"The oilseed mustards known as canola or rapeseed (Brassica napus and B. rapa) are the same species as some vegetable crucifers and are so closely related to others that interspecific and intergeneric crossing can occur. Intraspecific crosses (within the same species) readily occur among the following: [1] B. napus canola with rutabaga and Siberian kale, [2] B. rapa canola with Chinese cabbage, Chinese mustard, pai-tsai, broccoli raab, and turnip. Interspecific crosses (between different species) can occur among the following: [1] Occur readily: B. napus canola with Chinese cabbage, Chinese mustard, pai-tsai, broccoli raab, and turnip, [2] Occur more rarely: B. napus or B. rapa canola with the B. oleracea cole crops (cabbage, kohlrabi, Brussels sprouts, broccoli, cauliflower, collards, and kale). Intergeneric crosses (between species of different genera) are possible with varying degrees of probability: B. napus or B. rapa canola with wild and cultivated radish (Raphanus raphanistrum and R. sativus). Many factors affect the probability of an interspecific cross, but the most important is proximity of the two species. Many interspecific crosses need to occur for a few to succeed. Thus, hybrid seeds rarely are detected more than 50 meters (165 feet) from the pollen-supplying parent. Because both wind and insects transfer pollen, very rare outcrosses can be detected up to 4 kilometers (2.4 miles) away under special circumstances. However, a distance of 2 kilometers (1.2 miles) should be sufficient for stock seed production. Although it is relatively easy to maintain adequate distance between fields with pinning maps, other sources of canola seed present a greater threat to vegetable seed growers. The two greatest threats are canola seed blown from vehicles onto road shoulders and volunteers in fields previously planted to canola. Detecting and eliminating volunteers from a 2-kilometer radius around a seed field would be onerous and perhaps impossible. The introduction of genetically modified, herbicide-tolerant canola also constitutes a threat to vegetable seed production. Herbicide resistance is unlikely to become established in weedy species or seed crops. However, transgenes can be detected at very low frequency and would make a seed crop unsuitable for some markets. The best solution for introduction of canola into the Willamette Valley would be to maintain zones free of canola plantings and from traffic carrying canola seeds to crushing plants. "--P. [1].