Antioxidant response of cucumber leaf tissues treated with prohexadione-Ca to infection with Pseudomonas syringae pv. lachrymans

Abstract

The metabolic response of prohexadione-Ca (Pro-Ca) treated cucumber (Cucumis sativus L.) leaves to Pseudomonas syringae pv. lachrymans (Psl) was analyzed at the local and systemic levels. The activities of antioxidant enzymes such as ascorbate peroxidase (APX), catalase (CAT) and peroxidase (POX) utilizing guaiacol and syringaldazine as well as lipid peroxide level were studied. Observed changes in these parameters were compared to the response induced by benzotiadiazole (BTH) treatment after Psl infection. Cucumber plants pretreatment (priming) with Pro-Ca similarly to BTH priming enhanced the defense response of cucumber leaves to subsequent bacterial infection as shown by the suppression of disease development in comparison to the untreated plants. Pro-Ca priming changed the examined parameters in both pathogen-inoculated leaves and systemic (uninfected) ones depending on Pro-Ca concentration used. However, these changes were pronounced especially in the direct inoculated leaves. In the systemic leaves Pro-Ca pretreatment induced different changes profile in examined parameters than BTH.Obtained results suggested that Pro-Ca as BTH affect the pro-antioxidative metabolism under Psl infection conditions but in a different way. BTH induced mainly APX while Pro-Ca APX and CAT. Strong influence of Pro-Ca on both examined types of POX was also found. The POX utilizing syringaldazine activity indicted that in all examined variants Psl infection affected the lignifications of cell wall. Although the physiological significance of examined pro-antioxidative reactions at the local and systemic levels remains to be elucidated, the presented results support for the first time the protective role of Pro-Ca in defense response of cucumber against P. syringae pv. lachrymans.