Title: Non-target-site based resistance to ALS-inhibiting herbicides in six Bromus rigidus populations from Western Australian cropping fields
Abstract: Bromus rigidus is a common weed species that has increased in cropping fields due to limited control options. During a random field survey in Western Australia, six B. rigidus populations that survived in-crop weed control programs were collected. The study aimed to determine the resistance profile of these six populations.Based on dose-response studies, all six B. rigidus populations had low level resistance to sulfosulfuron and sulfometuron (both sulfonylurea herbicides) while remaining susceptible to other mode of action herbicides. ALS in vitro activity assays revealed no differences in enzyme sensitivity between susceptible and resistant populations, while the use of malathion (a cytochrome P450 inhibitor) in combination with sulfosulfuron caused the resistant populations to behave as the susceptible population did.This study established that these six B. rigidus populations have low level resistance to the ALS-inhibiting sulfonylurea herbicides, but are able to be controlled by other herbicide modes of action. The low level, malathion-reversible resistance, together with a sensitive ALS, strongly suggest that a non-target site, enhanced metabolism is the mechanism of resistance. [Mechelle J. Owen, Danica E. Goggin & Stephen B. Powles (2012). Non-target-site based resistance to ALS-inhibiting herbicides in six Bromus rigidus populations from Western Australian cropping fields. Pest Management Science, online 09 Jan 2012. DOI: 10.1002/ps.3270]
Keywords: Resistance survey; resistance evolution; Bromus spp; ALS resistance