title: Association mapping of seedling resistance to spot form net blotch in a worldwide collection of barley.
abstract: Spot form net blotch (SFNB), caused by the necrotrophic fungal pathogen Pyrenophora teres f. maculata, is an important foliar disease of barley in major production regions around the world. Deployment of adequate host resistance is challenging because the virulence of P. teres f. maculata is highly variable and characterized minor-effect resistances are typically ineffective against the diverse pathogen populations. A world barley core collection consisting of 2,062 barley accessions of diverse origin and genotype were phenotyped at the seedling stage with four P. teres f. maculata isolates collected from the United States (FGO), New Zealand (NZKF2), Australia (SG1), and Denmark (DEN 2.6). Of the 2,062 barley accessions phenotyped, 1,480 were genotyped with the Illumina barley iSelect chip and passed the quality controls with 5,954 polymorphic markers used for further association mapping analysis. Genome-wide association mapping was utilized to identify and map resistance loci from the seedling disease response data and the single nucleotide polymorphism (SNP) marker data. The best among six different regression models was identified for each isolate and association analysis was performed separately for each. A total of 138 significant (-log10P value>3.0) marker-trait associations (MTA) were detected. Using a 5 cM cutoff, a total of 10, 8, 13, and 10 quantitative trait loci (QTL) associated with SFNB resistance were identified for the FGO, SG1, NZKF2, and DEN 2.6 isolates, respectively. Loci containing from 1 to 34 MTA were identified on all seven barley chromosomes with one locus at 66 to 69 cM on chromosome 2H common to all four isolates. Six distinct loci were identified by the association mapping (AM) analysis that corresponded to previously characterized SFNB resistance QTL identified by biparental population analysis (QRpt4, QRpt6, Rpt4, Rpt6, Rpt7, and a QTL on 4H that was not given a provisional gene or QTL nomenclature). The 21 putative novel loci identified may represent a broad spectrum of resistance and or susceptibility loci. This is the first comprehensive AM study to characterize SFNB resistance loci underlying broad populations of the barley host and P. teres f. maculata pathogen.
authors: First, second, fourth, and fifth authors: Department of Plant Pathology, North Dakota State University, Fargo, ND 58108-6050; third author: Department of Plant Science, North Dakota State University, Fargo, ND 58108-6050; and fourth author: U.S. Department of Agriculture-Agriculture Research Service, Red River Valley Agricultural Research Center, Cereal Crops Research Unit, Fargo, ND 58102-2765.
authors: Prabin
authors: P
authors: Tamang
authors: Anjan
authors: A
authors: Neupane
authors: Sujan
authors: S
authors: Mamidi
authors: Timothy
authors: T
authors: Friesen
authors: Robert
authors: R
authors: Brueggeman
mesh_terms: D001203:Ascomycota / Q000502:physiology*; D001315:Australia; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics*; D003718:Denmark; D060467:Disease Resistance / Q000235:genetics*; D005819:Genetic Markers / Q000235:genetics; D005838:Genotype; D001467:Hordeum / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D015810:Linkage Disequilibrium; D009520:New Zealand; D010641:Phenotype; D010935:Plant Diseases / Q000276:immunology* / Q000382:microbiology; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D040641:Quantitative Trait Loci / Q000235:genetics; D036226:Seedlings / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D014481:United States; D014774:Virulence
chemical_list: D005819:Genetic Markers