ベッコウタケ接種に対する生立木樹幹二次木部の反応

susceptibility to infection

This study aimed to clarify the factors that influence tree susceptibility to infection by the white-rot fungus Perenniporia fraxinea, by inoculating it into stems of four tree species at butt and breast height, and comparing the alterations in the xylem three to five months after inoculation. The four tree species include Robinia pseudoacacia, Cerasus sargentii, Ulmus davidiana var. japonica and Picea glehnii; the former two species are easily infected by this fungus, whereas the latter two species are not. Polymerase chain reaction (PCR) analysis detected the inoculated fungus only in the butt xylem of R. pseudoacacia and C. sargentii and the cell walls in the butt xylem tissues of these species were eroded by hyphae. Other xylem alterations (e.g., water accumulation and cell occlusion) differed among tree species, whereas no apparent difference was observed between butt and breast height. For example, water accumulation occurred in the discolored wood tissues around the inoculated holes in both R. pseudoacacia and U davidiana var. japonica, while dehydration occurred in the light-colored wood tissues around the inoculated hole in P. glehnii. In the vicinity of the inoculation holes, resin deposits formed in P. glehnii, whereas cell occlusions by tyloses/gums occurred in the other three species. These results suggest that susceptibility to P. fraxinea infection differs not only among tree species but also between heights above ground. It is likely that no particular response to fungal inoculation in the xylem tissues of these four tree species is closely associated with their susceptibility to the infection by P. fraxinea.

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