Functional PPO2 mutations: co-occurrence in one plant or the same ppo2 allele of herbicide-resistant Amaranthus palmeri in the US mid-south.

Resistance to PPO inhibitors is widespread across the Mid-southern USA. Highly resistant field populations have plants with multiple mutations. G399A is the most prone to co-occur with other ppo2 mutations in the same allele. Mutation at R128 in the configuration of the PPO2 catalytic domain restrains the co-occurrence of R128G with ΔG210, making ΔG210 + G399A the most plausible, tolerable functional mutation combination to co-occur in the same ppo2 allele.