Detection and quantification of Agrobacterium vitis, causing crown gall in grapevines, from nursery material

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Crown gall of grapevines is caused by the bacterium Agrobacterium vitis (A. vitis) and is an economically important disease in grape-growing regions with a continental climate, such as the Okanagan valley in British Columbia. The disease has been found in many vineyards in the Okanagan valley and seems to be increasing in frequency. The bacteria move inside infected grapevine vessels and cause gall formation in trunks of grapevines. This reduces plant vigour significantly and may cause partial or complete vine death, especially in young vines. Infected plants need to be replaced. However, once infected plants are grown in a vineyard, the bacteria can survive in the vineyard soil for up to 2 years and can subsequently infect newly planted vines. It has been proposed that the bacteria are introduced to the Okanagan valley through the vines the local wine grape industry purchase from plant nurseries. The disease develops after planting of the infected vines into disease-free soil. There is growing concern within the local wine grape industry about introducing the disease into new vineyard locations that are currently disease-free. Many nurseries that supply vines to the Okanagan valley are not required to test if their vines are infected with A. vitis. There is no assay available for the wine grape industry to test the received material for the presence of A. vitis. We are proposing to develop a rapid assay based on identification of a suitable DNA primer set specific to A. vitis for use in a digital droplet polymerase chain reaction (PCR) to detect and quantify A. vitis in new planting material. The method will then be used to index vines from nurseries typically delivering vines to the Okanagan wine grape industry. This will provide the wine grape industry with information on where to obtain disease-free vines and to ensure that only healthy vines producing high yields will be planted in virgin vineyard soil.