Mar. 15, 1999 Current methods to detect viruses in grapes and other fruit crops may soon be replaced with a faster, cheaper and easy-to-use technique. Known as reverse transcriptase polymerase chain reaction (RT-PCR), the technique has identified grapevines infected with six of the most common viral diseases that hamper world trade. Based on the success of the new test to date, it may someday become the international standard for plant virus detection.
The research team looking at the technology includes University of Guelph Botany Prof. Annette Nassuth, and Château des Charmes Wines research scientist Dr. John Paroschy, in collaboration with Centre for Plant Health (CPH) researchers in British Columbia.
"The grape virus detection system is a model system which can be applied to other fruit crops," says Paroschy.
For example, conventional tests for the "corky bark" grape virus, which causes the bark to bloat, and stem-pitting, take three years before growers can get results. And at $1,500 per plant, the current test is a strain on growers' and nurseries' pocketbooks. But the new method takes less than a week and should cost under $25 per plant.
Faster diagnosis also opens up opportunities to import and export new varieties in winter and test them before spring, when they can be propagated.
PCR can make millions of copies of viral genetic material so it can be easily detected. PCR is common in human medical applications, but only recently have lower prices and advances in technical knowledge warranted its use for plant viruses.
Under the current system, samples of plants suspected of disease are sent to the CPH, where the samples are grafted onto large acreages of indicator plants. They must be grown for three years, and only then will symptoms appear. However, the new test only requires freezer storage space, saving acres of valuable crop land.
For plants, PCR may prove to be a more reliable diagnostic test than the conventional grafting techniques. If all six viruses could be detected from one sample test tube, the "multiplex"PCR technique will minimize handling, labour and potential for contamination.
"The new system replaces long-term diagnostic tests with a simple yes or no," says Nassuth. "We want a practical, useable test that's acceptable to regulatory agencies."
CPH is comparing the PCR technique to the current system and verifying its validity. So far, the new test has yielded promising results.
This research is sponsored by Château des Charmes Wines Limited, with financial and technical support from the National Research Council's Industrial Research Assistance Program.
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