title: Characterization of Lr75: a partial, broad-spectrum leaf rust resistance gene in wheat.
abstract: Here, we describe a strategy to improve broad-spectrum leaf rust resistance by marker-assisted combination of two partial resistance genes. One of them represents a novel partial adult plant resistance gene, named Lr75. Leaf rust caused by the fungal pathogen Puccinia triticina is a damaging disease of wheat (Triticum aestivum L.). The combination of several, additively-acting partial disease resistance genes has been proposed as a suitable strategy to breed wheat cultivars with high levels of durable field resistance. The Swiss winter wheat cultivar 'Forno' continues to show near-immunity to leaf rust since its release in the 1980s. This resistance is conferred by the presence of at least six quantitative trait loci (QTL), one of which is associated with the morphological trait leaf tip necrosis. Here, we used a marker-informed strategy to introgress two 'Forno' QTLs into the leaf rust-susceptible Swiss winter wheat cultivar 'Arina'. The resulting backcross line 'ArinaLrFor' showed markedly increased leaf rust resistance in multiple locations over several years. One of the introgressed QTLs, QLr.sfr-1BS, is located on chromosome 1BS. We developed chromosome 1B-specific microsatellite markers by exploiting the Illumina survey sequences of wheat cv. 'Chinese Spring' and mapped QLr.sfr-1BS to a 4.3 cM interval flanked by the SSR markers gwm604 and swm271. QLr.sfr-1BS does not share a genetic location with any of the described leaf rust resistance genes present on chromosome 1B. Therefore, QLr.sfr-1BS is novel and was designated as Lr75. We conclude that marker-assisted combination of partial resistance genes is a feasible strategy to increase broad-spectrum leaf rust resistance. The identification of Lr75 adds a novel and highly useful gene to the small set of known partial, adult plant leaf rust resistance genes.
authors.affiliation: Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland.
authors.forename: Jyoti
authors.initials: J
authors.lastname: Singla
authors.affiliation: Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland.
authors.forename: Linda
authors.initials: L
authors.lastname: Lüthi
authors.affiliation: Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Wicker
authors.affiliation: Faculty of Agriculture, Food and Natural Resources, The University of Sydney PBI-Cobbitty, Private Bag 4011, Narellan, NSW, 2567, Australia.
authors.forename: Urmil
authors.initials: U
authors.lastname: Bansal
authors.affiliation: Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland.
authors.forename: Simon G
authors.initials: SG
authors.lastname: Krattinger
authors.affiliation: Department of Plant and Microbial Biology, University of Zurich, Zollikerstrasse 107, 8008, Zurich, Switzerland. bkeller@botinst.uzh.ch.
authors.forename: Beat
authors.initials: B
authors.lastname: Keller
mesh_terms: D001487:Basidiomycota; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D060467:Disease Resistance / Q000235:genetics*; D017343:Genes, Plant; D008040:Genetic Linkage; D005819:Genetic Markers; D018895:Microsatellite Repeats; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D040641:Quantitative Trait Loci; D014908:Triticum / Q000235:genetics* / Q000382:microbiology
chemical_list: D005819:Genetic Markers