Two top-selling feed wheat varieties – Reflection and Diego – look to be the big losers in the sharp downgrading of their resistance rating to yellow rust disease.

The two were the leading feed wheat varieties for harvest 2016, but their susceptibility to yellow rust means their popularity is slipping sharply.

See also: Wheat varieties get sharp downgrade in yellow rust rating

Many wheat growers saw that these two were becoming more susceptible to the yield-robbing yellow rust earlier this year, and this has been confirmed by the AHDB as new races of the disease have emerged.

Reflection’s rating for yellow rust resistance slips to a 3 from a 6, and Diego to a 5 from a 7, in a 1-9 scale where 9 is good resistance and 1 is very poor.

Market share falls

Reflection’s share of the certified seed market has dropped to about 1.5% this autumn from 10% in autumn 2015, and could fall further, while Diego has declined to about 7% from 13%.

Barry Barker, national arable seed product manager at distributor Agrii, expects both varieties to show further declines, but growers are likely to be kinder to Diego as they have known the variety for longer.

“Reflection will decline as growers focus more on the growing costs of different varieties rather than out and out yield,” Mr Barker tells Farmers Weekly.

Reflection was the top yielding winter wheat when it entered the AHDB Recommended Lists in December 2014, but many growers and agronomists saw high levels of yellow rust in the variety last spring.

The AHDB decided to look at just one year’s data from 2016 to assess the disease rating, rather than a three-year average following the confirmation of a new “Kranich” race of yellow rust, while a potential new race – provisionally named Invicta – has also been found.

Big changes 

Simon Oxley, a cereal variety expert who runs the Recommended Lists at the AHDB, says it has been the biggest change in yellow rust ratings since the Warrior race appeared in 2011.

”There was such a big difference this year compared with last year due to the change in races that, in effect, it was like looking at a new disease,” he says.

The rating changes will be incorporated into the new winter wheat Recommended List for 2017/2018 to be published at the end of November.

Varieties drop off the Recommended List if a disease rating drops below 3 or their seed area declines dramatically.

Agrii’s Mr Barker says there are varieties to take some of the market share from Reflection this season, including newcomers Graham and Siskin.

Experts say Diego’s yellow rust rating of 5 will make the variety more manageable, but it is expected to decline slowly as better varieties emerge.

Zulu downgraded

The other big faller among popular wheats is the leading biscuit-making variety Zulu, which fell to a 5 from a 9 for yellow rust resistance. The variety is widely grown, especially in the North, where it is grown for distilling.

Experts point out that newer varieties such as Barrel and Basset could take market share from Zulu and they have higher yellow rust ratings.

Bill Clark, technical director of crop consultant NIAB, welcomed the AHDB move to use just one year of data to make the disease rating changes.

“Growers will be able to look at disease ratings now with much more confidence,” he adds.

Yellow rust disease ratings revisions

Use the table below to search for the wheat varieties you are growing and see how the yellow rust ratings are affected.