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Submitted to: Euphytica
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 8/10/2001 Publication Date: N/A Citation: N/A Interpretive Summary: Alfalfa (Medicago sativa) is fourth in total acreage among crops grown in the U.S. and is a very important hay crop worldwide. As with all crops,there are problems that cannot be solved without an influx of new genes, and plant explorations are routinely mounted to make such genes available to the plant breeder. Of particular interest to the alfalfa community are genes for improving tolerance of cold stress and wet soils in cultivated alfalfa from 2 species (Medicago edgeworthii and ruthenica) from the People's Republic of China (PRC). Seeds were collected from edgeworthii and M. ruthenica and a molecular analysis was conducted on DNA from plant tissue to assess the potential for crossing with alfalfa. In this case, DNA was not extracted from the nucleus but from inclusions in the cytoplasm called mitochondria and chloroplasts, whose DNA traces back to a very early time in the evolution of plant species. The research indicated that alfalfa and the two PRC species are genetically distant but that the genetic differences do not necessarily preclude the possibility of adding the exotic PRC genes to alfalfa. The information in this report should be of considerable value to both public and private alfalfa scientists. Technical Abstract: Medicago edgeworthii Sirjaev and M. ruthenica (L.) Ledebour are allogamous, diploid (2n=2x=16) perennials with flat pods. Medicago edgeworthii is indigenous to the Himalayas and alpine areas west to Afghanistan, and Medicago ruthenica is found in Siberia, Mongolia, and Manchuria on open hillsides and mixed grass steppes. Because both species have a remarkable ability to survive extreme cold and poor soils, the possibility of hybridizing them with alfalfa (M. sativa L.) is being investigated. The objective of this research was to conduct an organelle based molecular assessment of the genetic relatedness of cultivated alfalfa (2n=4x=32) to M. edgeworthii and M. ruthenica. A hypervariable, intergenic region of cpDNA was amplified, and mtDNA was amplified with two primer pairs developed from soybean (Glycine max L.) mtDNA sequences.Cluster analyses grouped some M. edgeworthii and M. ruthenica entries with alfalfa entries and there may be sufficient genetic similarity such that interspecific hybridization could be feasible among selected clones, although the possibilities are most problematic for alfalfa x M. ruthenica crosses. |
