Histochemical visualization of ROS and antioxidant response to viral infections of vegetable crops grown in Azerbaijan

Extremes of environmental conditions, such as biotic stresses, strongly affect plant growth and development and may adversely affect photosynthetic process. Virus infection is especially problematic in crops, because unlike other diseases, its impact cannot be reduced by phytosanitary treatments. The vegetable crops (Solanum lycopеrsicum L, Cucurbita melo L., Cucumis sativus L., Piper longum L., Solánum melongéna L., Vicia faba L.) showing virus-like symptoms were collected from fields located in the main crop production provinces of Azerbaijan. Infection of the plants were confirmed by Enzyme-linked immunosorbent assay using commercial kits for the following viruses: Tomato yellow leaf curl virus, Tomato mosaic virus, Tomato chlorosis virus, Melon necrotic spot virus and Cucumber mosaic virus, Bean common mosaic virus and Bean yellow mosaic virus. Generation sites of superoxide and hydrogen peroxide radicals and activities of enzymes involved in the detoxification of reactive oxygen species (catalase, glutathione reductase, ascorbate peroxidase, guaiacol peroxidase and superoxide dismutase) were examined in uninfected leaves and in leaves infected with viruses. High accumulation of superoxide and hydrogen peroxide radicals was visualized in infected leaves as a purple discoloration of nitro blue tetrazolium and 3,3′-diaminobenzidine tetrahydrochloride. It was found that the activities of APX and CAT significantly increased in all infected samples compared with non-infected ones. Dynamics of GR and Cu/Zn-SOD activities differed from those of CAT and APX, and slightly increased in stressed samples. Electrophoretic mobility profiling of APX, GPX and CAT isoenzymes was also studied.