There's been a major shake-up to Recommended List (RL) wheat rust ratings by AHDB following a new rating system.

The latest online edition of the Recommended Lists for cereals and oilseeds (RL) 2021/22 will feature major changes to rust disease-resistance ratings.

The new rating calculation better reflects the diverse and dynamic nature of the UK’s rust populations, it said, prior to launch on on Monday, November 30. The latest developments will also feature during AHDB’s Agronomy Week – a five-day series of online agronomy webinars and videos – that starts on the same day.

Catherine Harries, who works on the RL disease ratings at AHDB, said: “The yellow rust population structure varies in time and space, right down to variation across a single leaf. With rust pathogen populations continually evolving and disease pressure increasing, we have recently encouraged closer crop inspections. This is the best way to assess in-season pressures.

"However, it has become clear that we need to overhaul the rating’s process, in response to the new reality of tremendous rust diversity.”

During 2020, the RL board consulted with agronomists, farmers, pathologists, wheat breeders and statisticians, to develop a more representative method to calculate brown and yellow rust ratings.

To complement the adult-stage yellow rust resistance ratings published in the RL, the UK Cereal Pathogen Virulence Survey (UKCPVS) determines young-plant resistance to yellow rust for recommended and candidate varieties in RL trials. The latest results show no change in resistance in 2020, compared with 2019 – most remain susceptible.

However, a high number of candidates are resistant at the young-plant stage.