Evaluation of biochemical changes and enzymatic activity of sunflower (Helianthus annuus L.) susceptible and resistant lines in response to Sclerotinia disease

Sclerotinia is important fungal disease of sunflower in Iran that affects its yield. In this study, biochemical and enzymatic changes of sunflower lines (C39 and C100) were studied during different times after inoculation of the lines with Sclerotinia fungal isolates (SSU107 and SSKH41) under controlled conditions as a factorial based on completely randomized design (CRD). So, characteristics such as lipids peroxidation and accumulation of malon dialdehyde (MDA), antioxidant enzymes' activity like catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) were studied. The results showed that Sclerotinia disease increased the biochemical and enzymatic changes of the plants infected with fungal isolates. Resistant and susceptible lines also showed a different response to the disease, so that the accumulation of MDA in resistant lines decreased, the least of which was related to resistant line C39 inoculation with the SSU107. In addition ascorbate peroxidase and guaiacol peroxidase enzymes' activities were more in resistant and susceptible lines, respectively. So, the APX enzymatic activity increased in the line C39 and the GPX enzymatic activity increased in the line C100 after inoculation with SSU107 fungal isolate. According to the results of this study, the line C39 showed good partial resistance, because of the lowest level of lipid peroxidation and the highest enzymatic activities that causes resistance mechanism of plant against pathogens.