RESPONSE OF BRASSICA-NAPUS IN TISSUE-CULTURE TO METSULFURON-METHYL AND CHLORSULFURON

A herbicide bioassay based on tissue cultures of Brassica napus L. was evaluated with selected sulfonylurea herbicides. Data were analysed b y fitting the results to a log-logistic dose-response model. Within an experiment, the non-linear regression models were fitted simultaneous ly to the individual dose-response curves. The results obtained showed good response to even low concentrations of herbicide, with detection limits in the range 0.008-0.69 nmol L-1 for chlorsulfuron and 0.02-0. 13 nmol L-1 for metsulfuron. The reproducibility of the assays, on the basis of coefficient of variation of the ED50 values, was found to be 44% for chlorsulfuron and 48% for metsulfuron measurements. Assay of herbicide dissolved in aqueous soil extract showed significant interfe rence from this matrix on the response, requiring a five times dilutio n of the extract to overcome this matrix effect.