Yellow rust (Puccinia striiformis) samples collected from three farm crops of Warrior winter wheat earlier this summer have re-infected the variety in the first round of testing by the UKCPVS at NIAB TAG. 

"Warrior had previously been resistant to all yellow rust disease isolates at seedling and adult plant stages.  The new isolates have now been shown to infect the seedlings of the variety, which is evidence that we are dealing with a new race," explains Dr Rosemary Bayles, principal cereal pathologist at NIAB TAG.

Warrior currently has a rating of 9 for both yellow rust and brown rust resistance on the HGCA 2011/12 Recommended List.

The variety has also been shown to be susceptible to the new race of brown rust (Puccinia triticina) recently identified on the winter wheat variety Stigg.  Tests by UKCPVS demonstrated that a brown rust isolate collected from a field plot of Stigg was able to infect Warrior, while another isolate collected from a plot of Warrior infected Stigg.  "This verifies the presence of a new brown rust race able to overcome the resistance of both varieties," says Dr Bayles.

Initial testing has so far focused on varieties that were considered to have the highest disease resistance rating.  The next step will be to discover which other winter wheat varieties may be vulnerable to the new races of yellow rust and/or brown rust, including field tests next season.