ABSTRACT
Quantal response bioassays are useful to identify and monitor shifts in population tolerance. They provide information that can be used for statistical comparisons of entire regression lines and individual dose levels of interest. Although full-scale bioassays are crucial to toxicological research programs concerning resistance, they are impractical for resistance monitoring programs because of the time and resources involved in their completion. Instead, resistance monitoring programs may use only one dose (that is diagnostic or discriminating dose) for screening field populations. Resistance represents one extreme of response, compared with susceptibility, the other extreme. Proper dose placement and adequate sample sizes must always be used in all bioassays done to estimate relative tolerance (or resistance) of populations or strains. Factors that affect the phenotypic expression of genetic resistance might affect not only the results of bioassays done in toxicological experiments but also the results of resistance detection with discriminating doses.
