Multiple-herbicide resistance across four modes of action in wild radish (Raphanus raphanistrum)

Populations of wild radish were collected from two fields in the northern Western Australian wheatbelt, where typical herbicide-use patterns had been practiced for the previous 17 seasons within an intensive crop production program. The herbicide resistance status of these populations clearly established that there was multipleherbicide resistance across many herbicides from at least four modes of action. One population exhibited multiple-herbicide resistance to the phytoene desaturase (PDS)-inhibiting herbicide diflufenican (3.0-fold), the auxin analog herbicide 2,4D (2.2-fold), and the photosystem II-inhibiting herbicides metribuzin and atrazine. Another population was found to be multiply resistant to the acetolactate synthase-inhibiting herbicides, the PDS-inhibiting herbicide diflufenican (2.5-fold), and the auxin analog herbicide 2,4-D amine (2.4-fold). Therefore, each population has developed multiple-herbicide resistance across several modes of action. The multiple resistance status of these wild radish populations developed from conventional herbicide usage in intensive cropping rotations, indicating a dramatic challenge for the future control of wild radish.