In 2017 Emily Addicott-Sauvao, her father, Gerald Addicott, and their agronomist, Stephen Harrison of South West Agronomy, noticed yellow blotches appearing in winter barley on the family farm in Somerset.
The problem became worse as the season progressed, but despite the variety’s BMYV resistance, it still seemed related to the issue which had proved to be the farm’s biggest challenge in growing winter barley, Emily explains.
“We were puzzled about the true cause of the yellowing because we had specifically chosen a resistant variety and no-one else in this area had BYMV.
“We knew that the virus is spread by a root infecting fungus and dispersed by moving the soil, but we do all the field work ourselves using our own machinery and no contractors come onto the farm.
“So it was a real mystery where it had come from. One reason we thought might be a factor were the extremes of weather in recent years, with very wet, followed by very dry conditions.
“Perhaps the plants were under greater stress and more susceptible to infection? At that stage we did not know and were speculating as to the cause.”
The very wet winter of 2019/2020 was followed by good growing conditions from February onwards, she recalls
“The two-row feed variety we had grown for several years and had Type 1 BYMV resistance, looked great early in the season but then yellow patches became apparent, so we sent leaf samples for laboratory analysis.
“Nothing was found and the crop appeared to grow out of the problem, but clearly the virus must have affected its development and ultimately yield, so we had to find an alternative.
“Stephen put a lot of effort into discovering that the cause of the yellowing was the rare Type 2 BYMV.
“That made us wonder just how prevalent it is in the UK, because most varieties which claim BYMV resistance are only Type 1 resistant.”
A TRICKY PROBLEM TO IDENTIFY
It took a while to identify the problem at Corston Fields Farm, Stephen confirms.
“Over several years we had seen various areas of winter barley exhibit poor growth and underperform but thought this might be related to the fact that the previous tenant had grown barley continuously.
“Even though that was before Gerald took on the tenancy in 1984 and over 30 years had elapsed since, BYMV is soil-borne and can carry over for a long time.
“Historically, the two-row variety which we were growing had always done well on this farm, but the increasing amount of yellowing in the crop which we noticed four years ago was concerning.
“I asked several other people to look at it, but none could pinpoint exactly what it was.
“Type 2 BYMV will often be confused with other things such as manganese deficiency but given the effort that goes into the management of crops at Corston Fields Farm I knew that it had to be something more than a mineral or nutrient deficiency.”
On 2017 Stephen sent a leaf sample to the Food and Environment Research Agency (FERA) for visual appraisal, and they replied it was almost certain to be Type 2 BYMV.
“It is a nightmare where present, so I had them carry out a full tissue analysis, which confirmed their initial diagnosis,” he explains.
“Because Type 1 BYMV is effectively masked by the resistance all modern barley varieties have to it, a whole generation of younger farmers and managers have never seen the disease.
“If growers have areas of barley where problems keep arising, but these do not respond to normal treatments then, based on our experience, it would probably be worthwhile having a sample analysed specifically to determine whether Type 2 BYMV is present.
“That was a factor at Corston Fields Farm, so I identified a variety which I thought would provide a solution. In 2019, we drilled a field with a Type 2-resistant variety which performed well.
“There was a 1t/ha yield difference between it and the farm’s usual two-row winter barley, so there was no question that BYMV was having a significant detrimental effect on yield and that this was indeed the soil-borne virus we were dealing with.
“That variety never became available commercially, so we had to find an alternative for autumn 2020 sowing and identified DSV Sensation.
“Because it is relatively tall and would need careful management, I discussed it at length with Emily and Gerald, who does most of the spraying, but we all agreed that this would be the best way forward.
“Sensation is totally different to the farm’s previous two-row winter barley in terms of growth habit,” Stephen explains.
“It gets away early, grows rapidly all of the time and establishes a strong root structure, but because it is taller requires more intensive management in terms of PGRs and application timings.”
FULLY BYMV RESISTANT
“We were fortunate to secure some of the limited seed that was available,” Emily states.
“This is the first time that we have grown a six-row barley and as we are on quite Brashy ground my initial question was could we achieve a high enough bushel weight?
“From what I have seen that will not be an issue because the breeder’s data states that it is extremely high yielding, with good straw strength and very high specific weight.”
According to Sarah Hawthorne of DSV, Sensation is a top yielding, early maturing 6-row winter barley with high levels of tolerance to Barley Yellow Dwarf Virus (BYDV) and resistance to both strains of BYMV.
“Research by our breeders highlighted that the yield difference between varieties which are resistant to both types of BYMV and those which are only BYMV 1 resistant can be 10% to 40% in fields where BYMV 2 is present.
“Therefore, by knowing which strain is present and selecting the right variety growers can greatly improve the yield.
“part from its tolerance to BYDV and resistance to both types of BYMV, DSV Sensation is a strong performer with a good disease resistance package, she adds.
“As well as a high specific weight, it also has outstanding spring vigour making it one of a the most competitive varieties against blackgrass currently available.
“Sensation has also demonstrated an ability to head up to five days earlier than other popular BYDV varieties – 128 days compared to 133 – as well as being suitable for early sowing dates.”