title: Genetic structure of Thai rice and rice accessions obtained from the International Rice Research Institute.
abstract: BACKGROUND
  Although the genetic structure of rice germplasm has been characterized worldwide, few studies investigated germplasm from Thailand, the world's largest exporter of rice. Thailand and the International Rice Research Institute (IRRI) have diverse collections of rice germplasm, which could be used to develop breeding lines with desirable traits. This study aimed to investigate the level of genetic diversity and structures of Thai and selected IRRI germplasm. Understanding the genetic structure and relationships among these germplasm will be useful for parent selection used in rice breeding programs.
  
  
  RESULTS
  From the 98 InDel markers tested for single copy and polymorphism, 19 markers were used to evaluate 43 Thai and 57 IRRI germplasm, including improved cultivars, breeding lines, landraces, and 5 other Oryza species. The Thai accessions were selected from all rice ecologies such as irrigated, deep water, upland, and rainfed lowland ecosystems. The IRRI accessions were groups of germplasm having agronomic desirable traits, including temperature-sensitive genetic male sterility (TGMS), new plant type, early flowering, and biotic and abiotic stress resistances. Most of the InDel markers were genes with diverse functions. These markers produced the total of 127 alleles for all loci, with a mean of 6.68 alleles per locus, and a mean Polymorphic Information Content (PIC) of 0.440. Genetic diversity of Thai rice were 0.3665, 0.4479 and 0.3972 for improved cultivars, breeding lines, and landraces, respectively, while genetic diversity of IRRI improved and breeding lines were 0.3272 and 0.2970, respectively. Cluster, structure, and differentiation analyses showed six distinct groups: japonica, TGMS, deep-water, IRRI germplasm, Thai landraces and breeding lines, and other Oryza species.
  
  
  CONCLUSIONS
  Thai and IRRI germplasm were significantly different. Thus, they can be used to broaden the genetic base and trait improvements. Cluster, structure, and differentiation analyses showed concordant results having six distinct groups, in agreement with their development, and ecologies.
authors.affiliation: Laboratory of Plant Molecular Genetics, National Center for Genetic Engineering and Biotechnology, Pathum thani, 12120, Thailand.
authors.forename: Sriprapai
authors.initials: S
authors.lastname: Chakhonkaen
authors.affiliation: Laboratory of Plant Molecular Genetics, National Center for Genetic Engineering and Biotechnology, Pathum thani, 12120, Thailand.
authors.forename: Keasinee
authors.initials: K
authors.lastname: Pitnjam
authors.affiliation: Department of Biotechnology, Faculty of Science and Technology, Thammasart University, Rangsit, Pathum thani, 12120, Thailand.
authors.forename: Wachira
authors.initials: W
authors.lastname: Saisuk
authors.affiliation: Department of Biotechnology, Faculty of Science and Technology, Thammasart University, Rangsit, Pathum thani, 12120, Thailand.
authors.forename: Kittipat
authors.initials: K
authors.lastname: Ukoskit
authors.affiliation: Laboratory of Plant Molecular Genetics, National Center for Genetic Engineering and Biotechnology, Pathum thani, 12120, Thailand. amorntip.mua@biotec.or.th.
authors.forename: Amorntip
authors.initials: A
authors.lastname: Muangprom
keywords: Genetic diversity; Germplasm evaluation; InDel marker; Oryza sativa; Population structure; Temperature sensitive genetic male-sterile