Several wheat varieties have seen their ratings fall in the latest AHDB RL 2026/27 data release, some by up to five points.
Resistance ratings have been published earlier than usual to facilitate the adaptation of management strategies for harvest 2026. Usually, disease ratings for rusts (yellow and brown) are based on data from three trial years. However, because of the sudden widespread emergence of the new yellow rust strain with virulence (ability to cause disease) on Yr15, 2026/27 yellow rust ratings have been limited to harvest 2025 to best represent the current situation.
Some varieties believed to contain the Yr15 gene carry other effective yellow rust resistance genes and have recorded relatively little change in their ratings.
Siobhan Hillman, who leads on the rating calculations at AHDB, said: “This is only the second time we have issued the yellow rust ratings based on a single year; the previous occasion was in 2016, which was also after a significant shift in virulence.
“Genotyping analysis, by NIAB and the John Innes Centre, suggests that the Yr15-breaking strain probably evolved by mutation in late 2024. In the UK, it was first seen in North East England and spread rapidly in the spring, impacting many RL trials and commercial crops. Yr15-virulent isolates have also been identified in several other European countries this year.”
NIAB-funded work suggests that the Yr15 gene may be in about a third of RL varieties.
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 limited to one rating point. Some varieties even recorded a small rating increase, due to declines in the yellow rust strains that they are susceptible to.
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.
