PPO2 Mutations in Amaranthus palmeri: Implications on Cross-Resistance

In Arkansas, resistance to protoporphyrinogen IX oxidase (PPO)-inhibiting herbicides in Amaranthus palmeri S. Wats. is mainly due target site mutations. Although A. PPO-mutations are well investigated, the cross-resistance that each ppo mutant endows weed populations not yet understood. We aimed evaluate response of PPO-resistant accessions, harboring ppo2 mutations ?G210 and G399A, multiple PPO-inhibiting herbicides. Six resistant one susceptible field accessions were subjected a dose–response assay with fomesafen, selected survivors from different fomesafen doses genotyped characterize mutation profile. The level was determined conducted 1 2 times labeled PPO accession higher predicted dose control 50% population (ED50) had frequency ?G210-homozygous survivors. Survivors both mutations, those ?G210-homozygous, incurred less injury at highest rate tested (1120 g ai ha?1). high survivors, individuals + G399A exhibited potential for other new PPO–herbicide chemistries (saflufenacil, trifludimoxazin) generally controlled populations.