Plant pedigrees help battle against wheat disease

Keeping disease at bay often seems like an uphill battle – but one leading seed breeder believes it could be made easier if growers had better information about plant pedigrees when deciding which varieties to drill.

A narrowing of the genetic base means some farmers could unwittingly be growing a range of wheats susceptible to the same disease, says international seed consultant Bill Angus. That’s because some wheats share the same parents – despite being different varieties.

“We are starting to see more and more breakdowns of varieties,” Mr Angus explains. “Why are we seeing that? Because breeders are basically all dipping in the same pond. They are all chasing the same set of genetics.”

As an example, he cites the drive to develop new varieties with resistance to wheat orange blossom midge. This saw Robigus become one of the most widely used parents when it came to developing new varieties.

“Robigus was a great variety but there was a big pressure to deliver more and more orange blossom midge resistant varieties. Breeders used it as a recurrent parent, which resulted in a narrowing of the genetic base – with basically everyone piling in.”

Robigus, for example, morphed into Oakley, which morphed into KWS Santiago, which morphed into KWS Kielder, says Mr Angus. “It is very simple. If you chase the pedigrees back, you’ll see that they all come from the same source.”

When Robigus went down with yellow rust, Mr Angus says it was little surprise that Oakley followed a few years later, followed by KWS Santiago and KWS Kielder. “That is just one example – and it isn’t knocking KWS who have done a fantastic job developing that germ plasm base.”

Helping to address the relatively narrow genetic base of resistance in UK wheat varieties is one of the goals of the Agrii National Cereal Disease Survey, which aims to bridge the knowledge gap for UK growers, agronomists and breeders (see A vital role in variety selection, below).

Growers should know the pedigrees of the varieties they drill so they can assess the risks associated with growing them, says Mr Angus. “One of the things that has been removed from the Recommended List is pedigrees. If you go back 20 years or so, you’ll find the pedigrees in there.”

Only 5-10% of growers know the parents or the grandparents of the varieties they choose, he adds. Yet most growers are well aware of the active ingredients of the agrichemicals they purchase – and the same approach should be taken when selecting seed.

“Growers need to know when they are growing a variety, what they have in their fields. And at the moment they are increasingly ignorant. It is quite frightening really. And yet it is important that growers know.”

Some farmers think they are growing different varieties because they are from different breeders. But that is not always the case. The varieties Goldengun, Horatio and KWS Rowan were all from three different breeders but all shared the same parents (see box).

“This is happening all the time as people use the same set of genetic material. And it is why digging deeper gives an insight into where the risks are and we can inform growers where the risks are so they can broaden their genetic base.”

Lower grain prices make it increasingly important growers need to reassess their risks – especially when it comes to diseases such as yellow rust, adds Mr Angus. “Using a wide range of varieties with known different resistance factors will help reduce exposure to risk,” he concludes.

A vital role in variety selection

The Agrii National Cereal Disease Survey extends a national monitoring service which tracks changes in the virulence of cereal rust and mildew populations – a tool which plays a vital role in maintaining and improving disease resistance as well as variety selection.

It was established by Agrii after the company identified a need for better disease management strategies in the face of the relatively narrow genetic base of resistance in UK wheat varieties, increasing pressures on agrichemicals and more variable growing seasons.

The 2014 survey involves yellow and brown rust monitoring on untreated tussock plots of 36b wheat varieties grown at 14 locations across the UK. Septoria tritici levels are also being monitored in untreated plots across a sub-sample of sites and varieties.

Disease levels are scored regularly throughout the season to provide “up-to-the-minute” early warnings of disease development by varieties in each area so Agrii agronomists can ensure the most timely and cost-effective treatment.

Varieties with the same pedigree

Goldengun (RAGT) = Alchemy x Oakley

Horatio (Limagrain) = Alchemy x Oakley

KWS Rowan (KWS) = Alchemy x Oakley


Monterey (JB Agriculture) = Istabraq x Robigus

Leeds (KWS) = Istabraq x Robigus

Twister (KWS) = Istabraq x Robigus

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