AimsStudying biochemical responses and pathogenesis-related gene expression in sunflower-Sclerotinia interaction can shed light on factors participating to disease resistance. Methods and ResultsPartially resistant and susceptible lines were exposed to pathogen culture filtrate. The activity of antioxidant enzymes and proline was much more pronounced in partially resistant line. The more resistant to Sclerotinia sclerotiorum, the less (1,4)--glucanase activity was observed. PDF 1.2 and PR5-1 exhibited higher transcript abundancein the partially resistant line than in the susceptible line. ConclusionsConsidering the dual roles of oxalic acid, activation of the antioxidant system in partially resistant line might lead to suppression of oxidative burst which is beneficial for the growth of fungus at later stages of infection. The ability of the partially resistant line in balancing antioxidant enzymes could reserve H2O2 as a substrate for peroxidase that might lead to lignification. The contribution of (1,4)--glucanase defence responses against Sclerotinia was observed. The roles of SA and JA marker genes were demonstrated in sunflower defence responses. Significance and Impact of the StudyThe time of antioxidant system activation in host is important in order to contribute to defence responses. To date, the changes in the expression of PR1 and PDF 1.2 and contribution of (1,4)--glucanase enzyme in sunflower defence responses were not reported in previous studies.