2025/09/30 by Helena Davis, Tansy Chia, H. Rhodes +8 · 1 voice
Agricultural and Biological Sciences · Biochemistry, Genetics and Molecular Biology · #Wheat and Barley Genetics and Pathology #Plant Disease Resistance and Genetics #Yeasts and Rust Fungi Studies
paper · pdf · doi:10.1002/ndr2.70067
openalex publication_date 2025/09/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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, virulence in Puccinia striiformis f. sp. tritici (Pst), the causal agent of yellow rust, has been routinely monitored across the UK. In late winter to early spring 2025, unusually high levels of yellow rust infections on winter wheat varieties previously rated as highly resistant at both seedling and adult plant stages were observed in the counties of Northumberland and Tyne and Wear (Figure 1a). This indicated a potential major resistance breakdown, a concern soon confirmed by reports from across the agricultural industry. Importantly, disease persisted in many of these varieties to the adult plant stage (Figure 1b,c). Through the UKCPVS, urediniospores were multiplied from infected wheat samples by inoculation onto plants of the universally susceptible variety Victo maintained under controlled environment conditions until sporulation was observed. Following multiplication, three early-season Pst isolates (WYR25-001, WYR025-025 and WYR25-034) recovered from previously highly resistant varieties KWS Dawsum, Champion and KWS Palladium were virulence phenotyped on a set of 18 wheat differential lines with known yellow rust resistance genes (Yr), revealing that all were virulent to Yr15 (Figure 2; data not shown). The Yr15 resistance gene, first introgressed into bread wheat (Triticum aestivum) from wild emmer (Triticum dicoccoides) in the late 1980s (Gerechter-Amitai et al. 1989) and widely deployed in breeding since the late 1990s, has provided nearly complete, broad-spectrum, all-stage resistance against Pst for over three decades. Subsequent genotypic analysis through full transcriptome sequencing (Hubbard et al. 2015) of two Yr15-virulent Pst isolates (WYR25-001 and WYR25-025) confirmed these likely evolved from diversification within the PstS10/Warrior(-) lineage, rather than through an exotic incursion (Figure 3). Genotyping of over 95% of the winter wheat varieties (n = 36) on the Agriculture and Horticulture Development Board (AHDB) 2024/25 and 2025/26 Recommended Lists (RL) using molecular markers diagnostic of Yr15 (Ramirez-Gonzalez et al. 2015; Klymiuk et al. 2018) revealed that all 12 varieties previously classified as fully resistant at the young plant stage contained this gene (Figure 4). The Yr15-containing AHDB RL varieties were amongst the most widely grown and collectively accounted for at least 49% of the UK-certified seed market, excluding farm-saved seed, in the 2024–25 season (Table 1). While only two solitary instances of Yr15-virulent Pst isolates have been reported globally, without further spread (Hovmøller and Justesen 2007; Ali et al. 2014), we now report the first large-scale breakdown of Yr15, which has manifested as a severe epidemic across the north and east of England, from the Scottish borders to Norfolk. The widespread cultivation of Yr15-carrying varieties that we uncovered was likely the key factor underlying the emergence of Yr15-virulence in Pst, reflecting strong selection pressure exerted on the pathogen population. We thank numerous colleagues and volunteers for submitting diseased wheat samples, Adam Donalson, Alicia Farmer and Janet Adams for their technical assistance, and the UK Agriculture and Horticulture Development Board for funding the UKCPVS project (21120034a).