Apera spica‐venti in the Czech Republic develops resistance to three herbicide modes of action

Abstract

AbstractInvestigation of molecular mechanisms of herbicide resistance to three modes of action was carried out in a population of Apera spica‐venti with resistance to herbicides inhibiting acetolactate synthase (ALS), acetyl‐CoA‐carboxylase (ACCase) and inhibitors of photosystem‐II (PSII). Greenhouse experiments were conducted to detect and characterize resistance pattern to pyroxsulam (ALS inhibitor), pinoxaden (ACCase) and chlorotoluron (PSII) using the recommended rate of each herbicide alone and in tank‐mix, sequential application and dose–response tests. Metabolic detoxification and/or reduced herbicide uptake and translocation studies were conducted using dose–response tests with the herbicides in combination with malathion. After treatment, leaves from surviving plants were collected for pyrosequencing to identify target‐site mutations in specific regions of ALS, ACCase and psbA genes. Among 32 analysed plants, target‐site mutations in specific regions were detected for ALS and ACCase gene, but no psbA mutations were found. Dose–response assay showed high resistance factors for pyroxsulam (RF = 269.4), pinoxaden (RF = 66.3), but lower for chlorotoluron (RF = 14.3). Testing for metabolic detoxification by pre‐treatment with malathion resulted in an increased susceptibility to pinoxaden in all doses, some increased susceptibility to chlorotoluron at the highest doses and no difference for pyroxsulam. Our results indicate that while target‐site mutations were present for ALS and ACCase sites of action, metabolic detoxification does play a role for pinoxaden resistance. This research provided key insights into the resistance mechanisms in Apera spica‐venti and will be important for developing control strategies for this weed in the Czech Republic.