(Frontiers Media, 2023) Eceiza, Mikel Vicente; Barco Antoñanzas, María; Gil Monreal, Miriam; Huybrechts, Michiel; Zabalza Aznárez, Ana; Cuypers, Ann; Royuela Hernando, Mercedes; Institute for Multidisciplinary Research in Applied Biology - IMAB; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
The aim of the present study was to elucidate the role of oxidative stress in the
mode of action of acetolactate synthase (ALS) inhibiting herbicides. Two
populations of Amaranthus palmeri S. Watson from Spain (sensitive and
resistant to nicosulfuron, due to mutated ALS) were grown hydroponically
and treated with different rates of the ALS inhibitor nicosulfuron (one time and
three times the field recommended rate). Seven days later, various oxidative
stress markers were measured in the leaves: H2O2, MDA, ascorbate and
glutathione contents, antioxidant enzyme activities and gene expression
levels. Under control conditions, most of the analysed parameters were very
similar between sensitive and resistant plants, meaning that resistance is not
accompanied by a different basal oxidative metabolism. Nicosulfuron-treated
sensitive plants died after a few weeks, while the resistant ones survived,
independently of the rate. Seven days after herbicide application, the
sensitive plants that had received the highest nicosulfuron rate showed an
increase in H2O2 content, lipid peroxidation and antioxidant enzymatic
activities, while resistant plants did not show these responses, meaning that
oxidative stress is linked to ALS inhibition. A supralethal nicosulfuron rate was
needed to induce a significant oxidative stress response in the sensitive
population, providing evidence that the lethality elicited by ALS inhibitors is
not entirely dependent on oxidative stress.
