RAGT is introducing the first European winter wheat variety with a high level of resistance to barley yellow dwarf virus.
Cutting-edge genetic science is at the heart of the development of a high yielding feed wheat which is resistant to barley yellow dwarf virus (BYDV).
It is a story that goes back over two decades and has culminated in RAGT bringing RGT Wolverine winter wheat to the UK market.
Dr Chris Burt is the cereal genotyping manager at RAGT and runs its genotyping laboratory which carries out genetic analysis on lines that are going through the breeding programme and looks for traits of interest, including those with resistance to BYDV.
This work enables the laboratory to look at large numbers of lines relatively quickly and efficiently to select those that have the right genetic markers and agronomic characteristics.
The RAGT genotyping laboratory continues to conduct research to identify new genetic markers for a range of disease resistances, such as the Bdv2 gene that confers resistance to BYDV.
Dr Burt says: “The work on the Bdv2 gene is a project that has been ongoing for some 20 years in the UK and was started by my predecessor Peter Jack and the pathologist at the time, Bill Hollins.
“The difficulty they had was they didn’t have a marker they could easily identify, so they were having to look at work in the field to identify resistance.
That limits the numbers you can look at and makes it quite slow.
“Molecular marker technology has improved greatly over the last 10 years.
Initially we had a marker we could use which was low throughput and quite time consuming, but certainly better than looking in the field.
“It’s only in the past three years with the advances in DNA technology that we had a marker we could apply to large numbers of samples and this has enabled us to make huge leaps in the development of new varieties.
“We have a much better understanding of the wheat genome, but we can also process far greater numbers of varieties.
The greater the numbers, the more chance of finding varieties with the characteristics we are seeking – for instance both BYDV resistance and other agronomic benefits.”
Dr Burt is also quick to acknowledge the role played by the whole of the commercial and academic community in the UK.
“The reason we have been able to develop molecular marker tools is because of collaboration across industry and with academics.
It’s something that I think we are very good at in this country,” he says.
“RAGT has put in a lot of work and has been able to use these tools to develop its varieties.” As Dr Burt points out, the work has been a long time in development.
Researchers at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia started work on incorporating BYDV resistance into wheat germplasm some 25 years ago.
They identified the Bdv2 gene in a distant relative of wheat, Thinopyrum intermedium.
This pioneering work in itself was extremely difficult.
Dr Burt says: “The initial work to produce the cross was revolutionary and led to the introduction of resistant varieties in Australia.
This demonstrated you could produce varieties which provided ongoing resistance alongside a good agronomic package. However, these varieties were not appropriate for conditions in the UK.”
While work continued in the UK at Plant Breeding International Cambridge (PBIC) to introduce the resistance into UK varieties, it was not commercialised and the perception was there was little demand for the trait at the time, not least because insecticide seed treatments offered cheap and reliable control.
Richard Summers, head of cereal breeding and research at RAGT Seeds, says: “The CSIRO work did succeed in the commercialisation of BYDV-resistant wheat, one of the very few breeding programmes in the world to have done so to this day.
“CSIRO did this by translocating a genetic segment from Thinopyrum containing Bdv2 onto a wheat chromosome, via a research line known as TC14.
“It is interesting to note the two CSIRO varieties, Mackellar, introduced in 2004, and Manning in 2007, have maintained significantly higher yields compared with BYDV-susceptible varieties when BYDV pressure is high, outperforming all other varieties in this situation.” In 2013 RAGT’s wheat breeding team produced the cross that became RGT Wolverine.
One of the most important aspects of RGT Wolverine’s performance throughout its trials has been its ability to produce high yields competitive with other varieties, as well as providing BYDV resistance.
This has been confirmed in NL trials and extensive trials in the laboratory and in the field.
In the laboratory, RGT Wolverine was compared against a widely grown, fully recommended UK variety as a control.
In addition, two of RAGT’s near identical French lines were tested to provide additional confirmation, one with the Bdv2 trait and one without.
When plants reached the second-leaf stage, BYDV-infected aphids were transferred to each plant.
After 42 days of incubation, leaf tissue samples were sent for ELISA testing to detect virus presence.
The resistant lines consistently showed a significantly lower level of virus compared with the susceptible ones.
Subsequent field trials at Cambridge, Lincolnshire and Yorkshire mirrored the ELISA tests and confirmed the effectiveness of the Bdv2 gene.
Three BYDV strains were confirmed at all three sites by ELISA tests (PAV, MAV and RPV), suggesting the resistance is also broad spectrum.
There will be limited availability of RGT Wolverine this autumn (2020), with the variety launched to the market in earnest in time for autumn 2021.
The ban on neonicotinoids introduced last year had the potential to make a huge impact on the industry and its fight against BYDV.
According to independent consultant Keith Norman about 40 per cent of wheat in the UK is vulnerable to infection following the ban.
He says: “If untreated at present, 82 per cent of the crop area would be at risk with a potential loss of £136 million per year.
Furthermore, the lack of neonicotinoid seed treatments increases selection for pyrethroid resistance.
“There is already resistance in aphid populations and the rise of uncropped areas, the introduction of the new Environmental Management scheme (ELMs) and the increase in maize grown for anaerobic digestion will all add to the increase in aphid populations.”
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