マツノザイセンチュウの生活環に関連する糸状菌(II) Fungi associated with Bursaphelenchus lignicolus, the pine wood nematode (II)
マツ健全木の幹からPestalotia, Papularia, Trichodermaが, 枝からPestalotiaとRhizosphaeraが, 健全苗木の茎枝からRhizosphaera, Pestalotia, Cladosporiumが検出され, 材中における糸状菌の潜在が示唆された。線虫の加害によりマツが異常・枯死を起こすと樹体内の糸状菌相は急激に変化し, 枝幹上部にはCeratocystis, Diplodia, Macrophomaが, 幹下部の辺材部にはVerticicladiellaが優占し, 細菌も一時的に異常に増加する。健全木の糸状菌の中ではPestalotiaとRhizosphaeraが線虫増殖に好適でマツ樹体内で線虫の食餌の一つとして役立ちうることが示された。マツが異常を起こしてのちの材中での線虫の増殖にはCeratocystisとDiplodiaが好適である。Ceratosystisは線虫とマツノマダラカミキリ両者の共存関係にもう一つ加わり三者で共存関係を形成することが示唆された。晩秋から早春に異常枯死を起こすマツからはマツノザイセンチュウは検出されず, 材中から糸状菌Amylostereumが優占的に検出され, キパチ類との関連性やマツへの加害性など, 線虫によらない枯損原因の一つとして検討の必要性が示された。
Several fungi, such as Pestalotia, Papularia, Trichoderma, Rhizosphaera and Cladosporium, were constantly isolated from the sound wood of healthy pine trees and seedlings. It seemed certain that the trunks, branches and stems of pine trees were latently infested with these fungi. Microflora changes rapidly within the wood of pine trees killed by the pine wood nematode, Bursaphelenchus lignicolus. Ceratocystis, Diplodia and Macrophoma dominantly occupied the wood of branches and upper part of trunk, instead of the fungi mentioned above. Verticicladiella dominated the sapwood of the lower part of trunk. Some kinds of bacteria also multiplied rapidly within the whole part of dead trees. From the multiplication experiments of the nematode on the agar media and within the sterilized wood, on which the fungi were pre-cultured, four fungi, namely Pestalotia and Rhizosphaera isolated from sound wood of healthy trees and Ceratocystis and Diplodia from dead trees, proved to be favorable to the multiplication of the nematode. It is presumed from the results that Pestalotia and Rhizosphaera are able to serve as a food for the nematode whenever, it multiplies within the wood of healthy pine trees. Within the wood of dead pine trees, Ceratocystis, Diplodia and Macrophoma are utilized by the nematode as its food. Ceratocystis, a kind of blue stain fungi, B.lignicolus, a pine wood nematode, and Monochamus alternatus, a pine wood borer, are closely connected to each other with a correlative relationshiop in their life histories. Ceratocystis is disseminated by M.alternatus to the crown of healthy trees from the dead pine trees together with the nematode. It soon diffuses into the trunk of the trees when they are killed by attack of the nematode, and it serves as a food for the nematode within the wood. A number of perithecia of Ceratocystis are formed on the surface of the pupal chambers of Monochamus. Adults of Monochamus having abundant nematodes and ascospores of Ceratocystis in and/or on their bodies fly out from the dead trees. Amylostereum sp. was detected as a dominant fungal species in wood of the dead pine trees which were killed by an unknown agent other than B. lignicolus during late autumn through early spring.
日本林學會誌 57(6), 184-193, 1975-06-25