1 EFFECT OF LIGHT CONDITIONS ON THE RESISTANCE OF CURRENT-YEAR FAGUS CRENATA SEEDLINGS AGAINST FUNGAL PATHOGENS CAUSING DAMPING-OFF IN A NATURAL BEECH FOREST: FUNGUS ISOLATION AND HISTOLOGICAL AND CHEMICAL RESISTANCE

Abstract―Forest gap dynamics affects the light intensity on the forest floor, which in turn may influence defense and survival of tree seedlings. Current-year Fagus crenata seedlings show high mortality under canopy caused by damping-off, on the contrary, they survive pathogen attacks in gaps. However, defense mechanisms against damping-off have not been fully understood in F. crenata. In order to determine the resistance factors that affect mortality in current-year seedlings, we compared seedling survival and chemical and histological characteristics of the hypocotyls of seedlings from closed-stand and forest-edge plots. Damping-off occurred in the current-year seedlings mainly from the end of June to July; the survival rate of the seedlings was higher in the forest-edge plot than in the closed-stand plot. We identified Colletotrichum dematium and Cylindrocarpon sp. as the causative pathogens only under low illumination by performing an inoculation test on the seedling hypocotyls. In the beginning of July, only the seedling hypocotyls from the forest-edge plot exhibited periderm formation. From mid-June to July, seedling hypocotyls from the forest-edge plot accumulated approximately twice the amount of total phenols that was accumulated by the seedling hypocotyls from the closed-stand plot. The ethyl acetate phase of methanol extract