Abstract
Genetic resistance is the most effective approach to managing wheat leaf rust. The aim of this study was to characterize seedling and adult plant leaf rust resistance of a world wheat collection. Using controlled inoculation with ten races of Puccinia triticina, 14 seedling resistance genes were determined or postulated to be present in the collection. Lr1, Lr3, Lr10 and Lr20 were the most prevalent genes around the world while Lr9, Lr14b, Lr3ka and/or Lr30 and Lr26 were rare. To confirm some gene postulations, the collection was screened with gene-specific molecular markers for Lr1, Lr10, Lr21 and Lr34. Although possessing the Lr1 and/or Lr10 gene-specific marker, 51 accessions showed unexpected high infection types to P. triticina race BBBD. The collection was tested in the field, where rust resistance ranged from nearly immune or highly resistant with severity of 1 % and resistant host response to highly susceptible with severity of 84 % and susceptible host response. The majority of the accessions possessing the adult plant resistance (APR) gene Lr34 had a maximum rust severity of 0–35 %, similar to or better than accession RL6058, a Thatcher-Lr34 near-isogenic line. Many accessions displayed an immune response or a high level of resistance under field conditions, likely as a result of synergy between APR genes or between APR and seedling resistance genes. However, accessions with three or more seedling resistance genes had an overall lower field severity than those with two or fewer. Immune or highly resistant accessions are potential sources for improvement of leaf rust resistance. In addition, some lines were postulated to have known but unidentified genes/alleles or novel genes, also constituting potentially important sources of novel resistance.Electronic supplementary materialThe online version of this article (doi:10.1007/s11032-013-9899-8) contains supplementary material, which is available to authorized users.
Highlights
Leaf rust, caused by the fungal pathogen Puccinia triticina Eriks., has been the most prevalent disease in wheat-producing areas (Kolmer 2005)
Gene postulation accompanied by molecular marker data were applied to determine seedling resistance genes in the WC
Gene-specific markers are more accurate but, as we discovered for Lr1 and Lr10, they may not correlate perfectly with the phenotype
Summary
Leaf rust, caused by the fungal pathogen Puccinia triticina Eriks., has been the most prevalent disease in wheat-producing areas (Kolmer 2005). This fungus is adapted to a wide range of environments and it can co-exist with wheat wherever it is grown (Winzeler et al 2000). Leaf rust resistance genes named Lr1 to Lr68 have been characterized in bread wheat, durum wheat and diploid wheat species. These genes are located on 20 of the 21 chromosomes of hexaploid wheat (McIntosh et al 1995, 2007; McCallum et al 2012). Most Lr genes confer race-specific resistance and follow the gene-forgene concept leading to a hypersensitive response (HR)
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