Identification, Characterization and Mapping of LrCen, a New Leaf Rust (Puccinia triticina) Resistance Gene in Spring Wheat (Triticum aestivum)
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Date
2016
Authors
Boyce, Marley
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Abstract
Wheat leaf rust, caused by Puccinia triticina Eriks. (= P. recondita Rob. Ex Desmaz. f. sp. tritici), is the most widespread disease of wheat worldwide and causes average annual yield losses of 5 to 25%. The emergence of a new predominant race of leaf rust, TDBG, in the 2004 Canadian virulence survey led to the identification of a second leaf rust resistance gene segregating in the Thatcher-Lr1 near-isogenic differential line, RL6003, which produced an unusual mesothetic infection type. This gene was subsequently isolated in a Thatcher background and temporarily designated as LrCen (Tc-LrCen). A cross was made with a susceptible parent (Tc-LrCen/ Sumai3-lr34) and a doubled haploid (DH) mapping population was generated from the hybrids. Parental lines and 180 double haploid (DH) individuals were phenotyped with race TDBG and a 1:1 ratio was observed in the DH population. Parental lines and 94 DH individuals were genotyped with the Illumina Infinium assay using a custom iSelect 90K wheat SNP array. Two-point linkage between the phenotype and polymorphic SNP markers identified linked markers. A BLAST search of linked SNP sequences was performed against the Wheat Survey Sequence providing a putative chromosomal location of 7AL. Subsequent mapping with microsatellite markers confirmed LrCen was located on the long arm of chromosome 7A flanked by gwm344 (9.5 cM) and cfa2240 (0.6 cM) as well as a group of co-segregating SNPs also at a genetic distance of 0.6 cM. When the SNP sequences were converted to the kompetitive allele specific PCR (KASP) markers they were found to be dominant, making them less useful for marker assisted selection in populations with heterozygotes. LrCen mapped distal to Lr20; the only other Lr gene previously identified on chromosome 7AL.
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Keywords
Leaf rust, Spring wheat, Genetic mapping