title: Molecular mapping of the Pi2/9 allelic gene Pi2-2 conferring broad-spectrum resistance to Magnaporthe oryzae in the rice cultivar Jefferson.
abstract: BACKGROUND
  Utilization of broad-spectrum resistance (R) genes is an effective and economical strategy to control the fungal pathogen Magnaporthe oryzae, the causal agent of the rice blast disease. Among the cloned blast resistance genes, Pi9, Pi2 and Piz-t confer broad-spectrum resistance to diverse M. oryzae isolates and were isolated from the Pi2/9 locus on chromosome 6. Identification and isolation of additional R genes with different resistance spectra from this locus will provide novel genetic resources for better control of this important rice disease.
  
  
  RESULTS
  In this study, we identified a dominant R gene, Pi2-2, at the Pi2/9 locus from Jefferson, an elite U.S. rice cultivar, through genetic and physical mapping. Inoculation tests showed that Jefferson has different resistant specificities to M. oryzae isolates compared rice lines with the Pi9, Pi2 and Piz-t genes. Fine mapping delimited Pi2-2 to a 270-kb interval between the markers AP5659-3 and RM19817, and this interval contains three nucleotide-binding site-leucine-rich repeat (NBS-LRR) genes in the Nipponbare genome. Five bacterial artificial chromosome (BAC) clones spanning the region were identified, and a BAC contig covering the Pi2-2 locus was constructed.
  
  
  CONCLUSIONS
  We identified a new allelic gene at the Pi2/9 locus and fine-mapped the gene within a 270-kb region. Our results provide essential information for the isolation of the Pi2-2 gene and tightly linked DNA markers for rice blast resistance breeding.
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.|State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
authors.forename: Nan
authors.initials: N
authors.lastname: Jiang
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.|State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Li
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Wu
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Liqun
authors.initials: L
authors.lastname: Wu
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Suhua
authors.initials: S
authors.lastname: Wang
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Dan
authors.initials: D
authors.lastname: Wang
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Wen
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Liang
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Pingyong
authors.initials: P
authors.lastname: Sun
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.|State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China.
authors.forename: Jinling
authors.initials: J
authors.lastname: Liu
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Liangying
authors.initials: L
authors.lastname: Dai
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China.
authors.forename: Zhilong
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Meizhong
authors.initials: M
authors.lastname: Luo
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China. xionglun@yahoo.com.
authors.forename: Xionglun
authors.initials: X
authors.lastname: Liu
authors.affiliation: Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, College of Agronomy, College of Bio-Safety Science and Technology, Hunan Agricultural University, Changsha, 410128, China. wang.620@osu.edu.|State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, 100193, China. wang.620@osu.edu.|Department of Plant Pathology, Ohio State University, Columbus, Ohio, 43210, USA. wang.620@osu.edu.
authors.forename: Guo-Liang
authors.initials: GL
authors.lastname: Wang
keywords: BAC clones; Mapping; Pi2/9 locus; Resistance gene; Rice blast