Wherever any herbicide is used it contributes to the development of herbicide resistance. This is true of all herbicides in all crops. Glyphosate is used to control weeds in glyphosate tolerant crops, such as Roundup Ready canola. For this reason, the use of glyphosate tolerant crops will increase selection for glyphosate tolerance in weeds. At the same time selection for resistance to other herbicides that would have been used in alternative crops will be less in glyphosate tolerant crops.
Roundup Ready canola has only been widely grown in Western Australia since 2010, and has generally not replaced all of the non-GM canola grown on individual properties. When herbicide tolerance/resistance develops in plants it can take several generations with selection applied before it is noticed in a population. With other weed management practices being imposed concurrently it could be many years before resistance/tolerance is detected. To the end of 2015 there had not been an increase in detection of glyphosate resistance in weeds that could be attributed to the use of glyphosate tolerant crops.
For further information on the development of herbicide resistance please refer to Herbicide resistance.