to rise again
By Charles Abel
SPRING barley is due for a renaissance, thanks to better barley yellow dwarf virus control, claims a leading breeder.
"If the crop can produce consistent, reliable yields, it has a place on many farms, particularly with prices at £150/t," comments Mike Collins, director of New Farm Crops.
He blames the disease for the crops crash in 1986/87 and its continuing lack of appeal.
Varieties now available remove that threat, offering more reliable output with malting quality, he says. However, with three consecutive years of low BYDV pressure interest has not been great, he admits.
This year could be different. Analysis of data suggests February temperatures influence the severity of BYDV. This February was warm, with maximum temperatures averaging well above the 7C threshold. Disease levels and yield loss are expected to be high. "We expect a bad year, if not worse than the last bad year in 1990," says NFC barley breeder, Paul Bury.
Applying the NFC theory to weather data from the past 60 years shows BYDV is a problem more often than farmers think. "It seems to reach epidemic levels one year in seven, which farmers see, but it could also be a problem one year in three, which is less widely noticed," says Charles Tasker, trials officer with the company.
Yield trends strengthen the link, NIAB data showing the output from control varieties in recommended list trials dipping from about 6.5t/ha to nearer 5.5t/ha in the bad BYDV years of 1988, 89, 90 and 92, adds Mr Tasker.
The performance of individual varieties, emphasises the BYDV link. At low yielding sites, the tolerant varieties Tyne and Chad did 20-30% better than susceptible varieties.
Newer lines offer an even greater yield differential. Official trials in 1990 showed Chad 20% higher yielding than other varieties, but newcomer Amber 45% better still.
Work by NIAB in 1992 showed Amber carried significantly less BYDV in late June and early July – 3-6% compared with 20-30% infection for other varieties in the trial.
The disease is still underestimated, adds Mr Collins. Not only can leaf yellowing, stunting and reduced tillering be attributed to other causes, such as a nitrogen shortage, but yield can be lost even if symptoms dont show.
NFC claims its BYDV tolerant varieties are unique in Europe. Their discovery was an "unwitting" feature of a breeding strategy which selected lines with the most green leaf area.
Chad was the first to show the effect and now Cooper, Brewster, Cork and Optic all offer the "security of BYDV tolerance, high yield and quality," comments Mr Collins.
The company hopes NIAB will place greater emphasis on BYDV resistance in future recommended lists and is hoping CSL and Rothamsted will investigate the mechanisms behind the observed resistance.
• BYDV tolerant winter barleys are "coming soon, within several years," adds Mr Collins. But the resistance is multi-gene so transferring it to wheat will not be easy, he adds.