title: Molecular mapping of qualitative and quantitative loci for resistance to Leptosphaeria maculans causing blackleg disease in canola (Brassica napus L.).
abstract: Blackleg, caused by Leptosphaeria maculans, is one of the most important diseases of oilseed and vegetable crucifiers worldwide. The present study describes (1) the construction of a genetic linkage map, comprising 255 markers, based upon simple sequence repeats (SSR), sequence-related amplified polymorphism, sequence tagged sites, and EST-SSRs and (2) the localization of qualitative (race-specific) and quantitative (race non-specific) trait loci controlling blackleg resistance in a doubled-haploid population derived from the Australian canola (Brassica napus L.) cultivars Skipton and Ag-Spectrum using the whole-genome average interval mapping approach. Marker regression analyses revealed that at least 14 genomic regions with LOD ≥ 2.0 were associated with qualitative and quantitative blackleg resistance, explaining 4.6-88.9 % of genotypic variation. A major qualitative locus, designated RlmSkipton (Rlm4), was mapped on chromosome A7, within 0.8 cM of the SSR marker Xbrms075. Alignment of the molecular markers underlying this QTL region with the genome sequence data of B. rapa L. suggests that RlmSkipton is located approximately 80 kb from the Xbrms075 locus. Molecular marker-RlmSkipton linkage was further validated in an F(2) population from Skipton/Ag-Spectrum. Our results show that SSR markers linked to consistent genomic regions are suitable for enrichment of favourable alleles for blackleg resistance in canola breeding programs.
authors.affiliation: EH Graham Centre for Agricultural Innovation, NSW Department of Primary Industries and Charles Sturt University, Wagga Wagga Agricultural Institute, PMB, Wagga Wagga, NSW 2650, Australia.
authors.forename: Rosy
authors.initials: R
authors.lastname: Raman
authors.forename: Belinda
authors.initials: B
authors.lastname: Taylor
authors.forename: Steve
authors.initials: S
authors.lastname: Marcroft
authors.forename: Jiri
authors.initials: J
authors.lastname: Stiller
authors.forename: Paul
authors.initials: P
authors.lastname: Eckermann
authors.forename: Neil
authors.initials: N
authors.lastname: Coombes
authors.forename: Ata
authors.initials: A
authors.lastname: Rehman
authors.forename: Kurt
authors.initials: K
authors.lastname: Lindbeck
authors.forename: David
authors.initials: D
authors.lastname: Luckett
authors.forename: Neil
authors.initials: N
authors.lastname: Wratten
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Batley
authors.forename: David
authors.initials: D
authors.lastname: Edwards
authors.forename: Xiaowu
authors.initials: X
authors.lastname: Wang
authors.forename: Harsh
authors.initials: H
authors.lastname: Raman
mesh_terms: D000483:Alleles; D001203:Ascomycota / Q000502:physiology*; D029688:Brassica napus / Q000235:genetics* / Q000276:immunology / Q000382:microbiology*; D002874:Chromosome Mapping / Q000379:methods*; D032461:Chromosomes, Plant / Q000235:genetics; D060467:Disease Resistance / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics; D008040:Genetic Linkage; D056426:Genetic Loci / Q000235:genetics; D010641:Phenotype; D010935:Plant Diseases / Q000235:genetics* / Q000276:immunology / Q000382:microbiology; D011110:Polymorphism, Genetic; D040641:Quantitative Trait Loci / Q000235:genetics*; D015203:Reproducibility of Results