Wheat varieties under pressure

How is the current wheat variety portfolio coping with this season’s extreme disease pressure? And will the candidate varieties waiting in the wings fare any better?

Those are questions that need answering, believes independent wheat consultant Bill Angus, who predicts that some growers will be disappointed with their final yields.

“It’s certainly an interesting year for disease pressure,” he says. “And it’s come on the heels of some very low disease years, which have had an effect on disease rating standards. They’ve been eroded by a lack of disease capture.”

This means that disease resistance ratings, which would have been a four in a more normal year, have become a six instead. “It’s due to a lack of data, rather than any error,” he explains.

His belief is that minimum disease standards should rise, with the Recommended List setting clear targets against agreed timescales.

“We should aim to have a minimum disease resistance rating of four, with no variety being accepted into the system with a lower score than this, but stipulate that the minimum score rises to five in four year’s time. That would help to stop yield being the deciding factor.”

The same could be done with grain quality parameters, he adds. “There’s no reason why a similar system couldn’t be adopted for specific weight, for example, so that we keep on improving.”

His other concern is that there’s a lack of diversification among current wheat variety choices. “Everything is related to each other and varieties have built up in the market place. So in a season like this, there are bound to be problems.”

The solution is to have a balance of varieties with polygenic resistance, running alongside a drive to raise standards, suggests Mr Angus.

“There are some good examples of varieties which have raised the bar, but there are also too many which don’t offer enough in the way of disease resistance.”

Last year’s Group 1 addition, Crusoe, is one of the former, he notes. “It may not offer more yield than the existing choices, but its disease ratings are much better, especially among the milling types. So it is a step forward, despite the fact that it doesn’t have orange wheat blossom midge resistance.”

He also highlights Relay, a new hard Group 4 variety, as another example of better disease resistance than its counterparts. “It looks good and offers something different in that category.”

Another hard Group 4, JB Diego, also gets a mention. “There are no storms ahead for JB Diego. It’s not one of the high-risk varieties and it’s been around for a while.”

Looking ahead, he points out that there are 16 winter wheat candidates up for recommendation later this year. Of those, 10 offer orange wheat blossom midge resistance, which suggests that they are all Robigus derivatives.

“It means that they could be vulnerable to changes in yellow rust races, so you don’t want to have them all over the farm,” he explains. “A relatively good disease resistance profile at this stage doesn’t mean that it will remain that way.”

His advice to growers is to look at a variety’s pedigree, not its name. “The parentage will give you some insight into any potential problems ahead.”

He picks out feed type Myriad from the candidates as having a different genetic basis and a solid set of disease ratings.

Agronomist Neil Watson of NIAB TAG believes that growers should take a look at untreated plots when considering varieties.

“It tells you what’s likely to give you problems if you get delayed with your spray programme,” he says. “It’s far more useful than looking at varieties that have received a full fungicide programme.”

He adds that early drilled crops are having greater difficulties with septoria this year. “The T3 spray is going to be really needed to keep crops going.”

Jonathan Blake of ADAS agrees: “We haven’t had a season like this for a while and both varieties and fungicides are being severely tested.”

He notes that it’s very difficult to differentiate between wheats with fours, fives and sixes for septoria resistance at the moment. “Septoria has had perfect conditions, with plenty of rainfall and slow leaf emergence in cool temperatures. So growers haven’t been able to treat them any differently.”

Candidate ratings

Of the 16 candidate wheat varieties, just two (Cougar and KWS Yaris) have a seven rating for septoria tritici. The rest all have sixes, except for Chronicle which has a five.

Mildew ratings range from four (KWS Kielder and Leeds) to nine (Havana and Torphins), while all the newcomers have either an eight or nine for yellow rust, except for QI with a three.

Brown rust scores start at three (Torphins and KWS Yaris) and rise to nine (Cougar, Dickens and Revelation), while eyespot ranges from three to eight.

 wheat candidates

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