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Agricultural research scientists working for the government's 

Agricultural, Development and Advisory Service at Rosemaund in 

Herefordshire have identified a disease of oilseed rape previously 

unknown in the UK. And they believe the disease, verticillium wilt, 

may have been responsible for falling yields of the rape in recent years.



"This is a disease we suspected but now we have confirmed its 

presence in the country," scientist Jonathan Blake told the Hereford 

Times this week. But Mr Blake was quick to point out that it is not 

thought that this verticillium wilt has any link to another 

verticillium wilt, the progressive strain of which has proved fatal 

to hop plants in the county and Kent for many years. Research will 

continue to establish what strain it is. "It is a coincidence that 

they both have the same name," he said. "We believe there is no need 

for farmers to worry if they consider planting oilseed rape on ground 

which previously grew hops."



What effect this newly identified disease will have on the future 

yields of oilseed rape will depend on further research by scientists 

at Rosemaund. But Mr Blake did say that the disease may be weather 

and season related.



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[Verticillium wilt of oilseed rape (_Brassica napus_) is caused by 

the soil-borne vascular fungus _Verticillium longisporum_. This 

species attacks oilseed rape and other brassicas in many European 

countries including France, Germany, Sweden, as well as in Japan. It 

was recently recorded in California infecting cauliflower. The 

growing area of intense rapeseed cultivation has rendered the 

pathogen an increasing threat to oilseed rape production particularly 

in Europe.



Unlike other _Verticillium_ diseases, _V. longisporum_ does not 

induce wilting, but premature senescence and ripening which may 

severely reduce yields by up to 50 percent. It can survive in dead 

plant tissue and soil for extended periods. Disease management 

includes deep ploughing to minimise inoculum and crop rotation with a 

succession of non-susceptible species such as cereals or grass. 

Fungicides are largely ineffective for a soil-borne pathogen. 

Sufficient genetic resistance is not available in oilseed rape making 

resistance breeding almost impossible. Resynthesized rapeseed 

generated from interspecific hybridisation between resistant forms of 

_Brassica rapa_ and _Brassica oleracea_ represents a potentially 

important resource for developing resistant crop lines.



_V. longisporum_ was previously known as _V. dahliae_ var. 

_longisporum_. It has now been established as a separate species, 

although some controversy still remains regarding its classification. 

Its host range is different from the one of _V. dahliae_. A clear 

restriction of _V. dahliae_ to non-Brassica hosts (including 

solanaceous crops such as tomato and eggplant) was observed while _V. 

longisporum_ is pathogenic only on _Brassica_ species. Molecular 

methods have revealed a hybrid nature of the species with components 

of _V. albo-atrum_ and _V. dahliae_ both present in _V. longisporum_. 

Thus _V. longisporum_ appears to be a host-adapted pathogen. This 

explains why a threat to hop crops from the oilseed pathogen is 

considered unlikely in the news report above.



_V. albo-atrum_ (and occasionally also _V. dahliae_) is associated 

with verticillium wilt of hops. It also affects lucerne, hemp, and a 

number of other hosts. In hops, one or all of the trained vines in 

one hill can die off either one after the other or simultaneously. 

Strict hygiene measures are necessary to minimise the likelihood of 

introducing the disease into hop plantings. Some hop varieties with 

disease resistance or tolerance are available.



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2006

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2005

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Verticillium wilt, eggplant - Italy 20050816.2401]

...................................dha/mj/mpp