Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/5/2006
Publication Date: 11/10/2006
Citation: Vandemark, G. J., J. J. Ariss, G. A. Bauchan, R. C. Larsen, and T. J. Hughes. 2006. Estimating genetic relationships among historical sources of alfalfa germplasm and selected cultivars with Sequence Related Amplified Polymorphisms. Euphytica 152:9-16.
Interpretive Summary: Alfalfa is the fourth most important crop in American agriculture in terms of both farm gate value and acres under cultivation. Alfalfa is successfully cultivated throughout most of the country, under very different management and environmental conditions, ranging from intensively irrigated alfalfa in the southwest, to dryland cultivation in the northern great plains. A large number of commercial varieties have had to be developed to accommodate specific growing conditions throughout the country. All commercial varieties are derived from nine original populations that originated in different parts of the world. Plant breeders have had to estimate the percentage of each of these nine populations present in their improved varieties for the varieties to be commercially certified. It is very difficult to estimate these percentages in alfalfa based on pedigree records because seed is produced using bees as pollinators. We developed DNA markers for examining genetic relationships among the nine original alfalfa populations and several commercial varieties. Relationships determined using DNA markers generally agreed with previous estimations of relationships based on pedigrees and comparisons of fall dormancy. The DNA markers suggest that the commercial varieties are genetically quite distinct from the nine original source populations of alfalfa. This report demonstrates that an inexpensive molecular marker system can be used to accurately detect genetic variation in alfalfa populations. It should be possible to use these DNA markers to rapidly and accurately screen alfalfa for desired traits, which will make it easier to develop improved varieties that will ensure continued successful cultivation of this important forage crop.
Technical Abstract: Fifteen alfalfa populations, consisting of six public cultivars and nine historically recognized sources of alfalfa germplasm in North American cultivars were examined using sequence related amplified polymorphisms (SRAPs). Three bulk DNA samples from each population were evaluated with fourteen different SRAP primer pairs. This resulted in 249 different amplicons, of which over 90% were polymorphic. A dendrogram from the analysis suggests that the public cultivars are quite diverse from all the historical sources of germplasm except for M. falcata. The highest mean genetic diversity among the nine original sources of Medicago germplasm was 0.85 between PI 536535 (Peruvian) and 536536 (Indian), while the lowest (0.47) was between PI 560333 (M. falcata) and 536539 (African). The highest mean genetic similarity among the nine original sources of Medicago germplasm and the public alfalfa cultivars was 0.78 between PI 536532 (Ladak) and Vernal, while the lowest (0.59) was between PI 536539 (African) and Oneida. Relationships based on SRAP analysis appear to generally concur with expected relationships based on pedigree histories and selected traits such as fall dormancy. This report demonstrates that SRAPs are a rapid, informative, and inexpensive molecular marker system for discerning alfalfa germplasm.