New HGCA rust ratings likely to change in season
Rust resistance ratings on the new HGCA Recommended List are liable to change once varietal testing of new races is completed.
The new races detected last season did not necessarily infect Recommended List trial plots, leaving HGCA unable to fully update its ratings.
Instead the resistance scores should be treated as a holding position, and growers should read carefully the footnotes on the List for the varieties most likely to be affected.
Laboratory testing of isolates collected from the new yellow rust race is over half way through, says Rosemary Bayles, principal cereal pathologist at NIAB TAG. The new yellow rust race, which is virulent on Warrior, infects varieties already affected by the Solstice race, as well as some others, she says. Further testing in inoculated field trials will complete the picture in the spring.
Simon Oxley, HGCA’s Recommended List manager, says the HGCA will be working closely with NIAB TAG to explain rust developments and get timely information out to growers. “At the moment, we can only give growers a warning.”
Warrior’s yellow rust score on the new list published on the HGCA website last week is an eight, having only dropped by one point. “That’s likely to fall further,” says Dr Bayles.
Newly recommended Group 3 winter wheat, Torch, which has joined the new list with a rating of four, will also be tested. “It was highly susceptible at some sites last year, but escaped infection altogether at others. It’s another score that will change.”
Torch differs from Warrior, however, as it has always shown some susceptibility to yellow rust, she adds. “It was never going to have a nine. But we need to understand which races are attacking it.”
Her message to growers is to be vigilant. “One more season is needed before we can be any clearer, although information will be made available as soon as possible. If yellow rust is a major concern, go for one of the safer varieties.”
Lee Bennett, of Openfield, believes growers need to know which yellow rust race is infecting Torch, so they can work out how to manage the variety.
“At the moment, it’s an unknown. The rating may well tumble, which has implications for any variety you want to grow alongside it.”
He also predicts the yellow rust ratings for other varieties will drop. “There are some very flattering scores out there. The sooner we know more about this race, the better. Then we can use the Diversification Group information.”
Barry Barker of Masstock suggests that Torch is in some ways similar to Oakley. “Even if the rating drops it will be no worse than Oakley which still has a significant market share.”
“Oakley was removed from the list because of poor yellow rust resistance and Torch was hit by yellow rust at some sites last year and we would advise growers of both varieties to treat the seed with a fluquinconazole based seed treatment.”
Brown rust
Hard Group 4 feed Stigg still has a nine rating for brown rust, despite succumbing to a new race last season. As with the yellow rust ratings, further testing will determine what its new rating should be, and which other varieties the “Stigg” race of brown rust infects.