馬拉巴栗作為樹木褐根病菌接種模式及檢定植物之研究

Malabar chestnut as a model and bioassay plant for Phellinus noxius brown root rot disease

過往有關樹木褐根病菌（Phellinus noxius）的病原性檢定常常不容易進行或需花費很長的時間，因此本研究旨在篩選及測試，以求找到高敏感且發病反應快速之模式植物。結果從43種候選樹木中，發現馬拉巴栗幼苗可供作為樹木褐根病菌快速接種及病原性檢定之應用。其接種樹木褐根病菌的方法係使用麥粒培養基菌種並利用消毒過之電鑽對馬拉巴栗幼苗莖部鑽孔，再填充入該菌種後以石蠟膜或水性矽膠包覆即告完成。利用此一馬拉巴栗模式植物接種多株之樹木褐根病菌都可在1至2週之內觀察到病菌感染發病之病徵，包括莖部之莖腐、樹皮凹陷、褐化，以及枝葉之黃化及最終之萎凋。在接種原培養基之比較上，發現麥粒培養基養出之菌種比添加養分鋸木屑培養基養出者，表現較優。經切半解剖接種點之莖部，則可見內部組織呈淡褐色水浸狀，並可在顯微鏡下觀察到大量褐根病菌菌絲。此一利用馬拉巴栗作為接種模式植物之方法具有：（1）高敏感度、（2）高材料充足性、（3）接種操作容易、（4）病徵快速呈現、（5）具特有病徵等優點，故可供未來進行病原性快速檢定及防治藥劑初步篩選測試之應用。作者即以殺菌劑注射入馬拉巴栗莖部，同時接種褐根病菌，觀察藥劑之防治成效。因其反應快速，故可供多數藥劑或多種藥劑組合之快篩測試。

"Previously the pathogenicity tests for suspected brown root rot pathogen (Phellinus noxius) were not easy to conduct and took a very long time. For these reasons, we tried to screen from 43 candidate trees and found a very sensitive plant, the Malabar chestnut (Pachira macrocarpa (Cham. & Schlecht.) Walp.), to use as a bioassay or model plant for this pathogen. The inoculation method with an electric drill followed by insertion of wheatoat culture inoculum and sealed with parafilm or wettable sealer makes this bioassay with Malabar chestnut very easy to conduct. With this simple, rapid method, model plants expressed infection symptoms within 1~2 weeks. External symptoms consist of stem rot, sunken bark, browning, and leaf chlorosis and wilting, while internal symptoms included water-soaking and browning of stem tissues. Inoculation from wheat-oat medium performed the best, much better than the enriched sawdust medium. In conclusion, the Malabar chestnut model as a disease bioassay plant fulfilled the following criteria: (a) high sensitivity; (b) high availability of plant materials; (c) ease of operation; (d) rapid expression of symptoms; and (e) exhibition of specific symptoms. On the basis of this model plant, new fungicides for controlling brown root rot disease were injected into the stem of Malabar chestnut, and the inoculum was simultaneously inoculated to study their control efficacy and fungicidal dynamics in the plant. This plant model can be utilized for the rapid screening of fungicides or their combinations for their effectiveness against brown root rot disease."