Last year was more of a septoria year than a yellow rust year for winter wheat but what could 2024 bring?
According to the UK’s Agriculture and Horticulture Development Board (AHDB) winter wheat yellow and brown rust pathogen populations can be dynamic, diverse and difficult to keep track of.
The AHDB has highlighted that the latest UK Cereal Pathogen Virulence Survey (UKCPVS) – which monitors cereal rusts and mildews in the UK.
UKCPVS screens rust isolates on Recommended Lists (RL) winter wheat varieties. The work builds an understanding of population shifts and the potential ramifications to varietal disease resistance.
The survey confirms that 2023 was more of a septoria year. This was reflected in the number of yellow rust samples received by UKCPVS: just 92. The most sampled variety was KWS Extase.
Within this relatively small pool of samples, three new pathotypes were discovered, based on their ability to cause disease in a test set of varieties.
In addition, the five most interesting isolates collected in 2022 were tested against adult wheat plants in 2023.
Yellow rust
For the top five widely grown varieties, the percentage of plant infection with yellow rust was generally in line with RL 2024/25 disease ratings.
These were as follows: KWS Dawsum (9), KWS Extase (7), Champion (8), Skyfall (3) and Crusoe (8)
However, KWS Extase showed relatively high levels of infection. Significantly, Skyfall was relatively susceptible to all five isolates, which would not have been unexpected for a variety with a disease rating of 3.
In addition, the latest screening results at the young plant stage detected susceptibility to yellow rust in three varieties listed as resistant at this stage in the current RL (2024/25). These re: RGT Bairstow, RGT Rashid and KWS Zealum.
UKCPVS also examines the genetic patterns in the yellow rust population, which are classified using colours.
The UK yellow rust population is dominated by the red group, with occasional appearances from the pink and purple groups.
And, in this regard, 2023 was no different and this situation is mirrored in Europe.
Where brown rust in wheat is concerned, UKCPVS received 15 samples in 2023 with five new disease pathotypes identified.
Over recent years, a sharp increase in the ability of pathogens to overcome the brown rust resistance gene Lr24 has been identified.
The UKCPVS survey for 2023 confirms that 40% of isolates tested could unlock this resistance gene.
In adult plant tests, no varieties were completely resistant to any of the isolates. However, KWS Dawsum, LG Astronomer and Skyfall all had less than 5% brown rust.