Using varieties to mellow yellow rust in winter wheat

Jason Pole, AHDB Technical Content Manager, explains how wheat yellow rust gets special treatment at AHDB.

A combination of varietal resistance and well-timed fungicide applications can help prevent unacceptable economic losses to yellow rust in winter wheat.

As the pathogen is highly diverse and adaptable, it can occasionally result in unexpectedly high disease levels in some varieties.

This is why our activity goes far beyond producing disease resistance ratings in the Recommended Lists for cereal and oilseeds (RL).

RL yellow rust disease resistance information is published for two broad stages: young plant and adult plant.

Despite its name, young plant resistance is effective at all growth stages, although its influence is clearest before adult plant stage resistance kicks in.

We have published information indicating whether a young plant is resistant (r) or susceptible (s) for each variety in the RL since 2023/24 (although the data has been published online for much longer).

Adult plant resistance lives up to its name, as it does not start until around stem extension (with the precise timing dependant on the variety and environmental conditions).

The RL disease resistance rating scale – 1 (least resistant) to 9 (most resistant) – is based on the adult type of resistance.

Some varieties that are susceptible at the young plant stage develop adult plant resistance to various degrees.

This includes some varieties with high disease resistance ratings (8 or 9), which can jangle the nerves, especially when early disease pressure is high.

In the winter wheat recommended list (2025/26), most varieties (25/38) are susceptible at the young plant stage.

Such varieties are more likely to require treatment for the disease during the T0–T2 fungicide period, even if they have a high disease resistance rating.

In the latest RL (2025/26), young plant resistance information was mainly derived from United Kingdom Cereal Pathogen Virulence Survey (UKCPVS) growth room infection tests.

In these controlled conditions, varieties are challenged with a carefully curated set of yellow rust strains (isolates).

Until recently, the UKCPVS tests used five strains, but this has now been increased to better reflect the diversity in the yellow rust pathogen population.

Last year, 18 strains (gathered from commercial crops in 2024) were used in these tests, with a variety classified as susceptible if it was infected by any strain.

Additional data from RL trials (from before stem extension) is used to validate the young plant resistance statuses.

Following a successful pilot in 2024, the UKCPVS project will now also include field trials with the sole purpose of gathering young plant resistance data.

Using the full set of RL winter wheat varieties and candidates, UKCPVS will drill these trials in February or March (weather permitting) at sites traditionally associated with high yellow rust pressures.

The idea is that crops reach the young plant stage when infection pressures are naturally high.

To boost pressure further, the trials will also be artificially inoculated with yellow rust (multiple isolates) with a highly susceptible variety grown (between the plots) to spread the disease.

The results will help detect any susceptibility missed in growth room tests.

UKCPVS also conducts growth room tests for brown rust, where the story is simpler. All winter wheat varieties on the current RL are susceptible to brown rust at the young plant stage, except for RGT Goldfinch. Most varieties develop a moderate level of adult plant resistance.

The 1–9 disease resistance ratings are based on a three-year data set and reflect average resistance (across trial sites and years) on adult plants.

The annually updated watch lists for yellow rust (launched in 2021) and brown watch (launched in 2023) consider how varieties at their worst-performing sites (for the respective diseases) perform relative to their disease ratings.

Where a high RL disease resistance rating appears to be less resistant in the watch list, it should be monitored more closely.

An analysis of the yellow rust watch list’s performance after the first two years indicated that the approach works.

The most resistant varieties on the watch list typically had stable or small falls in resistance in the next edition of the RL.

Conversely, the least resistant varieties on the watch list were associated with the largest falls (although not all such varieties saw falls).

The watch lists were updated today (27 February 2025), with most varieties performing as expected from their RL ratings.

UKCPVS has coordinated the monitoring of UK cereal pathogen populations since 1967, which is still its core aim almost 60 years later.

This spring, the latest phase of the project gets underway, which will put greater emphasis on breeding for durable resistance to yellow rust and brown rust in winter wheat.

The monitoring relies on samples of diseased leaves from diverse wheat varieties and regions to build a picture of the distribution of rust pathogens and the impact on varietal resistance.

Last year, the weather was conducive to brown rust, while yellow rust was much less prevalent than in recent years.

Although no major changes to the wheat yellow rust or wheat brown rust populations were detected in the latest UKCPVS screens, the situation can change rapidly.

However, remember that mild and wet winters are conducive to rusts and early disease pressure is not necessarily a sign of a shift in the pathogen population.

If you are concerned, then send in a sample to UKCPVS for testing (it is easy and free).

Simply complete a sampling sheet (available via ahdb.org.uk/ukcpvs), pop it in a paper envelope with the leaf sample and send it (as soon as possible) to FREEPOST UKCPVS.

Yellow rust on young wheat plants at an RL trial site in Spalding, Lincolnshire (early March 2025).