title: Genetic variation, population structure and linkage disequilibrium in Switchgrass with ISSR, SCoT and EST-SSR markers.
abstract: BACKGROUND
  To evaluate genetic variation, population structure, and the extent of linkage disequilibrium (LD), 134 switchgrass (Panicum virgatumL.) samples were analyzed with 51 markers, including 16 ISSRs, 20 SCoTs, and 15 EST-SSRs.
  
  
  RESULTS
  In this study, a high level of genetic variation was observed in the switchgrass samples and they had an average Nei's gene diversity index (H) of 0.311. A total of 793 bands were obtained, of which 708 (89.28 %) were polymorphic. Using a parameter marker index (MI), the efficiency of the three types of markers (ISSR, SCoT, and EST-SSR) in the study were compared and we found that SCoT had a higher marker efficiency than the other two markers. The 134 switchgrass samples could be divided into two sub-populations based on STRUCTURE, UPGMA clustering, and principal coordinate analyses (PCA), and upland and lowland ecotypes could be separated by UPGMA clustering and PCA analyses. Linkage disequilibrium analysis revealed an average r2of 0.035 across all 51 markers, indicating a trend of higher LD in sub-population 2 than that in sub-population 1 (P< 0.01).
  
  
  CONCLUSIONS
  The population structure revealed in this study will guide the design of future association studies using these switchgrass samples.
authors.affiliation: Grassland Science Department, Sichuan Agricultural University, Chengdu, 611130 China.|IRTA. Centre de Recerca en Agrigenòmica (CSIC-IRTA-UAB), Campus UAB - Edifici CRAG, Bellaterra - Cerdanyola del Vallès, Barcelona, 08193 Spain.
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Grassland Science Department, Sichuan Agricultural University, Chengdu, 611130 China.
authors.forename: Haidong
authors.initials: H
authors.lastname: Yan
authors.affiliation: Grassland Science Department, Sichuan Agricultural University, Chengdu, 611130 China.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Jiang
authors.affiliation: Guizhou Institute of Prataculture, Guiyang, 550006 PR China.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Wang
authors.affiliation: Grassland Science Department, Sichuan Agricultural University, Chengdu, 611130 China.
authors.forename: Linkai
authors.initials: L
authors.lastname: Huang
authors.affiliation: College of Grassland Science, Nanjing Agricultural University, Nanjing, 210095 China.
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.affiliation: Grassland Science Department, Sichuan Agricultural University, Chengdu, 611130 China.
authors.forename: Xinquan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Grassland Science Department, Sichuan Agricultural University, Chengdu, 611130 China.
authors.forename: Lexin
authors.initials: L
authors.lastname: Zhang
mesh_terms: D018387:Codon, Initiator; D018744:DNA, Plant / Q000235:genetics; D060146:Ecotype; D020224:Expressed Sequence Tags; D005819:Genetic Markers; D014644:Genetic Variation; D005828:Genetics, Population; D005838:Genotype; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats; D008957:Models, Genetic; D008897:Panicum / Q000235:genetics*
chemical_list: D018387:Codon, Initiator; D018744:DNA, Plant; D005819:Genetic Markers
keywords: Genetic variation; Linkage disequilibrium; Panicum virgatum L; Population structure