Abstract
Chlorophyll degradation is a biological process that causes the loss of the typical green color in fruits and leaves of higher plants. This phenomenon may occur in physiological or traumatic conditions, such as abiotic stresses like water shortage or diseases. For instance, after fungal infections, various phytohormones are activated as a response, and they also play a role in chlorophyll breakdown. Diseases cause chlorotic regions where chlorophyll is catabolized into phyllobilins (PBs). Unlike chlorophyll, PBs have a linear tetrapyrrolic structure and can be classified into four groups: non-fluorescent chlorophyll catabolites (NCCs), dioxobilin-type non-fluorescent chlorophyll catabolites (DNCCs), yellow chlorophyll catabolites (YCCs and DYCCs), and pink chlorophyll catabolites (PiCCs and DPiCCs). This thesis investigates the occurrence of chlorophyll degradation in fruit trees such as apples (Malus × domestica Borkh.), either affected by pathogens or during the physiological process of fruit maturation using HPLC-Q-TOF. The identification of PBs in ripening fruits was performed to determine the optimal harvest period for apples. Subsequently, PBs were analysed in the healthy, sick, and senescent leaves of the investigated plants, revealing the metabolic profile of PBs in these fruit trees. The aim was to use these compounds as biomarkers to assess plant health. This research has also contributed to the foundation of a novel branch of metabolomics: "phyllobilomics," a discipline dealing with PBs.