Increased content of phenolic compounds in pear leaves after infection by the pear rust pathogen

• Fungus Gymnosporangium sabinae one of the most serious fungal diseases on pear treas.
• Identified and quantified 31 polyphenolic compounds after biochemical change of leaves.
• Infection changes the color and content of the main phenolic compounds.
• Leaves after infection have 1.5 times higher phenolic compounds than not infected.

European pear rust induced by the fungus Gymnosporangium sabinae (Dicks) G. causes yellow to bright orange leaf spots on leaves of pear trees. The aim of this study is to identify and quantify polyphenolic compounds found in pear leaf extracts. Identified were: ten hydroxycinnamates, eight flavonols, nine flavan-3-ols and three arbutin derivatives. Polymeric procyanidins were additionally determined by UPLC-FL. The total content of phenolics in the control healthy green leaf extract was 11,889.98 mg but in the infected leaves it reached 28,573.89 mg in the samples with yellow spots and 11,480.06 mg/100 g dry matter (dm) in the green part of leaves. The yellow spots in pear rust leaves were characterized by increased content of flavanol (catechins and procyanidins) and arbutin compounds compared with the green part of the infected leaves and control healthy leaves.