Oxidative stress in interactions between Avena sativa L. and Drechslera spp.

Abstract

Lipid peroxidation occurs in the early stages of oat leaf blotch development after inoculation with Drechslera avenae and Drechslera siccans. Unsaturated fatty acids decreased in leaves of Avena sativa cv. Erbgraf, while saturated fatty acids remained unchanged. This is in agreement with the malondialdehyde production. Lipid peroxidation was accompanied by a marked increase of lipoxygenase activity. Peroxidase and superoxide dismutase activities increased concomitantly 14 h post inoculation. An increase of ascorbic acid and tocopherol in inoculated leaves and a decline in the amount of glutathione are indicators of an increased demand for detoxification of reactive oxygen species in the early stages of pathogenesis. In contrast to all these changes, observed after inoculation with the highly virulent D. avenae and D. siccans, there were no such changes after inoculation with the weakly virulent D. nobleae and D. graminea where enzyme activities and antioxidant titres remained at the level of the non-inoculated check. It appears that free oxygen radicals are not part of a defence against the pathogens but are associated with pathogenesis.