Schrotschuss-infektion bei der Sauerkirsche: Flavanole als Schutzbarriere

The cultivar 'Schattenmorelle' (Prunus cerasus L.) is severely affected by shot hole (Clasterosporium carpophilum) when grafted on Prunus avium (clone Limburger), however, it is highly resistent when grown on own roots. Total flavanoids were highest in infected leaves of the grafted tree. As shown by light microscopy, the increase was mainly due to a denser flavanol staining just around the necrotic infection center. Staining was performed with the highly selective flavanol reagent p- dimethylaminocinnamaldehyde (DMACA). The flavanol pattern as determined by HPLC-CRD technique consisted of the monomers epicatechin (+)-catechin, and the oligomers B2, C1 including a tetrameric epicatechin. These catechol-type flavanols were mainly responsible for the increased antioxidative properties of extracts from infected leaves as compared with healthy ones. Leaching of these flavanols in the cells around the shot hole center is supposed to be stimulated by abscisic acid (ABA). As evidenced by callus cultures, (+)-catechin as a growth promoter would be useful in counteracting ABA effects.