WDC4: Curly Top Virus Biology, Transmission, Ecology, And Management
(Multistate Research Coordinating Committee and Information Exchange Group)
Status: Inactive/Terminating
WDC4: Curly Top Virus Biology, Transmission, Ecology, And Management
Duration: 10/01/2005 to 09/30/2006
Administrative Advisor(s):
NIFA Reps:
Non-Technical Summary
Statement of Issues and Justification
Curly top virus, the most widespread geminivirus in the US, causes significant losses to a range of crops in many states in the western US. The virus disease is vectored by an insect vector (beet leafhopper) and many common weeds are hosts of both virus and vector. Control of the disease has proven difficult. A cooperative effort is essential for coordinating research on this complex disease to have maximum impact. We propose the development of a regional curly top virus working group. This group will meet to assess and prioritize required research on curly top virus genetics, vector biology and genetics, weed ecology, and disease management. The working group will develop an action plan to determine who will accomplish which aspects of the research, including who will work together to seek funding for the highest priority research. The group will also coordinate research to provide preliminary information needed to secure grant funding.
OBJECTIVES:
The objectives of this project are to:
1. Assemble a working group which will include university, government, extension, and commodity-based individuals to assess the current status of curly top and set priorities for research on beet curly top virus.
2. Organize research on beet curly top virus genetics in the western US.
3. Organize research to assess the genetics and biology of populations of the beet leafhopper vector, Circulifer tenellus within the western US.
4. Organize research to study the role of weed hosts in curly top in the western US.
5. Organize research to examine strategies for managing curly top.
PROCEDURES:
1. Over 30 individuals working on different aspects of curly top in the western US have expressed an interest in joining the working group. Several of these have worked (or are working) together on curly top. Those already committed to joining the group include university and government virologists, weed scientists, entomologists, plant breeders, a statistical modeler, and extension scientists, from New Mexico, Arizona, California, Texas, and Washington. Regional stakeholders with a commitment to the working group and its research include the New Mexico Chile Task Force, a group of chile growers and processors, and extension personnel, the California Beet Sugar Association, and the California Curly Top Control Board. We also have enlisted the help of scientific advisors from Nebraska and Oklahoma. The working group will meet yearly to discuss the status of curly top in the western US and present the latest developments in curly top research. In a preliminary meeting funded by the Western Regional IPM Center, the group also discussed where there were gaps in the knowledge of the disease and set priorities for research. The objectives that are presented below were named as prospective research topics by working group members and will likely change somewhat with additional discussions of the working group. The working group will meet during future years to discuss new research findings and present updates on the quest for funding.
2. The ability to manage a virus disease requires an understanding of which virus is causing the disease. Genetic diversity within beet curly top virus (BCTV) has been established in virus isolates infecting sugarbeets throughout the western US. and in chile in New Mexico. Within California, there are efforts underway to study the virus incidence and diversity. These scattered reports suggest that genetic diversity within curly top viruses may be tremendous and will require a concerted effort to identify virus diversity throughout the western US. The working group will attempt to gain funding to study virus genetic diversity throughout the region by sequencing the genome of large numbers of BCTV isolates collected from different crops, weeds, and states.
3. While much research has been done to determine the leafhopper host range, the biology and ecology of the leafhopper in specific locations has changed with alterations in cropping patterns and weed populations. Work is underway to assess how the leafhoppers are overwintering, and whether different populations have different feeding preferences at a statewide level, but this work needs to be expanded to include the entire vector breeding area. Similarly, leafhopper flight patterns have been studied in New Mexico, but need to be expanded to additional areas in the western US.
Preliminary information suggests that beet leafhopper populations from different states vary genetically according to analysis of the mitochondrial DNA. The working group will collect leafhoppers from diverse populations and try to obtain funding to assess the vector leafhopper genetic variability. It is not known whether the leafhopper populations from the different breeding areas are geographically isolated or if they are interbreeding populations. If they are reproductively isolated, then there may be important differences in adaptation to local host plants, host range and preferences, and virus strain-vector specificity. If they are interbreeding populations which exhibit a similar phenotype, then it may be possible to devise broadly based disease control strategies.
4. There are many reports on the weeds hosts of BCTV and its leafhopper vector. However many of these reports are historical, and the weed populations have changed significantly in the last 50 to 80 years since the reports were published. Virus incidence in weeds has been reported for California and New Mexico. The working group has begun studying the weed populations in vector breeding areas, although little is known of the distribution of key weed hosts. The group will try to obtain funding for these types of GIS mapping studies. Already characterized for California, research in New Mexico is studying the ability of certain weeds to serve as overwintering hosts of the leafhopper and virus. The overwintering weed hosts need to be determined for each primary vector breeding area.
5. Curly top has proved very difficult to control. Working group members are studying a variety of methods to manage the disease including biocontrol of the leafhopper vector, impact of insecticide sprays, use of anti-transpirants to deter leafhopper feeding, effectiveness of trap crops, identification of plant resistance to virus and leafhoppers, engineered resistance, and predictive modeling to determine the likelihood of curly top in the next growing season and timing of leafhopper flights. The working group will be able to coordinate management tests in more than one location. In addition, we anticipate that information about the genetics of the virus and vector may lead to novel management strategies.