title: Genetic diversity and origin of weedy rice (Oryza sativa f. spontanea) populations found in North-eastern China revealed by simple sequence repeat (SSR) markers.
abstract: OBJECTIVE
  Weedy rice (Oryza sativa f. spontanea) is one of the most notorious weeds occurring in rice-planting areas worldwide. The objectives of this study are to determine the genetic diversity and differentiation of weedy rice populations from Liaoning Province in North-eastern China and to explore the possible origin of these weedy populations by comparing their genetic relationships with rice varieties (O. sativa) and wild rice (O. rufipogon) from different sources.
  
  
  METHODS
  Simple sequence repeat (SSR) markers were used to estimate the genetic diversity of 30 weedy rice populations from Liaoning, each containing about 30 individuals, selected rice varieties and wild O. rufipogon. Genetic differentiation and the relationships of weedy rice populations were analysed using cluster analysis (UPGMA) and principle component analysis (PCA).
  
  
  RESULTS
  The overall genetic diversity of weedy rice populations from Liaoning was relatively high (H(e) = 0.313, I = 0.572), with about 35 % of the genetic variation found among regions. The Liaoning weedy rice populations were closely related to rice varieties from Liaoning and japonica varieties from other regions but distantly related to indica rice varieties and wild O. rufipogon.
  
  
  CONCLUSIONS
  Weedy rice populations from Liaoning are considerably variable genetically and most probably originated from Liaoning rice varieties by mutation and intervarietal hybrids. Recent changes in farming practices and cultivation methods along with less weed management may have promoted the re-emergence and divergence of weedy rice in North-eastern China.
authors.affiliation: Ministry of Education Key Laboratory for Biodiversity Science and Ecological Engineering, Institute of Biodiversity Science, Fudan University Shanghai 200433, China.
authors.forename: Qianjin
authors.initials: Q
authors.lastname: Cao
authors.forename: Bao-Rong
authors.initials: BR
authors.lastname: Lu
authors.forename: Hui
authors.initials: H
authors.lastname: Xia
authors.forename: Jun
authors.initials: J
authors.lastname: Rong
authors.forename: Francesco
authors.initials: F
authors.lastname: Sala
authors.forename: Alberto
authors.initials: A
authors.lastname: Spada
authors.forename: Fabrizio
authors.initials: F
authors.lastname: Grassi
mesh_terms: D000383:Agriculture; D002681:China; D005819:Genetic Markers / Q000235:genetics; D014644:Genetic Variation; D012275:Oryza / Q000145:classification* / Q000235:genetics*; D010802:Phylogeny; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics*
chemical_list: D005819:Genetic Markers