The effect of silicon on antioxidant metabolism of wheat leaves infected by P yricularia oryzae

This study investigated whether the increase in wheat resistance to blast, caused by P yricularia oryzae , potentiated by silicon ( S i) is linked to changes in the activity of antioxidative enzymes. Wheat plants (cv. BR 18) were grown in hydroponic culture with either 0 (– S i) or 2 m m (+ S i) S i and half of the plants in each group were inoculated with P . oryzae . Blast severity in the + S i plants was 70% lower compared to the − S i plants at 96 h after inoculation (hai). Superoxide dismutase ( SOD ), catalase ( CAT ), peroxidase ( POX ), ascorbate peroxidase ( APX ) and glutathione‐S‐transferase ( GST ) activities were higher in the leaves of the − S i plants compared with the + S i plants at 96 hai. This indicates that other mechanisms may have limited P . oryzae infection in the + S i plants restricting the generation of reactive oxygen species, obviating the need for increased antioxidative enzyme activity. In contrast, glutathione reductase ( GR ) activity at 96 hai was higher in the + S i plants than in the − S i plants. Although the inoculated plants showed significantly higher concentration of malondialdehyde ( MDA ) than the non‐inoculated plants, lower MDA concentrations were observed in the + S i plants compared with the − S i plants. The lower MDA concentration associated with decreased activities of SOD , CAT , POX , APX and GST , suggest that the amount of reactive oxygen species was lower in the + S i plants. However, GR appears to play a pivotal role in limiting oxidative stress caused by P . oryzae infection in + S i plants.