Gene-specific markers for the wheat gene Lr34/Yr18/Pm38 which confers resistance to multiple fungal pathogens

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 single nucleotide polymorphism 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. AbstractThe 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 postula...

Recent emergence of the wheat Lr34 multi-pathogen resistance: insights from haplotype analysis in wheat, rice, sorghum and Aegilops tauschii

“…The tyrosine residue at position 634 of LR34sus-D is highly conserved among different ABCG proteins in various plant species (Krattinger et al 2011). Several additional Lr34 alleles have been identified at lower frequencies in the wheat genepool (Dakouri et al 2010;Lagudah et al 2009;McCallum et al 2012). However, none of these were associated with disease resistance and they either represent In this study we examined Lr34 homoeologs and orthologs in a set of wheat, rice and sorghum genotypes.…”

Comment on ‘In Turkish wheat cultivars the resistance allele of LR34 is ineffective against leaf rust’

“…The American wheat cultivar 'Jagger' for example showed presence of Lr34 using molecular markers but was classified as susceptible. Complete sequencing of the 'Jagger' Lr34 allele revealed an additional point mutation resulting in a premature stop codon and possibly a non-functional protein (Lagudah et al 2009). …”

A combination of leaf rust resistance gene Lr34 and lesion mimic gene lm significantly enhances adult plant resistance to Puccinia triticina in wheat

“…Ambiguous data were removed following visuall inspection. Lr34-specific markers, cssfr1 and cssfr2, which were designed based on a 3 bp polymorphism on exon 11 between Lr34 alleles, were amplified in Ning 7840 (Anhui 11/Aurora//Sumai 3) and its parents following the procedure described by Lagudah et al [27]. Agarose gels (1%) were used to resolve PCR products.…”

“…cssfr1 is a positive control marker for Lr34, and produced a PCR fragment of 517 bp in wheat lines carrying Lr34, but generated no products in wheat lines lacking Lr34. cssfr2 is a negative control marker for Lr34 and produced a fragment of 523 bp in wheat lines lacking Lr34 but generated no products in wheat lines carrying Lr34 [27], indicating that Lr34 in Ning 7840 was derived from Sumai 3.…”