Assessing the Susceptibility of Asian Species of Lauraceae to the Laurel Wilt Pathogen Raffaelea lauricola

亞洲樟科植物對樟科萎凋病菌Raffaelea lauricola之感病性評估

施欣慧(Hsin-Hui Shih) ； Caroline E. Wuest ； Stephen W. Fraedrich ； Thomas C. Harrington ； 陳啟予(Chi-Yu Chen)

《台灣林業科學》 33卷3期 (2018/09) Pp. 173-184

https://doi.org/10.7075/TJFS.201809_33(3).0001

摘要

Laurel wilt, caused by Raffaelea lauricola, was discovered in the southeastern USA in 2004, and has been responsible for the death of many indigenous North American tree and shrub species in the family Lauraceae. Symptoms of the disease are typical of vascular wilts, in which woody xylem becomes discolored and nonfunctional due to infection by the fungus, and foliage subsequently dies due to a lack of water. The vector of R. lauricola is an ambrosia beetle, Xyleborus glabratus, and trees become infected when beetles bore into tree stems and branches and release fungal spores from their oral mycangia. The ambrosia beetles produce brood in the trees after wilting. Although the fungus and beetle are native to Asia, laurel wilt has not been reported on plant species native to Asia. The purpose of this study was to assess the susceptibility of Asian species in the Lauraceae to laurel wilt. Most Asian species (Cinnamomum camphora, C. osmophloeum, Machilus zuihoensis, M. thunbergii, C. jensenianum) developed only a light pale-gray discoloration in the sapwood following inoculation, but no other symptoms were observed. However, partial wilt of branches was observed in some inoculated plants of 2 Asian shrub species (Lindera strychnifolia and a Phoebe sp.). Raffaelea lauricola was isolated from discolored xylem of many of the inoculated species. Compared to North American lauraceous species such as redbay (Persea borbonia), the Asian species are more resistant to laurel wilt, but all inoculated host plants showed some level of susceptibility.

關鍵字

laurel wilt ； Raffaelea lauricola ； Asian Lauraceae ； inoculation

並列摘要

樟科萎凋病（病原菌：Raffaelea lauricola）在2004年於美國東南部發現，會造成數種原生於北美地區許多種樟科喬木與灌木的嚴重危害。此病害為典型的維管束萎凋病，病原菌會使木質部變色、喪失輸送水分的功能，最後引起樹木落葉、萎凋死亡。病原菌R. lauricola的傳播媒介為一種菌蠹蟲—Xyleborus glabratus，其會鑽入樹木的枝幹中蛀蝕，並由口部的儲菌器釋放出真菌孢子。雖然前人研究顯示此病害的病原菌和媒介昆蟲皆源自於亞洲地區，但卻不曾在亞洲有嚴重危害樟科植物之報導。因此，本研究目的主要針對數種亞洲樟科植物對樟科萎凋病菌的感病性測試。接種試驗結果顯示，選定的亞洲樟科植物：樟樹（Cinnamomum camphora）、土肉桂（C. osmophloeum）、香楠（Machiluszuihoensis）、紅楠（M. thunbergii）和野黃桂（C. jensenianum），接種病原菌R. lauricola後，於邊材組織會出現輕微淡灰色的變色，但未出現其他病徵。相反的，另兩種亞洲樟科植物，烏藥（Linderastrychnifolia）和一種楠屬植物（Phoebe sp.），則於枝條上分別出現40%和30%的部分萎凋。多數接種植物的變色邊材組織皆可分離到病原菌。此試驗結果和北美樟科植物如：Persea borbonia相比，亞洲樟科植物對樟科萎凋病菌具有較高的抗病性，但不同的樹種仍有不同程度的感病性。

並列關鍵字

樟科萎凋病 ； Raffaelea lauricola ； 亞洲樟科植物 ； 接種