Improved rust watch lists for wheat released

With rust activity increasing across the UK (in several varieties), we have issued the improved and updated yellow rust and brown rust watch lists for winter wheat. Jason Pole explains how the lists highlight varieties that may get more disease at the adult plant stage than their rust ratings suggest.

The watch lists highlight winter wheat varieties that performed out of line with their Recommended Lists (RL) yellow rust or brown rust disease resistance ratings at some trial sites.

These varieties may have an elevated risk of showing more disease than the RL rating would suggest and should be monitored more closely and treated with rust-active fungicides, where disease pressure merits it.

Paul Gosling, who leads the RL project at AHDB, reflected on the performance of the watch lists at the Agronomy Conference in December.

An analysis of the yellow rust watch list over its first two seasons (2021–22) showed the lists can identify varieties at risk of losing disease rating points.

But the approach is not perfect.

Most notably, last year’s yellow rust watch list did not predict the big falls in disease ratings.

Many varieties, including those with RL 2025/26 ratings of 9, lost several rating points in the latest edition of the RL (2026/27).

The shakeup was dramatic because a new pathogen strain swept across many parts of the UK that unpicked a major yellow rust resistance gene.

The gene in question (Yr15) provided good protection against yellow rust for nearly 30 years, at both the young plant and adult plant stages.

The data that underpinned the 2025 watch list was collected up to July 2024.

It indicated that most varieties generally performed as expected, including at the trial sites first impacted by the Yr15-breaking strain in the following season.

The problematic new strain arrived too late to cause major issues in the harvest 2024 trials; it may even have arrived after crops had senesced.

The first confirmed recording of the new strain was in November 2024, although its significance was not recognised at the time.

It is likely to have initially spread early in the life of the harvest 2025 crop in the northeast (the disease epicentre), potentially multiplying on cereal volunteers first.

This perfectly primed the outbreak and highlights the watch lists’ Achilles' heel: They can’t detect what is not there.

However, we can improve the watch lists to provide better data on what is present.

The 2026 watch lists use an improved method that accounts better for trial-site disease pressures at the three worst-performing trial sites (in terms of yellow rust or brown rust levels).

We use the disease data to create worst-case-scenario disease ratings.

The closer a variety aligns with its current RL disease rating, the higher it ranks on the watch list (and vice versa).

Some varieties with high levels of resistance (8) in RL 2026/27 rank near the bottom of the 2026 yellow rust watch list and should be monitored more closely.

As the new race disrupted the UK yellow rust population, it could take a few seasons for things to settle (so expect the unexpected).

Thankfully, the brown rust watch list shows that this population was relatively stable in 2025.

The RL rust disease ratings indicate adult plant resistance (on a 1–9 scale).

Unlike adult plant resistance, young plant resistance to yellow rust is effective at all growth stages.

Since RL 2023/24, the young plant resistance or susceptibility status has been presented alongside the adult plant resistance ratings.

Young plant resistance is mainly determined by UK Cereal Pathogen Virulence Survey (UKCPVS) growth room infection tests based on yellow rust isolates collected from the field.

A variety is classified as susceptible if it is infected by any strain in the last three years.

Additionally, RL yellow rust disease data from before stem extension and UKCPVS spring-sown winter wheat variety trial results are used to set the resistance status.

Only one variety on RL 2026/27 has yellow rust resistance at this stage (new addition RGT Guardsman).

With the strong shift in the 2025 pathogen population, the RL 2026/27 rating calculations only use data collected in 2025, rather than the standard three-year data set (we also made other changes to provide the most robust ratings).

This means the ratings better reflect results seen in RL trials in 2025, while still incorporating results with older strains of yellow rust that continued to dominate in trials in the south of England and South Wales in 2025.

The Yr15 resistance gene provided an important line of defence against yellow rust, with the impact softened by other resistance genes to various degrees.

With Yr15 still present across a large UK winter wheat area, yellow rust will require extra attention this season.

Varieties susceptible at the young plant stage may need yellow rust treatment during the T0–T2 fungicide period, even if they have a high level of adult plant resistance (ratings 8 or 9).

For the most susceptible varieties (ratings 3 or 4), growers should even consider a pre-T0 spray, where there is active yellow rust.

However, it is important to consider the maximum permitted number of applications for some fungicide products and classes across the programme. If in doubt, consult a BASIS-qualified agronomist.

Check the disease resistance information in the RL booklet and the rankings in the watch lists to guide your treatment decisions at T0 (and beyond).

If you observe unexpected rust symptoms (more than the disease rating suggests), send a leaf sample for free to UKCPVS for analysis.

Long before modern plant breeding, farmers selected what grew well, which created unique landraces.

A.E. Watkins collected over a thousand of such wheat landraces from 32 countries about one hundred years ago, with most still in the collection today.

This phenotypically diverse resource includes 33 lines with resistance to the diverse Warrior group of yellow rust races that currently dominate European population, including an impressive 32 lines that resist the Yr15-breaking strain.

Researchers at the John Innes Centre, who manage the landrace collection and identified the novel sources of resistance, have been awarded a grant to help get this resistance into the wheat breeding pipeline.

Niab will also provide wheat disease monitoring expertise, including the rapid screening of plant lines to identify genetic resistance to yellow rust and monitoring signs of fungicide resistance in yellow rust isolates.