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Improved control of novel Agrobacterium-induced diseases in hydroponic crops: risk assessment and biological controlt - HH2308SPC

An unusual Agrobacterium radiobacter strain with a Ri-plasmid, originally isolated from English cucumber crops in the 1970’s, has recently caused major problems in rockwool grown cucumbers throughout England. Root mat disease results in increased root vigour but reduced yields and delays in cropping. The disease has also recently been found in rockwool grown tomato crops. So far root mat appears to be endemic in the UK but there has been only one confirmed case elsewhere in Europe. Little is known of the epidemiology of this pathogen or the risks it poses to other crops.

Financial losses incurred by root mat infection are difficult to quantify. Horticultural consultants have estimated that losses in cucumber are in the region of £15, 000 per ha. However due to reduction in fruit size and quality, losses in tomato are even greater at around £36, 000 per ha (in cherry tomatoes). These figures do not include the impact of secondary diseases such as Pythium infection which root mat affected crops are more susceptible to. Research has also shown that the Ri-plasmid can survive in rockwool, even after steam sterilisation, and allow re-infection in subsequent growing seasons. As a result many growers now dispose of rockwool each year rather than retaining it for re-use. Rockwool costs between £4, 500 - £5, 000 per ha to replace and there are other financial and environmental costs in disposing of used rockwool which can only be removed to landfill. Plant propagators in the UK have also suffered losses with some growers now buying plants in the Netherlands in an attempt to avoid root mat infection. The loss of this business to UK propagators has been estimated to be in the region of £600, 000 per annum.

This project aims to study aspects of the epidemiology of the pathogen and, by genetic studies, assess the risks posed by the plasmids which confer pathogenicity. Plasmid deficient Agrobacterium strains are also abundant, especially in hydroponically grown crops, and since these can readily acquire plasmids the risks of disease spread appears to be significant. We also aim to investigate possible biological control methods.
1. To assess the potential for spread of the Ri-plasmid into other micro-organisms.

2. To develop an in vitro root culture screening test for the rapid evaluation of the pathogenicity of Ri-plasmid harbouring bacterial strains and also the potential effectiveness of novel control agents.

3. To assess the variability of the Agrobacterium Ri-plasmid in root mat, and other strains.

4. To isolate bacteriophages, and also identify other novel classes of control agents, capable of controlling or eliminating pathogenic Agrobacterium sp.

5. To monitor the survival of Agrobacterium sp. and the Ri-plasmid.

6. The immediate dissemination of results to the industry and submission of suitable biocontrol agents for approval for commercial use.

Project Documents
• Final Report : Improved control of novel Agrobacterium induced diseases in hydroponic crops through risk assessment and biological control   (779k)
Time-Scale and Cost
From: 2002

To: 2004

Cost: £156,664
Contractor / Funded Organisations
Central Science Laboratory
Biological Control              
Biotech-non GM              
Disease Control              
Protected Cropping              
Sustainable Farming and Food              
Sustainable Production              
Fields of Study