Is wheat yellow rust stabilising after the Yr15 breakdown?

A major change in the wheat yellow rust pathogen population led to big revisions to disease ratings in 2025. One year on, Tom Ashfield looks for ripple effects in our harvest 2026 trials and commercial crops.

Last year, a significant new yellow rust strain swept across many major UK wheat production areas.

The strain defeated an important yellow rust gene, called Yr15, that was, and is, present in many UK winter wheat varieties.

We first saw unusual activity in late March in a fungicide-untreated trial in north-east England before resistance-breakdown patterns spread more widely, starting in southern Scotland, then spreading down the eastern coast of England, as far as East Anglia.

The impact was so large that we couldn’t use data from previous seasons to calculate the yellow rust ratings in the current edition of the Recommended Lists for cereals and oilseeds (RL).

Normally, we use data from three years, but disease data gathered before 2025 was deemed no longer representative of the UK’s yellow rust population.

This year, yellow rust has been prevalent again.

However, the pattern has been more predictable, with activity generally highest on varieties with low yellow rust ratings.

Well-timed sprays with rust-active products have largely kept it under control.

In RL trial inspections, yellow rust observations have generally aligned fairly well with the current RL disease ratings for most varieties.

The areas most impacted by the Yr15 strain last year also have many RL trial sites.

This helped tune the ratings to the new strain, making them a relatively good fit with the current rust population.

This year, we’ve observed yellow rust on the most susceptible Yr15 varieties as far west as Devon and Cornwall, so the new strain appears to be spreading widely.

This may sound like a bad thing, but a population with nationwide distribution of the Yr15-breaking strain may be more predictable than one with major geographic differences.

Of course, the Yr15-breaking strain is not alone and is unlikely to have completely displaced other strains.

As the population settles, we may see further adjustments to disease ratings this year, but not at the scale seen in 2025.

The current edition still features several highly resistant varieties wotj disease ratings of 8 or 9.

With many promising candidate varieties in trial, we should see options for yellow rust management increase.

The picture will be clearer when updated ratings are released later in the year.

The next RL edition (2027/28) is due online on 30 November 2026.

Looking even further forward, there is a fascinating new project that aims to unlock novel yellow rust resistance sources in ancient landraces.

The landraces are the result of farmers selecting what grew well long before modern plant breeding.

About one hundred years ago, Arthur Ernest Watkins collected over a thousand such landraces from 32 countries.

Following a century of storage and preservation, most are still in the Germplasm Resource Unit at the John Innes Centre (JIC).

It is phenotypically diverse resource that includes 33 lines with resistance to yellow rust, including an impressive 32 lines that resist the Yr15-breaking strain.

A new Rapid Response grant, from UK Research and Innovation (UKRI) and Defra, is funding JIC-led work to get novel resistance sources from this collection into the wheat breeding pipeline.

The team behind the AHDB-funded UK Cereal Pathogen Virulence Survey (UKCPVS) at Niab is involved in the work, specifically to provide wheat disease monitoring expertise and rapid screening of plant lines.

Wheat brown rust tends to develop later in the summer than yellow rust.

Following conducive weather, we’ve recently seen the disease pick up at RL trial sites, especially on susceptible varieties, with disease ratings of 3 or 4.