Updated: Jan 21, 2021
AHDB has changed the way yellow rust ratings for winter wheat are calculated to enable growers to better differentiate between individual varieties’ resistance to the disease.
Several leading wheats have had their scores reduced on the 2021/22 Recommended List as a result. This does not mean that these varieties have become more susceptible since last year, it simply means that the same amount of disease has resulted in a lower rating on the 2021/22 RL compared to the previous list.
Under the new system, the lowest yellow rust rating has been reset to a 3, as was the case in 2012, rather than the 5 on last year’s list. This is partly brought about by a shift in yellow rust populations in the intervening years.
This means the range now runs from 3 to 9. These extremities are used as fixed points for a sloping line that the AHDB uses to convert yellow rust disease levels into a rating. The change has stretched and steepened that line, teasing out differences between varieties that will help growers make more informed choices.
As a result, the yellow rust rating of RGT Skyfall, one of the most widely grown wheat varieties in the UK, has dropped from a 5 to a 3. Catherine Harries, who works on disease ratings at AHDB, says:
“Even on varieties with a 3, sufficient yellow rust control can still be achieved with a combination of chemical and cultural control, so please don’t discount them."
“It is also good to vary varieties with different ratings to reduce the likelihood of breakdown in the future.”
David Schafer, RAGT Seeds UK wheat breeder, welcomed a change. “Breeding companies were in agreement that something needed to be done to better differentiate varieties’ yellow rust ratings.”
In terms of RGT Skyfall, he said: “Three is the new five – its relative resistance has remained largely unchanged over the past three seasons, whereas other varieties have seen great movement.
“We had a high pressure year last season, so those who managed to grow it successfully should expect similar performance."
“High yields, excellent quality and good functionality make it a favourite among UK milling wheat growers and end users. It is the only Group 1 winter wheat with OWBM resistance and also has the best fusarium and brown rust scores in that group. It is also very easy to harvest –nothing else seems to flow through the combine like it.
“It remains a very consistent variety – let’s not forget it took the top spot in Agrii’s wheat sustainability index this year.”