A DNA-based forensic type test developed in Australia will provide vegetable growers with a valuable tool to help manage clubroot, one of the most costly diseases of brassica vegetables. Clubroot is estimated to wipe out about 10% of brassica vegetable production worldwide. Designed for soil, water, and plant material, this technology can be used to test fields to get a measure of potential yield loss due to clubroot, and to test water sources and nursery stock for possible contamination with the clubroot organism. The Victorian Department of Natural Resources and Environment is already providing growers with a commercial service based on the diagnostic tests developed in this research project.

The organism that causes clubroot is a soil-borne protozoan which can persist for twenty years and can be inadvertently transported in contaminated irrigation water and soil. The difficulties of controlling clubroot, together with the lack of hygiene practices to avoid its spread, make this disease one of the most significant impediments to efficient production of brassica crops. There are several control measures growers can use to manage clubroot but they are costly and dependent on the soil concentration of the clubroot. Spores. However, growers can use the DNA test to quickly determine the quantity of clubroot spores in their fields which gives a measure of potential disease and yield loss. This then enables them to make informed decisions about which control measures are the most cost-effective, depending on the disease risk, potentially saving time and money where control was unnecessary or saving the crop from serious damage by clubroot. Water and nursery stocks can also be tested to prevent contamination of uninfected areas.

The diagnostic test, which has proved to be quick, reliable, accurate, and able to detect minute quantities of the Plasmodiophora in soil, water, and plant samples, has attracted worldwide attention. Negotiations are currently under way with Horticulture Research International (Wellesbourne, England) and the UK Department of Environment, Food, and Rural Affairs to develop an on-farm test kit for clubroot. This kit will enable growers to do preliminary on-farm tests which will indicate whether they need more accurate laboratory tests to determine the clubroot status of their farms. The clubroot diagnostic assay developed in Australia is seen as the ‘gold standard’ for clubroot detection worldwide and Australian expertise is considered vital to the successful development of an on-farm kit.

This project has been funded by Hort Innovation, using the research and development levies listed below and contributions from the Australian Government. Hort Innovation is the grower-owned, not-for-profit research and development corporation for Australian horticulture.

• Vegetable Fund