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Title: Assessment of Genetic Diversity Among Nondormant and Semi-Dormant Alfalfa Populations using Sequence Related Amplified Polymorphisms (SRAPs)

item Ariss, Jennifer
item Vandemark, George

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/2/2007
Publication Date: 11/1/2007
Citation: Ariss, J.J. and G.J. Vandemark.2007 Assessment of genetic diversity among nondormant and semi dormant alfalfa populations using sequence related amplified polymorphisms. Crop Science 47:2274-2284.

Interpretive Summary: Alfalfa is the most important forage crop in the US. Due to alfalfa’s widespread cultivation, a range of cultivars is available to maximize yield and survival in diverse environments and agronomic regimes. Semi-dormant and nondormant alfalfas are primarily used in regions where long-growing seasons facilitate increased yield by virtue of more annual harvests. In the past, little attention has been paid to the relationship of the semi- and nondormant alfalfa’s to each other and the historical sources of alfalfa populations. In order to assess genetic relatedness among semi-dormant and nondormant alfalfa populations, bulked DNA samples were generated from 38 alfalfa populations and subjected to genetic marker analysis using sequence related amplified polymorphisms (SRAPs). The populations selected for this investigation included 29 commercial cultivars and nine populations representing the original plant introductions of alfalfa into the US. From the 189 bulked DNA samples, 188 SRAP markers were generated that, when subjected to statistical analysis, generally grouped bulks of the same population together. Estimates of genetic similarity within and between populations were quite high yet, the SRAP markers successfully distinguished between alfalfa populations while not compromising the estimates of similarity between bulks of the same populations. Additionally, the semi-dormant populations and the nondormant populations clustered into separate groups. The results of this study suggest that using SRAP markers generated from bulked DNA samples can be useful in the general classification of existing and new alfalfa populations.

Technical Abstract: Synthetic alfalfa populations consist of genetically heterogeneous plants, which has contributed to difficulties in applying molecular markers for examining genetic relationships among alfalfa cultivars. Molecular marker techniques combined with bulked plant DNA analyses provide perhaps the best combination of accuracy and high throughput for alfalfa population characterization and differentiation. A study was conducted to assess how sequence-related amplified polymorphisms (SRAPs) would estimate genetic similarity among 29 nondormant and semi-dormant alfalfa populations representing diverse breeding sources and the nine historically recognized US germplasm sources using 20-plant bulked DNA templates. Genetic similarity (Gs) estimates ranged from 0.79 to 0.92 for bulks within a population and from 0.61 to 0.91 for bulks between populations. Cluster analysis based on Gs showed separation of fall dormancy classes 6, 7 and 8 from fall dormancy classes 9, 10, and 11 and in many examples, DNA bulks of the same cultivars clustered together. Cultivars tended to fall into two groups corresponding to broad fall dormancy categories, semi-dormant or nondormant, which may be useful for classifying relative dormancies of plant introductions and new cultivars. This study demonstrates that the amplification of SRAP markers from DNA extracted from bulked plant samples is an efficient method for estimating genetic similarity both within and between a large numbers of populations.