Raffaelea quercivoraを接種したブナ科樹木4種の菌糸分布と防御反応の比較

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Raffaelea quercivoraに対し感受性の高いミズナラとコナラ, 感受性の低いアラカシとスダジイの防御反応の差異を明らかにするため, 接種後14日目まで組織化学的観察を行なった。その結果, 防御反応として, 材変色域や材変色域と健全域との境界部(反応障壁)にフェノール性物質, 脂質物質, リグニン様物質が集積されることが明らかになった。脂質物質の呈色反応は, アラカシで接種後3日目に観察され10日目に顕著になったが, ミズナラでは接種後7日目に観察され, 14日目でも部分的であった。一方, フェノール性物質とリグニン様物質の呈色反応は感受性の高い樹種のほうが低い樹種よりも早く観察された。さらに, 脂質物質とリグニン様物質が集積した組織より外側の組織では, 菌糸は観察されなかった。これらのことから, 菌糸の伸展は組織内にフェノール性物質や脂質物質, リグニン様物質が集積することによって停止し, 特に脂質物質が組織内に集積する速さがR. quercivoraに対する宿主樹木の感受性に関与していることが推察された。To examine the differences of defense responses to R. quercivora in four Fagaceae species; two susceptible Quercus crispula and Q. serrata and two resistant Q. glauca and Castanopsis cuspidata var. sieboldii, branches inoculated with the fungus were examined histochemically until 14th day after the inoculation. As defense responses, phenolics, lipid compounds and lignin-like compounds were observed either in the discolored sapwood or in the boundary between discolored and sound sapwood. The lipid compounds were observed on the 3rd day and were very noticeable on the 10th day for Q. glauca, while their presence was confirmed on the 7th day but they were still a localized reaction on the 14th day for Q. crispula. On the other hand, both phenolic and lignin-like compound accumulations in the susceptible species were observed earlier than those in the resistant species. Moreover, hyphae were not observed in sound xylem which was outside the xylem where lipid and lignin-like compounds accumulated. These results indicate that hyphae growth of R. quercivora might be prevented by the accumulation of phenolic, lipid and lignin-like compounds in the xylem, and the speed of lipid compound accumulation might be mostly related to the susceptibility of the four Fagaceae species examined to R. quercivora.

Raffaelea quercivoraを接種したブナ科樹木4種の菌糸分布と防御反応の比較

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