title: Tomato defense to Oidium neolycopersici: dominant Ol genes confer isolate-dependent resistance via a different mechanism than recessive ol-2.
abstract: Tomato powdery mildew caused by Oidium neolycopersici has become a globally important disease of tomato (Lycopersicon esculentum). To study the defense responses of tomato triggered by tomato powdery mildew, we first mapped a set of resistance genes to O. neolycopersici from related Lycopersicon species. An integrated genetic map was generated showing that all the dominant resistance genes (Ol-1, Ol-3, Ol-4, Ol-5, and Ol-6) are located on tomato chromosome 6 and are organized in three genetic loci. Then, near-isogenic lines (NIL) were produced that contain the different dominant Ol genes in a L. esculentum genetic background. These NIL were used in disease tests with local isolates of O. neolycopersici in different geographic locations, demonstrating that the resistance conferred by different Ol genes was isolate-dependent and, hence, may be race-specific. In addition, the resistance mechanism was analyzed histologically. The mechanism of resistance conferred by the dominant Ol genes was associated with hypersensitive response, which varies in details depending on the Ol-gene in the NIL, while the mechanism of resistance governed by the recessive gene ol-2 on tomato chromosome 4 was associated with papillae formation.
authors.affiliation: Laboratory of Plant Breeding, Wageningen University, 6700 AJ Wageningen, The Netherlands. bai.yuling@wur.nl
authors.forename: Yuling
authors.initials: Y
authors.lastname: Bai
authors.forename: Ron
authors.initials: R
authors.lastname: van der Hulst
authors.forename: Guusje
authors.initials: G
authors.lastname: Bonnema
authors.forename: Thierry C
authors.initials: TC
authors.lastname: Marcel
authors.forename: Fien
authors.initials: F
authors.lastname: Meijer-Dekens
authors.forename: Rients E
authors.initials: RE
authors.lastname: Niks
authors.forename: Pim
authors.initials: P
authors.lastname: Lindhout
mesh_terms: D001203:Ascomycota / Q000235:genetics / Q000472:pathogenicity*; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D005799:Genes, Dominant; D017343:Genes, Plant; D005819:Genetic Markers; D005936:Glucans / Q000235:genetics*; D015810:Linkage Disequilibrium; D008126:Lod Score; D018551:Solanum lycopersicum / Q000235:genetics* / Q000382:microbiology; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D030821:Plants, Genetically Modified; D012150:Polymorphism, Restriction Fragment Length; D040641:Quantitative Trait Loci
chemical_list: D005819:Genetic Markers; D005936:Glucans; C074376:OL 2