AN UPRISING of new types of yellow rusts in winter wheat crops, has led to a fresh naming system for races now being discovered in the UK.
A new race, announced by the UK Cereal Pathogen Virulence Survey (UKCPVS) in 2016, has been named ‘WYR Blue 7’ under the new system – replacing its provisional name of Invicta.
This is just one of several yellow rust population changes which also led to a radical revision of disease ratings in the AHDB Recommended List (RL) last autumn, where some varieties were downgraded due to susceptibility.
The new naming system was unveiled at the annual UKCPVS stakeholder event, in Cambridgeshire, where Dr Sarah Holdgate, its project manager at NIAB, said: “Last year was far from straightforward, from a yellow rust perspective. By mid-March, 2016, we had received a record number of infected samples from wheat crops. It was a sign that something big was happening and the season ended with major revisions to RL ratings.
“Although we are still looking to pin down the race or races responsible for the breakdown, our monitoring has detected new races in the UK population and we are keeping an eye on them.”
The arrival of the Kranich race and a second new race was announced by the UKCPVS in 2016. Invicta – now WYR Blue 7 – appeared similar to old UK isolates (such as the Solstice race), based on its ability to cause disease. 
Subsequent genotyping, however, showed that the race appeared more similar to the Warrior population.
Dr Holdgate continued: “Until now, naming a race based on the variety on which it was first detected has served us well. But this no longer copes with the complex genotypic and pathology data we are seeing and we feel it is important to avoid using a variety’s name.”
A complete set of findings, based on 2016 isolate testing, was also presented at the event. For wheat yellow rust, the Warrior race continued to dominate samples, with the Warrior 4 group found in at least half of samples tested by UKCPVS and, after a period of decline, Warrior 1 increased in frequency in 2016. 
Virulence frequencies for most genes remained relatively stable in 2016. However, the YR7 gene was more prevalent, as was the YR8 gene (which is an indicator of the Kranich race), although it remained relatively rare.
For wheat brown rust, disease levels were relatively high in 2016 but no unexpected disease was reported to UKCPVS, though relatively high levels were found again in Crusoe.
For wheat and barley, powdery mildew’s virulence frequencies remain broadly similar to those seen in recent years.
Due to the diversity in UK pathogen populations, people are being asked to monitor crops closely and to report unexpected findings to the UKCPVS. If you would like to get involved in the survey, sampling instructions are available from