May 7, 1999 Vineyards in Ontario, Canada are taking a $2-million hit each year from a bacterial disease called crown gall ... and the situation is getting worse. But new biological control techniques may soon put an end to its reign. Crown gall is sweeping across wineries around the world, and is particularly prevalent in Ontario's Niagara region grapes because of the cooler climate. It causes freeze damage, which can provide sites for infection where tumours later develop. It's estimated that 10 per cent of Ontario grape crops are infected with the disease. Problems surrounding grape production in Ontario are being investigated in research centres across the province. For example, at the University of Guelph, Plant Agriculture Prof. Bryan McKersie is using biotechnology to transfer cold resistance to grape vines, which could decrease freeze damage and help protect the plant against crown gall infection.
"We've used a non-pathogenic bacteria to transfer cold resistance to grape vines," says McKersie. "If this reduces freeze damage it could also lower the vine's susceptibility to infection. The plants are in the field now, but it will be a few more years before we have the results."
On the national front, a research team from Agriculture and Agri-Food Canada (AAFC) is giving grape growers a fighting chance against Agrobacterium vitis, the bacteria behind crown gall, by developing a biological control system to prevent the tumours or "galls" that characterize the disease from forming.
The galls surround an infected grape vine's trunk and cut off the plant's nutrient supply, leaving it vulnerable to other diseases and environmental stresses.
Southwestern Ontario vinifera (wine-producing) grape varieties average Agrobacterium infection levels of 40 per cent.
"Right now, there are no effective chemicals available to fight crown gall disease once the vines become infected," says AAFC researcher Dr. Diane Cuppels, one of the team's leading scientists. "We're working on a non-pathogenic strain of the bacterium from South Africa that's shown biocontrol activity against the ‘bad' bacterium."
Field trials indicate the South African strain of the bacterium, called F2/5, is effective in Ontario grapes, although the mechanism by which it protects grape vines is not well understood. But F2/5 is not an ideal biocontrol agent because it's of the same species as the disease-causing pathogen. That means in field conditions, F2/5 could eventually inherit the genes for inducing disease from its pathogenic cousin.
Cuppels and post-doctoral fellow Dr. Steven Walker are using molecular biology to identify and isolate the genes from F2/5 that protect grape vines against tumour formation. Once those genes are found, Dr. Lorne Stobbs at AAFC's Southern Crop Protection and Food Research Centre will use biotechnology to transfer the tumour-suppressing genes into potential bacterial receptors. Finally, field trials will be carried out to evaluate which receptor provides the most effective protection against crown gall infection.
The AAFC research team is supported by the Ontario Research Enhancement Program, a $4-million federally funded research initiative administered by the Research Branch of AAFC with input from the agriculture and agri-food sector, universities and the province. OREP supports 25 research projects in universities and research centres across the province, with the University of Guelph as a major participant. Projects focus on two key areas identified by the agriculture and agri-food community: consumer demand for higher quality safe products and ensuring crop production management systems that are environmentally sustainable.
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