Roadside canola in South Australia and Victoria: persistent or transient populations?

Abstract

The commercial release of herbicide resistant cultivars of canola has raised the spectre that canola will become more 'weedy' in the future. One way of addressing this question is through determining if existing volunteer canola populations are the result of repeated spills or from a build up of a seed bank created in situ. The answer could impact on management strategies put in place for controlling roadside canola populations in the southern regions of Australia. Pods and seed were collected from roadside canola populations. DNA was extracted and analysed by PCr using simple sequence repeat primers. The PCR products were separated on a polyacrylamide gel. The results indicated that larger populations were more likely to have several DNA profiles present, whereas smaller populations were more likely to contain a single genotype. When we compared maternal (pod) DNA with the offspring (seed) the fingerprints were always identical. This suggests that outcrossing is rare in roadside canola populations, even when more than one cultivar is present in the population. This finding is consistent with published research showing that canola plants have a high level of selfing and restricted paternity shadows. Therefore, the spread of herbicide tolerance genes between canola plants along roadsides would be slow and provide plenty of opportunities for control to be undertaken.