Genetic mapping and marker development for resistance of wheat against the root lesion nematode Pratylenchus neglectus

Dimanthi V Jayatilake,Haydn Kuchel,Diane E Mather,Alan C Mckay,Elise J Tucker,Harbans Bariana,James Edwards,Ken Chalmers

doi:10.1186/1471-2229-13-230

Abstract

BackgroundThe Rlnn1 locus, which resides on chromosome 7A of bread wheat (Triticum aestivum L.) confers moderate resistance against the root lesion nematode Pratylenchus neglectus. Prior to this research, the exact linkage relationships of Rlnn1 with other loci on chromosome 7A were not clear and there were no simple codominant markers available for selection of Rlnn1 in wheat breeding. The objectives of the research reported here were to (1) develop an improved genetic map of the Rlnn1 region of chromosome 7A and (2) develop molecular markers that could be used in marker-assisted selection to improve resistance of wheat against P. neglectus.ResultsA large-effect quantitative trait locus (QTL) for resistance against P. neglectus was genetically mapped using a population of Excalibur/Kukri doubled haploid lines. This QTL coincides in position with the rust resistance gene(s) Lr20/Sr15, the phytoene synthase gene Psy-A1 and 10 molecular markers, including five new markers designed using wheat-rice comparative genomics and wheat expressed sequence tags. Two of the new markers are suitable for use as molecular diagnostic tools to distinguish plants that carry Rlnn1 and Lr20/Sr15 from those that do not carry these resistance genes.ConclusionsThe genomic location of Rlnn1 was confirmed to be in the terminal region of the long arm of chromosome 7A. Molecular markers were developed that provide simple alternatives to costly phenotypic assessment of resistance against P. neglectus in wheat breeding. In Excalibur, genetic recombination seems to be completely suppressed in the Rlnn1 region.

Highlights

The Rlnn1 locus, which resides on chromosome 7A of bread wheat (Triticum aestivum L.) confers moderate resistance against the root lesion nematode Pratylenchus neglectus
Resistance against leaf rust, stem rust and Pratylenchus neglectus Evaluation of disease responses against the P. triticina pathotype 104–2,3,6,7 and the P. graminis f. sp. tritici pathotype 98–1,2,(3),5,6 indicated that Excalibur and 98 Excalibur/Kukri doubled haploid (DH) lines carry Lr20/ Sr15 resistance, while Kukri and 74 other Excalibur/Kukri DH lines are susceptible to both rust pathogens
The research reported here has clarified the position of the Rlnn1 locus for resistance against the root lesion nematode P. neglectus, by using a large wheat population to map Rlnn1 as a quantitative trait locus (QTL), rather than relying upon consensus mapping from small samples

Summary

Introduction

The Rlnn locus, which resides on chromosome 7A of bread wheat (Triticum aestivum L.) confers moderate resistance against the root lesion nematode Pratylenchus neglectus. P. neglectus moves in and out of roots, feeding as it moves through the root cortex It causes lesions on roots, stunts plant growth and can significantly reduce crop yield. Williams et al [3] attributed the P. neglectus resistance of these cultivars to a locus (Rlnn1) on the long arm of chromosome 7A (7AL). They estimated Rlnn to be 9.1 cM distal to the gene Lr20, which confers resistance against leaf rust (Puccinia triticina). Lr20 has in turn been reported to co-segregate with Sr15 and Pm1 [4,5], which confer resistance against stem rust (Puccinia graminis f. sp. tritici) and powdery mildew (Blumeria graminis f. sp. tritici), respectively

Methods

Results

Discussion

Conclusion