ARS | Publication request: Gene-specific markers for the wheat gene Lr34/Yr18/Pm38 which confers resistance to multiple fungal pathogens

Submitted to: Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 13, 2009
Publication Date: July 4, 2009
Citation: Lagudah, E.S., Krattinger, S.G., Herrera-Foessel, S., Singh, R.P., Huerta-Espino, J., Spielmeyer, W., Brown Guedira, G.L., Selter, L.L., Keller, B. 2009. Gene-specific markers for the wheat gene Lr34/Yr18/Pm38 which confers resistance to multiple fungal pathogens. Theoretical and Applied Genetics. 119:889-898.

Interpretive Summary: Multiple fungal diseases, including leaf rust, stripe rust and powdery mildew, can cause yield losses in wheat in temperate growing regions of the world. In the Eastern United States, these diseases cause grain yield reductions, and can significantly reduce flour yield and adversely affect other aspects of grain quality. The use of resistant cultivars is an effective, economical and environmentally safe approach to eliminate the use of fungicides and to reduce production losses due to foliar diseases. In this study, we analyzed a recently cloned gene designated Lr34/Yr18/Pm38 that confers partial and durable resistance against the leaf rust, stripe rust and powdery mildew diseases. Diagnostic DNA markers or tags for this resistance gene were identified. These molecular tags can be used by wheat breeders to determine if cultivars have this durable resistance gene and to select new resistant varieties.

Technical Abstract: The locus Lr34/Yr18/Pm38 confers partial and durable resistance against the devastating fungal pathogens leaf rust, stripe rust, and powdery mildew. In previous studies, this broad-spectrum resistance was shown to be controlled by a single gene which encodes a putative ATP-binding cassette transporter. Alleles of resistant and susceptible cultivars differed by only three sequence polymorphisms and the same resistance haplotype was found in the three independent breeding lineages of Lr34/Yr18/Pm38. Hence, we used these conserved sequence polymorphisms as templates to develop diagnostic molecular markers that will assist selection for durable multi-pathogen resistance in breeding programs. Five allele-specific markers (cssfr1 – cssfr5) were developed based on a 3 bp deletion in exon 11 of the Lr34-gene, and one marker (cssfr6) was derived from a SNP in exon 12. Validation of reference genotypes, well characterized for the presence or absence of the Lr34/Yr18/Pm38 resistance locus, demonstrated perfect diagnostic values for the newly developed markers. By testing the new markers on a larger set of wheat cultivars, a third Lr34 haplotype, not described so far, was discovered in some European winter wheat and spelt material. Some cultivars with uncertain Lr34 status were re-assessed using the newly derived markers. Unambiguous identification of the Lr34 gene aided by the new markers has revealed that some wheat cultivars incorrectly postulated as having Lr34 may possess as yet uncharacterised loci for adult plant leaf and stripe rust resistance.