Relevance of verticillium wilt (Verticillium longisporum) in winter oilseed rape in the UK

Summary

Sector:
Cereals & Oilseeds
Project code:
RR72
Date:
01 March 2008 - 28 February 2009
Funders:
AHDB Cereals & Oilseeds.
AHDB sector cost:
£15,950 from HGCA (Project No. 3413).
Project leader:
P Gladders ADAS Boxworth, Boxworth, Cambridge CB23 4NN

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About this project

Abstract

This review was commissioned in response to the first confirmed cases of verticillium wilt in oilseed rape in the UK in 2007.  The fungal pathogen involved, Verticillium longisporum, has been characterised by molecular and conventional methods and is distinct from the two common wilt pathogens V. dahliae and V. albo-atrum. It has larger spores, a greater DNA content in the nucleus and high specificity for Brassica species compared with V. dahliae.  It is an important disease in oilseed rape in other European countries, particularly Sweden and Germany, and also affects vegetable crops in USA and Japan.

The disease cycle involves soil-borne microsclerotia that germinate to produce hyphae that invade root epidermal cells and progress across the root cortex and colonise the vascular tissue (xylem).  The fungus spreads up the plant in the xylem in the spring, but symptoms only appear in the crop near maturity when numerous black microsclerotia are produced outside the vascular tissue. Symptoms cause premature ripening with yield losses up to 50% in Europe, though damage is affected by weather and varies from year to year.  Verticillium wilt appears to be established and caused some crop loss in southern and central England. Its incidence ranged from 1-90% plants affected in fields monitored in 2007 and 2008.

There are some differences in susceptibility to verticillium wilt between winter oilseed rape cultivars, but levels of resistance in oilseed rape are limited and insufficient to prevent damaging attacks. New sources of resistance have identified in various other Brassica species, which, with further breeding work, could produce oilseed varieties with acceptable levels of resistance in future. There are no fungicide treatments available at present. Microsclerotia are thought to be capable of long term survival in soil (10-15 years), but the number of viable microsclerotia is likely to decline with time. Longer rotations with at least three years between brassica crops appear to be the most practical control strategy at present.

Priority should be given to: (i) establishing the occurrence of V. longisporum in oilseed rape in UK, (ii) developing soil tests to quantify inoculum, (iii) research to assist development of resistant varieties, (iv) identifying the conditions that favour infection and yield loss, and (v) determining the rate of decline in soil between susceptible crops, in order to inform rotation planning.  Increased awareness of this new disease threat is required so that oilseed rape management strategies can be adjusted to safeguard future cropping. 

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