass cultivars. Crop Science. 43(4):1538-1547. Interpretive Summary: The level of genetic diversity within and among smooth bromegrass (Bromus inermis Leyss.) cultivars and land races is unknown. We quantified diversity within and among 40 smooth bromegrass cultivars and land races using 97 random amplified polymorphic DNA markers. Markers were associated with geographic origin, climatype, phenotypic classification, and selection for in vitro dry matter digestibility. Clustering based on molecular markers was broadly concordant with clustering based on agronomic and morphological traits. As with other cross-pollinated species, most genetic variability was within populations. There has been no loss of genetic diversity in the 50 years since smooth bromegrass breeding began in North America. The RAPD markers identified new sources of genetic variability that had not previously been considered due to apparent similarity in phenotype and pedigree. Smooth bromegrass breeders and germplasm curators can use this information to target germplasm for crosses, to develop germplasm pools, and to identify sources of potentially new germplasm.
Technical Abstract: The level of genetic diversity within and among smooth bromegrass (Bromus inermis Leyss.) cultivars and land races is unknown. The objective of this study was to investigate and characterize genetic diversity of smooth bromegrass cultivars and selected populations based on randomly amplified polymorphic DNA (RAPD) markers. Variation among 277 individual plants from 40 smooth bromegrass cultivars was evaluated using RAPD markers. Nineteen primers evaluated amplified 97 informative amplicons. Several RAPD marker bands showed unique patterns of mean frequency differences among germplasm groups. A dendrogram constructed from average linkage cluster analysis did not indicate any clear pattern of division based on discrete or putative climatype or adaptation zones. There was considerable correspondence to known pedigree relationships revealed from a previous smooth bromegrass morphological clustering analysis, particularly for lines that are closely related to each other. The two inter-specific hybrids between Bromus inermis and B. pumpellianus (Polar) and B. riparius (S-9183-H) did not exhibit any species-specific markers. All groups of smooth bromegrass germplasm were found to have high within-population genetic variation that ranged from 84% to 96% of the total, reflecting the outcrossing reproduction and probably the complex inheritance of smooth bromegrass. Analysis of molecular variance showed the largest inter-population genetic variation for contemporary germplasm sources, supporting morphological studies for the existence of genetic variability among contemporary smooth bromegrass germplasms. These results suggest that landrace cultivars likely remain useful for germplasm improvement and cultivar development.