The European pear psylla, Cacopsylla pyri L. (Hemiptera: Psyllidae), is one of the most serious arthropod pests of pear. Since proper control of this pest is essential, better understanding of the complex plant-pest relationship is mandatory. This research deals with constitutive polyphenolic profiles in leaves of 22 pear cultivars of diverse origin (P. communis, P. pyrifolia, and P. pyrifolia × P. communis) and different resistance to psylla. The study was designed to show which differences in the polyphenolic profile of leaves from resistant and susceptible pear cultivars could be utilized as information in subsequent breeding programs. The results demonstrated that the leaves of Oriental pear cultivars contained much higher amounts of p-hydroxybenzoic acid, ferulic acid, aesculin, and naringin, that, together with detected 3-O-(6″-O-p-coumaroyl)-hexoside, apigenin, apigenin 7-O-rutinoside, and hispidulin, indicated a clear difference between the species and might represent phenolics responsible for psylla resistance.
