Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2005
Publication Date: 7/7/2005
Citation: Sim, S.C., Chang, T., Curley, J., Warnke, S.E., Barker, R.E., Jung, G. 2005. RFLP marker based analysis of large-scale chromosomal rearrangements differentiating the Lolium genome from other Poaceae species. Theor. Appl. Genet. 110:1011-1019.
Interpretive Summary: DNA fragments that have been used to locate genes in wheat, barley, oats and rice were used to map the chromosomes of ryegrass. The use of a common set of DNA fragments to create maps in all of these species allows the level of rearrangement since the species diverge to be established. The chromosome rearrangements that were identified indicate that ryegrass has a gene order that is very similar to wheat and oats and less similar to rice. However, large segments of ryegrass chromosomes show a gene order that is very similar to these other important grass species. This conservation of gene order may speed up efforts to identify important genes in ryegrass by using information from more extensively studied grass species.
Technical Abstract: An RFLP-based genetic map of ryegrass (Lolium) was constructed for comparative mapping with other Poaceae species using heterologous anchor probes. The genetic map contained 120 RFLP markers from cDNA clones of barley (Hordeum vulgare L.), oat (Avena sativa L.), and rice (Oryza sativa L.), covering 786 cM on 7 linkage groups (LGs). RFLP marker based genome comparison of ryegrass with the Triticeae, oat, and rice genomes revealed new evidence of unique large-scale chromosomal rearrangements differentiating the ryegrass genome from other Poaceae species. Ryegrass LGs showed two chromosomal rearrangements differentiating ryegrass from the Triticeae, four from oat, and five from rice. Evidence of two basic evolutionary rearrangements (rice 5-10-5 and rice 6-8-6) that differentiate the Pooideae from the other subfamily species of the Poaceae, were observed in ryegrass LGs1 and 7, respectively. Furthermore, we observed a similar pattern of chromosomal rearrangements between ryegrass LGs4, 5, and 6 and oat chromosomes E, F, and G relative to the Triticeae chromosomes 4 and 5. Based on this we support the close taxonomic relationship of ryegrass and oat, despite a higher number of gross structural rearrangements detected relative to oat than to the Triticeae. Our results clearly suggested that the ryegrass genome is more closely related to oat and the Triticeae than to rice.