Last year was busy for yellow rust. The UK Cereal Pathogen Virulence Survey (UKCPVS), which monitors changes in virulence of cereal pathogen populations, received double the number of yellow rust samples in April than it did the previous year.
More than 300 samples from 88 varieties in 25 counties were received in total, with most coming from the East.
Testing of the samples found 2020 wheat yellow rust virulence frequencies continued patterns of previous years and the yellow rust population continues to show high levels of diversity.
NIAB plant pathologist Amelia Hubbard told the UKCPVS stakeholder event:
“It was [yellow rust isolate] YR8 which we were particularly interested in looking at because that did rise to 17% in 2019, but in 2020 it dropped back down to
Some new pathotypes were found, but at very low frequencies, Miss Hubbard said.
“These came from Lincolnshire, Cambridgeshire, Hampshire, Oxfordshire and North Yorkshire, which really shows there is no pattern to where new pathotypes are springing up in the UK.”
In yellow rust adult resistance trials carried out by UKCPVS last year, in which varieties are inoculated with the disease, five isolates displaying novel pathotypes were investigated.
The most susceptible Recommended List (RL) variety was Skyfall, but KWS Zyatt saw the highest plot infection score of 39.8%, with the isolate 19/215, Miss Hubbard said.
Some RL varieties reacted to just one of five of the isolates tested including KWS Extase and Crusoe with 19/215.
All five isolates infected KWS Firefly in adult plant trials, in particular isolate 19/215, and may help to explain outbreaks on KWS Firefly reported during the
2020 season, Miss Hubbard added.
During tests for seedling resistance, Costello, KWS Siskin and Theodore showed resistance to all five isolates at seedling stage and Crusoe and KWS Extase were susceptible to just one isolate.
“KWS Zyatt was susceptible to all five isolates at seedling stage,” said Miss Hubbard.
Of the varieties on the AHDB Recommended and Candidate Lists, 18 varieties were resistant to all five isolates and nine were susceptible to all five.