Antioxidant response in Chenopodium album elicited by Ascochyta caulina mycoherbicide phytotoxins

Antioxidant defence responses were evaluated in Chenopodium album plants treated with a mixture of the phytotoxins ascaulitoxin, 2,4,7-triamino-5-hydroxyoctandioic acid (ascaulitoxin aglycone) and trans-4-aminoproline, produced by the pathogenic fungus Ascochyta caulina, previously proposed as mycoherbicide for this noxious weed. The enzymatic and non-enzymatic effects of these phytotoxins on the ascorbate system and on catalase activity were assessed by evaluating their biological and specific activities through spectrophotometric and electrophoretic analyses. In addition, the oxidative status was monitored through evaluating H2O2 content during the time-course. The mixture of toxins induced high levels of H2O2 accumulation resulting in an oxidative burst in the plant cells. Ascorbate peroxidase and catalase had crucial roles in detoxifying H2O2. The persisting metabolic perturbations, however, led to severe necrosis and death of C. album plants. The induced H2O2 production may be generated by the fungus as part of its necrotrophic nature. This study explains the defence responses in C. album to the mycoherbicide, in particular, the ascorbate systems’ components and H2O2 as an index of oxidative stress.