3 days ago
Tillage: Irish wheat crops and the threat of yellow rust
The jury is still out on whether or not wheat crops grown in Ireland this year have succumbed to a yellow rust genetic breakdown, as seems to have been the case in the UK.
According to Teagasc tillage specialist, Shay Phelan: 'The yellow rust issue is being investigated at the present time.
'Whatever the outcome of the work, it seems safe to conclude that the growing of wheat will become a more expensive operation into the future.'
Meanwhile, the Agricultural and Horticultural Development Board (AHDB) in the UK is advising farmers not to rely on the current yellow rust disease resistance information published in the organisation's recommended list (RL) information sheets.
Unusual activity was first seen in late March in an RL fungicide-untreated trial near Sunderland in the north-east of England.
At this site, several varieties had yellow rust symptoms despite being classified as resistant to the disease at the young plant stage on the RL (2025/26).
Paul Gosling, who manages the RL at AHDB, said: 'Following discussions with plant breeders, we suspected that an important yellow rust resistance gene – Yr15 – had potentially been overcome.
'We subsequently observed similar resistance-breakdown patterns more widely in RL trials, starting in southern Scotland before spreading down the eastern coast of England, down as far as East Anglia.'
Trial operators sent diseased leaf samples from the affected RL trial sites near Sunderland and Berwick-upon-Tweed for analysis by the AHDB-funded UK Cereal Pathogen Virulence Survey.
The National Institute of Agricultural Botany (NIAB)-led service confirmed that Yr15 gene had failed.
Pathogen isolates from these samples not only infected a test variety known to carry the Yr15 resistance gene but went on to sporulate profusely.
NIAB-funded work using molecular markers also confirmed the presence of the Yr15 gene in several of the varieties impacted at the young-plant stage.
The initial tests prioritised testing of varieties with a strong level of adult plant stage resistance (disease rating 8 or 9), according to RL 2025/26.
These tests found that the Hard Group 4 varieties KWS Dawsum, LG Typhoon and Champion carry the Yr15 gene.
NIAB is currently testing a wider range of varieties, with further genetic screening also being done by the John Innes Centre in Norwich and the Global Rust Reference Centre in Denmark.
The Yr15 resistance gene, which was discovered in the 1980s, confers broad-spectrum resistance against genetically diverse yellow rust isolates (from a large worldwide collection of more than 3,000) and was an important line of defence.
Gosling added: 'Adult plant resistance has clearly taken a knock, but the full impact will depend on a myriad of other resistance genes, which vary from variety to variety.
'Some varieties appear to be fighting back, whereas others are recording unusually high disease levels.'
'Although we have not seen the unusual symptoms towards the south or the west, it appears to be spreading fast.
'No doubt it will impact on variety choice and disease management across the UK next season.'
