A Petri Dish Test For Detection Of Flumetsulam And Mcpa Resistance In Giant Buttercup (Ranunculus Acris Subsp. Acris)

A quick test to enable early detection of flumetsulam and MCPA resistance in Ranunculus acris L. subsp. acris was developed in a series of Petri dish assays and pot trials. Initial experiments used seeds (Experiment 1) or cotyledonary seedlings (Experiment 2) from two R. acris populations of known past herbicide exposure, in Petri dishes containing broad ranges of herbicide concentrations. A further seedling assay (Experiment 3) was carried out using refined ranges of herbicide concentrations and four populations of R. acris of known past herbicide exposure. Percent germination, numbers of new true leaves, root length and green biomass were recorded at intervals after treatment. Results were compared with the LD50 values calculated from dose response pot trials carried out concurrently using the same R. acris populations and herbicides (Experiment 4), in order to validate the results. Percent green biomass 29 DAT at 5 mu M for flumetsulam and 28 DAT at 25-50 mu M for MCPA, gave accurate detection of resistant populations, as shown by high correlations with LD50 values obtained in the pot trials and consistency with results from previous studies.