Abstract
The basidiomycete Fomitiporia torreyae (Cha-anatake-modoki) causes a severe trunk rot disease called “Hi-akagare-sei-mizogusare-byo” on the cultivar “Sanbu-sugi” of Cryptomeria japonica in Japan. For a long time, this disease had been reported from limited areas in Chiba Prefecture. In recent years, however, this fungus was also reported to cause disease on another C. japonica cultivar and some other economically important tree species such as Chamaecyparis obtusa and Pyrus pyrifolia var. culta. This fungus is believed to invade trees through dead branches, destroy the cambium layer, and prevent outward growth of the invaded parts. The reason why the Sanbu-sugi cultivar was frequently targeted by the fungus, however, had not been well described. Laboratory studies clarified that this fungus utilizes carbohydrates, which are components of tree tissues, and could grow in a medium with a high glucose/yeast extract ratio and low water potential. Compared to bark in living branches and xylem in dead branches, bark in dead branches and xylem in living branches contain a higher amount of glucose, which might give suitable nutrition for the fungus to grow. The characteristics of this cultivar, in which trunks keep dying branches long-term, might establish adequate conditions for the fungus to invade them. The invaded trunks contained a lower amount of polyphenols, which are supposedly an effective defensive substance.
