CELL-DIVISION AS A RESPONSE TO SHOT HOLE INFECTION IN PRUNUS-DOMESTICA - INVOLVEMENT OF FLAVANOLS

Clasterosporium carpophilum the causal organism of shot hole is a seri ous fungal pathogen of stone fruits. Light microscopic studies of prun e leaves indicated that during the early infection process a distinct chlorotic halo is formed showing intense cell division and accumulatio n of flavanols in both spongy parenchyma and palisade cells. This circ ular zone comprised about 1 to 2 mm. In a later stage of infection, th e flavanol-rich cells bordering the necrotic center enlarged strongly up to about 50 pm in diameter and then lost their contact with the dea d cells which finally fell out. Prune leaves contain up to 12 diverse flavanols, the most dominant of which being (+)-catechin. (+)-Catechin as a monomeric flavanol was applied exogenously to in vitro cultivate d tissue of prune. The flavanol stimulated growth preferently by fresh weight increment. It possibly stimulates in concert with auxin the in tense cell division at the early stage of fungal infection and may be involved also in cell enlargement around the necrotic center of shot h ole.