A novel mutation in SoIAA20 confers cross-resistance to 2,4-Dichlorophenoxyacetic acid and other auxinic herbicides in Sonchus oleraceus.

Background: 2,4-Dichlorophenoxyacetic acid (2,4-D) and other auxinic herbicides are important for weed control in cropping systems globally. Weeds with resistance to 2,4-D and other auxinic herbicides have evolved, including several populations of Sonchus oleraceus from multiple sites in Australia. We report the underlying mechanism in these populations that gives rise to auxinic herbicide resistance.

Point mutations including a novel Pro-197-Phe mutation confer cross-resistance to acetolactate synthase (ALS) inhibiting herbicides in Lactuca serriola in Australia.

Background: Control of prickly lettuce has become increasingly difficult for lentil growers in southern Australia because of widespread resistance to common herbicides, a lack of alternative herbicide options and the prolific production of highly mobile seed. This study aimed to quantify acetolactate synthase (ALS)-inhibiting herbicide resistance in the Mid North (MN) and Yorke Peninsula (YP) of South Australia, characterize the resistance mutations present and investigate population structure and gene flow in this species.

Results: Resistance was identified in all populations tested, with average survival of 92% to chlorsulfuron and 95% to imazamox + imazapyr.