27 November 1999

Yield put at risk

Soil-borne viruses are a growing threat to both wheat and barley. Tom Allen-Stevens reports.

IF YOUR soil is infected with one of the cereal viruses and you dont know about it, you could be losing out twice. Not only will there be perennial yield losses, youll be wasting money on the wrong cures.

According to Mike Carver of Arable Research Centres (ARC), the barley yellow mosaic virus (BaYMV) is often misdiagnosed because the symptoms are very similar to other problems such as transient nitrogen or manganese deficiency, or water-logging.

"Look for parallel, yellow tramlining on the leaves. Its distinctive because its the young, developing leaves that are pale and streaky," says Dr Carver. "The disease is now exceptionally widespread throughout the UK – every barley-growing county has suffered incidences."

First reported in 1980, BaYMV has spread quickly. A second virus, barley mild mosaic virus (BaMMV), has also been identified and there is no known cure for either. However, some varieties are resistant, and this is the only protection.

HGCA-funded research into resistant varieties has been carried out by Dr Carver and his team in collaboration with IACR Rothamsted. They have discovered that the yield variations can be huge: "If you have BMV, you virtually have to rewrite the NIAB Recommended List, because of the variation. While the mean yield does not drop too much, individual varieties can suffer enormously; the spread of yields on our infected trial sites has been much greater than the spread on NIAB plots," says Dr Carver.

ARC is also collaborating with Central Sciences Laboratory to evaluate a rapid field testing kit. The aim is to give a diagnosis in five minutes.

Such rapid diagnostic techniques may prove essential defence tactics against the new soil-borne wheat mosaic virus (SBWMV), which has been confirmed in Wiltshire. There are worrying indications that this virus could spread as rapidly as BaYMV.

An ARC trial has now been set up on the infected farm. There is also an HGCA-funded trial under way, in collaboration with NIAB.

Losses can be severe: up to 40%. Current indications are that Charger has a level of resistance to SBWMV infection.


Variety NIAB 99 ARC ARC

one-year BaYMV BaMMV

results site site

Mean yield (t/ha) 8.07 7.84 7.00

(yield as % of site mean)

Laurel n/a 119 126

Jewel 103 114 115

Intro 99 112 114

Hanna 102 111 90

Vanessa* 101 110 100

Mariner n/a 108 99

Heligan 99 107 91

Siberia 112 107 105

Vertige 99 105 77

Fanfare 100 103 107

Epic 95 103 98

Gleam 103 100 105

Antonia 102 99 101

Angela 107 98 93

Muscat 105 95 111

Flute 96 94 100

Rifle 101 90 100

Halcyon 90 89 87

Pearl 103 82 n/a

Regina 103 78 99

Artist 94 76 90

*some resistance to mild mosaic

Red: Mosaic virus resistant

Source: ARC and NIAB