Using Indirect Quantitative Seed Bioassay as a Useful Method for Evaluating Herbicide Tolerance in Wheat Cultivars

The purpose of this study was to utilise indirect quantitative seed bioassay and estimation of 50 percent effective concentration (EC50) variable of herbicide active ingeredient (a.i.) as a useful method for evaluating herbicide tolerance of wheat cultivars in breeding programs. Using primary bioassay in petri dish on seedlings of seven wheat cultivars were treated with several concentrations of Metribuzin, Bromoxynil+MCPA, and 2,4-D+MCPA herbicides, maximum tolerable concentration, the tolerantest cultivar and the best trait was selected for bioassay by measuring morphological traits. In second test, the seed bioassay carried out by measuring of different morphological traits upon seedlings of the tolerantest selected cultivar in primary test under eight concentrations of herbicides and control level without herbicide in petri dish. Then EC50 of a.i. calculated based on nonlinear regression. Used herbicides EC50 included Metribuzin, Bromoxynil+MCPA, and 2,4-D+MCPA were estimated at 0.517 and 0.98 litter and 0.285 kg a.i. respectively. According to the results, length of aerial organs was a desirable trait for applying seed bioassay. Quds was the tolerantest cultivar to applied herbicides among the selected cultivar in two step tests and it can be used to estimation of EC50 of a.i..