Comparison of methods to determine the tolerance of maize cultivars and inbred lines to sulfonylurea herbicides

Over several years field trials have been compared with two different bioas says in order to determine the sensitivity or tolerance of maize hybrids an d inbred lines against rimsulfuron and nicosulfuron. Bioassays proved to be suitable methods to determine the tolerance of maize hybrids and inbred lines against the sulfonylurea herbicides tested. In tw o different methods either leaf fresh mass (greenhouse) or the sum of shoot and root dry mass (growth chamber) have been assessed. Both bioassays clea rly demonstrated differences in tolerance of the hybrids and inbred lines t ested. The method in the greenhouse proved to be easy and timesaving. The b ioassay conducted in the growth chamber gave consistent results because of the standardised trial design. Crop tolerance trials in the field gave varying results. Factors with negat ive influence on the crop tolerance like low temperature after treatment or treatment of already damaged plants gave similar results like in the bioas says. However in field trials with favourable growing conditions sensitive cultivars and inbred lines were not affected by the herbicides tested.