Breakdown of Yr15 Resistance in the UK

Borlaug Global Rust Initiative (BGRI) 2025 Technical Workshop

Abstract:
Authors: Huw R. Davis, Tansy Chia, Hayley Rhodes, Clare M. Lewis, Andrey Korolev, Lesley Boyd, Diane G.O. Saunders, Charlotte F. Nellist and Kostya Kanyuka

The United Kingdom Cereal Pathogen Virulence Survey (UKCPVS) was established in 1967 following a major yellow rust outbreak on the previously resistant wheat variety Rothwell Perdix. Since then, Puccinia striiformis f. sp. tritici (Pst), the causal agent of yellow rust, has been routinely monitored across the UK wheat growing regions.

In spring 2025, unusually high levels of yellow rust were observed by the Niab Northern trials team on wheat varieties rated as highly resistant at both the seedling and the adult plant stages. Similar reports and samples were received from across the industry. Pathotyping of three of these early-season isolates on a wheat differential line set confirmed that all three carried virulence to Yr15 – a major, broad-spectrum, all-stage resistance gene first identified in the 1980s and widely deployed worldwide. Genotyping using KASP markers revealed that Yr15 is present in many UK AHDB Recommended List varieties previously classified as resistant at the young plant stage. Collectively these account for at least 58.7% of the UK certified seed market, excluding farm-saved seed. MARPLE diagnostics genotyping performed on two of the early isolates (from varieties Champion and KWS Dawsum) indicate that the new virulent pathotype likely represent a locally evolved variant of the European PstS10 (Warrior -) lineage, rather than a recent exotic incursion. The widespread cultivation of Yr15-carrying varieties has likely exerted strong selection pressure on the pathogen population, facilitating the emergence of virulence in the current season. Ongoing work includes transcriptome and whole genome sequencing of these isolates to investigate the underlying genetic changes associated with the breakdown of resistance.

About the Speaker:
Charlotte Nellist is a group leader in plant pathology at Niab, Cambridge, UK. She joined the Niab Group in 2014 and her research to date has focused on understanding interactions between and characterising resistance against fungal, oomycete and viral plant pathogens, across a range of crop species. She is co-lead of the United Kingdom Cereal Pathogen Virulence Survey, monitoring yellow and brown rust on wheat (and until recently, wheat and barley powdery mildew) in the UK. She also manages the pathology programmes for national variety trials delivered by Niab, including cereals, oilseeds, pulses, potatoes, sugar beet, herbage.

About the Workshop:
The 2025 BGRI Technical Workshop took place on June 18 as part of the 17th International Cereal Rusts and Powdery Mildews Conference (ICRPMC), in collaboration with the European and Mediterranean Cereal Rust Foundation (EMCRF) and the Canadian Phytopathological Society.