An adult plant stripe rust resistance gene maps on chromosome 7A of Australian wheat cultivar Axe.

Mehwish Kanwal,Harbans Bariana,Kerrie Forrest,Prashanth Babu,Mesfin Gessese,Urmil Bansal,Naeela Qureshi

doi:10.1007/s00122-021-03818-x

Abstract

An adult plant stripe rust resistance gene Yr75 was located on the long arm of chromosome 7A. Fine mapping of the region identified markers closely linked with Yr75. Australian wheat cultivar Axe produced resistant to moderately resistant stripe rust responses under field conditions and was exhibiting seedling responses varying from 33C to 3+ under greenhouse conditions. Experiments covering tests at different growth stages (2nd, 3rd and 4th leaf stages) demonstrated the clear expression of resistance at the 4th leaf stage under controlled-environment greenhouse conditions. A recombinant inbred line (RIL) population was developed from the Axe/Nyabing-3 (Nyb) cross. Genetic analysis of Axe/Nyb RIL population in the greenhouse at the 4th leaf stage showed monogenic inheritance of stripe rust resistance. Selective genotyping using the iSelect 90K Infinium SNP genotyping array was performed, and the resistance locus was mapped to the long arm of chromosome 7A and named Yr75. The Axe/Nyb RIL population was genotyped using a targeted genotype-by-sequencing assay, and the resistance-linked SNPs were converted into kompetitive allele-specific PCR (KASP) markers. These markers were tested on the entire Axe/Nyb RIL population, and markers sunKASP_430 and sunKASP_427 showed close association with Yr75 in the Axe/Nyb RIL population. A high-resolution mapping family of 1032 F2 plants from the Axe/Nyb cross was developed and genotyped with sunKASP_430 and sunKASP_427, and these markers flanked Yr75 at 0.3cM and 0.4cM, respectively. These markers cover 1.24Mb of the physical map of Chinese Spring, and this information will be useful for map-based cloning of Yr75.

Highlights

Stripe rust or yellow rust, caused by Puccinia striiformis f. sp. tritici (Pst), ranks high among fungal diseases of wheat worldwide
The Axe/Nyb recombinant inbred line (RIL) population was inoculated with the Pst pathotype 134 E16A+Yr17+Yr27+ under greenhouse conditions at the 2nd, 3rd, and 4th leaf stages
Infection types among resistant RILs ranged from IT1C to IT23C. These results suggested that resistance carried by Axe does not typically belong to the either of the currently defined ASR or adult plant resistance (APR) categories

Summary

Introduction

Stripe rust or yellow rust, caused by Puccinia striiformis f. sp. tritici (Pst), ranks high among fungal diseases of wheat worldwide. Tritici (Pst), ranks high among fungal diseases of wheat worldwide This disease has the potential to cause almost 1 billion AUD of losses in Australia (Murray and Brennan 2009). This disease was endemic to cooler wheat-growing regions, but in the last two decades it has adapted to relatively warmer regions causing worldwide expansion and leading to many destructive pandemics (Ali et al 2014). Experiments have been conducted on the biological control of stripe rust, but no significant reduction in severity of disease has been noted. This approach is not practically viable (Reiss and Jørgensen 2017; Feodorova-Fedotova et al 2019). Breeding for rust resistance is considered a preferred method to effectively control this disease due to its eco-friendly and economic nature (Bariana et al 2007a)

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Conclusion