The presence of a further ‘significant’ wheat yellow rust race in the UK has been confirmed by the UK Cereal Pathogen Virulence Survey (UKCPVS).

Using a new system, the race has been named Red 24. It joins a second new race, called Blue 7, announced by the UKCPVS in March.

Both races were present in the UK pathogen population in 2016 and tests suggest both races contributed to the major revision of AHDB Recommended List (RL) disease ratings last year.

Yellow rust has been much more stable in 2017 and no significant shifts in associated disease ratings are anticipated in the RL 2018/19 (due for publication on 4 December 2017).

Dr Sarah Holdgate, UKCPVS project manager based at NIAB, said: “Our tests reveal many varieties are affected by Red 24 and Blue 7, so these races are significant.

“As we also know some varieties are more susceptible to one race over the other, it could explain some of the regional disease variation seen in commercial crops recently.

 “The diversity in the pathogen population is captured more effectively by the new naming system and it allows us to separate out the individual races more easily.

“We’ll name each race as we find it and continue to raise awareness of those which are agronomically important, such as Red 24 and Blue 7.”

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Images courtesy NIAB: UKCPVS wheat seedling testing for yellow rust (left) and NIAB Cereal Pathologist Sarah Holdgate (right) 

Seedling resistance status

Updated seedling susceptibility information has also been published online. In 2016, many varieties became susceptible at the seedling stage. The situation, however, stabilised in 2017 and no change in seedling resistance was recorded.

Catherine Garman, who manages disease research at AHDB, said: “As all Candidate varieties in trial have been classified as susceptible at the seedling stage, it leaves only three Recommended varieties with seedling-stage resistance. These are Costello, KWS Crispin and KWS Siskin.”

Although yellow rust was more stable in 2017, people are reminded the situation can change rapidly within a season and crops should be monitored and unexpected findings reported to the UKCPVS.

The UKCPVS 2017 Annual Report includes full details of the monitored changes to the UK cereal pathogen population. The report and seedling susceptibility information can be accessed, in the report archive, via cereals.ahdb.org.uk/ukcpvs