Submitted to: Genome
Publication Type: Peer reviewed journal
Publication Acceptance Date: 4/1/2005
Publication Date: 8/5/2005
Citation: Mian, R.M., Saha, M.C., Hopkins, A.A., Wang, Z. 2005. Use of tall fescue EST-SSR markers in phylogenetic analysis of cool-season forage grasses. Genome. 48:637-647. Interpretive Summary: Microsatellites or simple sequence repeats (SSRs) are the DNA markers of choice for plant breeders for crop improvement. Cool season forage grasses (e.g., fescues and ryegrasses) play important roles in U.S. Agriculture. Yet for most of these forage grass species, currently there are little or no SSR markers available. The objectives were to examine the amplification of tall fescue SSR markers in 12 grass species representing eight genera of four tribes from two sub-families of Poaceae and test the applicability of these markers in a number of cool season forage grass species. More than 70 SSR primer pairs were identified that have broad usefulness in a number of important cool season forage grasses, including fescues, ryegrasses, orchardgrass, tall wheatgrass, smooth bromegrass, and Russian wildrye. These DNA markers were also useful for determination of genetic relationships among forage grasses and major crop species like rice and wheat. This study provides the forage grass scientist and breeders with a new set of DNA markers that they can use for improvement of these grass species.
Technical Abstract: Microsatellites or simple sequence repeats (SSRs) are highly useful molecular markers for plant improvement. EST-SSR markers have a higher rate of transferability across species than genomic SSR markers and thus have a good potential for application in cross species phylogenetic studies. Our objectives were to examine the amplification of tall fescue EST-SSR markers in 12 grass species representing eight genera of four tribes from two sub-families of Poaceae and the applicability of these markers for phylogenetic analysis of grass species. About 43% of the 145 EST-SSR primer pairs produced PCR bands in all 12 grass species and had high levels of polymorphism in all forage grasses studied. Thus these markers will be useful in a variety of forage grass species including the ones tested in this study. The SSR marker data were useful in grouping the genotypes within each species. Lolium temulentum, a potential model species for cool season forage grasses, showed a close relationship with the major Festuca-Lolium species in the study. Tall wheatgrass was found closely related to hexaploid wheat thereby confirming the known taxonomic relationships between these species. While clustering the closely related species, the effectiveness of such data in evaluating distantly related species needs further investigations. The DNA sequences of selected SSR bands revealed homoplasy and sequence trees supported the phylogenetic relations based on length polymorphism of EST-SSR data. Tall fescue EST-SSR markers depicted phylogenetic relations among a wide range of cool-season forage grass species and thus are an important resource for the research community working with these grass species.