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Epidemiology of viruses of protected crops - HH3212SPC

The purpose of the proposed work is to develop an Integrated Crop Management (ICM) strategy for the control of viruses and the tospovirus vector, western flower thrips (WFT; Frankliniella occidentalis) in protected ornamentals. This work relates to DEFRA`s policy objectives of ensuring that horticultural production is carried out in a sustainable, diverse and adaptable manner, thereby promoting a competitive and integrated produce supply chain which is responsive to the needs of consumers. This will be achieved by ensuring sustainable production of protected ornamentals and preventing virus disease epidemics. Developing robust methods for biological control of WFT vectors would minimise the need for prophylactic pesticide use, which is considered environmentally undesirable, and would also conform to market demand for reduced pesticide use. Many growers of pot and bedding plants currently use biological control methods for WFT within Integrated Pest Management (IPM) programmes but growers of chrysanthemum are still very reliant on regular applications of dichlorvos, which is under threat of withdrawal in the near future. If dichlorvos is withdrawn before reliable alternative control methods for WFT are developed, then growers are likely to experience severe epidemics of WFT. As WFT also transmit the very damaging tospoviruses Tomato spotted wilt virus (TSWV) and the related Impatiens necrotic spot virus (INSV), robust ICM methods for both thrips and viruses must be developed as a matter of urgency. The proposed research will build on results in project HH1758SPC, which investigated the reduction in spread of TSWV in impatiens by biological control of WFT. The research will fill gaps in knowledge of tospovirus epidemiology that are essential for developing successful ICM methods for both vectors and virus in chrysanthemum based on the use of predators and nematodes. The proposal also aims to identify resistance or tolerance in chrysanthemum varieties would would also be a component of the IPM strategy.
The supply of healthy propagation material is also key to integrated management of plant viruses such as TSWV and INSV, and accurate diagnosis of a disease causing agent is an essential prerequisite for effective disease control. Sensitive indexing methods for detection of TSWV in plants and in vitro propagating material have been developed for the industry to implement production of virus-free nuclear stock but there is a demand for greater automation and multiple detection of viruses. DNA chip technology has been used extensively in genomics and medical research and is also now being applied in horticulture. Sequence information generated in this previous project can now be used in the development of microchip DNA technology to rapidly identify the virus group, speed progress and improve the identification of new viruses and would allow detection of all key plant viruses in a single test. This could replace laborious and time consuming virus indexing by ELISA where for a single crop species such as petunia, thousands of plants are currently tested annually by ELISA for at least 26 different viruses. Chrysanthemum is infected by up to 8 different viruses, including TSWV and INSV, plus two viroids, chrysanthemum stunt (CSVd) and chlorotic mottle (CCMVd). Viroids can only be detected using molecular detection methods, as antibodies cannot be made to them, therefore currently separate ELISA tests and DNA hybridisation or PCR have to be carried out to screen chrysanthemum. This strategy would underpin the sustainable supply of healthy propagation material and help to eliminate the primary inoculum for plant virus disease.
1. Develop a TaqMan assay for INSV (CSL, HRI)
2. Assess the varietal susceptibility of AYR, pot and natural season chrysanthemum to WFT transmitted TSWV and INSV (CSL, ADAS, HRI)
3. Examine the existence of mature plant resistance to TSWV and INSV in AYR, pot and natural season chrysanthemum, and investigate the onset of symptom expression (CSL, ADAS, HRI).
4. Determine the effects of thrips biological control agents on pot chrysanthemum infection with TSWV and INSV and on viral loads in both thrips and plants (ADAS, CSL).
5. Develop an ornamentals DNA chip for the generic detection of viruses and viroids infecting propagation material (CSL, HRI).
Project Documents
• Final Report : Epidemiology of viruses of protected crops   (564k)
Time-Scale and Cost
From: 2002

To: 2005

Cost: £391,523
Contractor / Funded Organisations
Warwick - HRI, Horticulture Research International
Allocated - WHRI              
Biological Control              
Disease Control              
Organic Farming              
Pesticide use              
Sustainable Farming and Food              
Sustainable Production              
Fields of Study