Abstract
Wheat cultivar VL Gehun 892 has shown a high level of resistance against Australian Puccinia striiformis f. sp. tritici (Pst) pathotypes. In this study, it was crossed with Westonia, a susceptible wheat cultivar, and digenic segregation was observed in the derived population against Pst pathotype 134 E16A+Yr17+Yr27+. Single-gene recombinant inbred line (RIL) populations were developed from F3 families (VL Gehun 892/Westonia#1 and VLGehun 892/Westonia#4) that showed monogenic segregations with two distinct phenotypes. Single-gene segregation against Pst pathotype 134 E16A+Yr17+Yr27+ was confirmed in both F6 RIL populations. Bulked segregant analysis using a 90K Infinium SNP array placed YrVL1 in the short arm of chromosome 3D and YrVL2 in the long arm of chromosome 7B. Kompetitive allele specific polymerase chain reaction (KASP) assays were developed for the SNPs linked with YrVL1 and YrVL2 and were mapped onto the respective populations. KASP_48179 (0.6 cM proximal) and KASP_18087 (2.1 cM distal) flanked YrVL1, whereas YrVL2 was mapped between KASP_37096 (1.2 cM proximal) and KASP_2239 (3.6 cM distal). Based on their pathotypic specificities, map locations, and stages of expression, YrVL1 and YrVL2 were demonstrated to be unique loci and named Yr66 and Yr67, respectively. Markers linked with these genes showed more than 85% polymorphism when tested on a set of 89 Australian cultivars and hence could be used for the marker-assisted selection of these genes in wheat breeding programs, following checks of parental polymorphisms.
Highlights
The causal agents of rust diseases in the Puccinia species of wheat were ranked among the top 10 fungal pathogens in a survey of plant pathologists associated with the journalMolecular Plant Pathology [1]
Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) was estimated to cause A$127 million in losses in Australia [2]
Inheritance of Stripe Rust Resistance. Both VL/Wes#1 and VL/Wes#4 recombinant inbred line (RIL) populations were tested at the two-leaf stage with Pst pathotype 134E16A+Yr17+Yr27+
Summary
The causal agents of rust diseases in the Puccinia species of wheat were ranked among the top 10 fungal pathogens in a survey of plant pathologists associated with the journalMolecular Plant Pathology [1]. Stripe rust caused by Puccinia striiformis f. The deployment of resistance is the preferred option for stripe rust control due to environmental and economic considerations [3,4,5]. Genetic control can be achieved by deploying race-specific all-stage resistance (ASR) and non-race-specific adult plant resistance (APR) genes [3,6,7,8]. The deployment of a single ASR gene in commercial cultivars often leads to the breakdown of resistance due to the acquisition of virulence in the pathogen population [9,10]. New pathotypes with virulence for stripe rust resistance genes that were previously effective against the predominant pathotypes have appeared recently (pathotypes 239 E139A-Yr17+Yr33+ and 198 E16A-Yr17+YrJ+YrT+), these pathotypes carried avirulence for some previously ineffective genes.
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