The Agricultural and Horticultural Development Board (AHDB) has carried out a ‘root and branch’ review of yellow rust resistance ratings for wheat varieties featured within recommended lists (RLs).
The end result has been some very large falls in recorded values for some widely grown wheat options.
In addition, the RL yellow rust disease resistance ratings have been published earlier than usual. This is to facilitate the adaptation of management strategies for harvest 2026.
All of this follows the unexpected appearance of yellow rust in some varieties in RL trials in early spring.
As a consequence, AHDB advised farmers not to rely on the RL 2025/26 yellow rust ratings when setting fungicide programmes.
Disease ratings
RL adult plant disease resistance ratings use a numerical scale: from 1 (least resistant) to 9 (most resistant).
Usually, disease ratings for rusts (yellow and brown) are based on data from three trial years.
Since RL 2021/22, the data has been weighted to give more recent data a greater influence on the ratings, making them more sensitive to changes in the rust population.
Because of the sudden widespread emergence of the new yellow rust strain, its specific ratings have been limited to harvest 2025 data that best represent the current situation.
This follows a rigorous validation process.
Yr15 gene
At the heart of the yellow rust flare up has been the breakdown of a specific Yr15 gene, which may feature in about a third of RL wheat varieties.
A dozen varieties have seen ratings fall by two to five points in the new RL data release.
Some other varieties believed to contain the Yr15 gene carry other effective yellow rust resistance genes and have recorded relatively little change in their ratings.
Varieties that do not carry Yr15 are unaffected directly by this new virulence. As a result, about half of the winter wheat varieties on RL 2025/26 have the same disease resistance rating or a fall of one rating point.
Some varieties even recorded a small rating increase, due to declines in the yellow rust strains that they are susceptible to.
Significantly, several candidate varieties are susceptible to this new yellow rust strain, which will impact their chances of being recommended for inclusion on the winter wheat list later this year.
However, some varieties performed relatively well, including some with a yellow rust disease resistance rating of 8.
