The ALS inhibitor herbicides are the main products applied to control Euphorbia heterophylla in the soybean crop; however, resistant biotypes to these herbicides have been identified in Brazil. This research aimed to study the inheritance, number of genes involved in the resistance and the degree of resistance of the homozygous and heterozygous resistant biotypes. Reciprocal crossings (RSs) were carried out between susceptible (S) and resistant (R) parents to obtain F1 seeds. Individuals from F1, F2, RCr and RCs and parents were sprayed with imazethapyr (150 g ha-1). To evaluate the resistance degree, F1 plants and the resistant and susceptible parents were sprayed with imazethapyr (0, 100, 200, 400, 800 and 1,600 g ha-1). F1 plants were totally resistant to the herbicide, demonstrating that resistance is nuclear and dominant. F2 presented high probability for 3:1 segregation, indicating that resistance is coded by a dominant gene. The experiment with F1 plants sprayed with rates of imazethapyr, demonstrated that dominance is complete.
herbicide resistance; hybridization; dominance; inheritance; acetolatate synthase
