柑橘黃龍病菌在柑橘木蝨體內的增殖及分布

Abstract

柑橘黃龍病 citrus huanglongbing 為亞洲和非洲地區重要的柑橘病害，引起柑橘黃龍病之病原體 Candidatus Liberibacter asiaticus 為寄生在寄主植物篩管的薄壁細菌，無法以人工方式培養。此病可藉由無性繁殖體的嫁接方式與媒介昆蟲來傳播，在亞洲地區是由亞洲柑橘木蝨 Diaphorina citri Kuwayama 以持續性方式媒介傳播。為瞭解黃龍病菌在柑橘木蝨體內的活動過程及對木蝨之可能影響，應用穿透式電子顯微鏡觀察黃龍病菌在柑橘木蝨體內的循環過程。試驗證實柑橘木蝨從罹病株上獲取黃龍病菌後，需經過約7天的潛伏期才具有傳播能力。黃龍病菌必需先穿過中腸上皮細胞並於中腸細胞內進行增殖，接著進入血腔繼續進行增殖，並逐漸移行至其他組織包括血球、神經、脂肪體、氣管上皮細胞及肌肉等，最後抵達唾腺，屆時柑橘木蝨即具有傳播黃龍病的能力。與健康未受黃龍病菌感染的肌肉細胞相比較，受黃龍病菌感染的肌肉細胞之粒線體數目減少且肌纖維膜受到破壞。證據顯示被黃龍病菌感染的木蝨其壽命和繁殖力會明顯降低。

Citrus huanglongbing (HLB) is a serious citrus disease in Asia and Africa. It is caused by the infection of Candidatus Liberibacter asiaticus (Las), a fastidious bacterium that resides in the sieve tube of host plants. The pathogen is transmitted persistently by the Asian citrus psyllid, Diaphorina citri in Asia. In order to figure out the whole process of Las inside psyllids, and its ill effect on the psyllids. The transmission electron microscopy (TEM) was employes. The psyllids were able to transmit Las to their host plants 7 days after acquisition from the Las-infected plant. Las multiplied first in the midgut epithelial cells of psyllid, and then penetrated through the basal lamina and entered into the hemocoel. Las multiplied again in the hemocoel and then invaded other host tissues, including hemocytes, nervous tissue, fat body, trachea, and muscle. Eventually, Las invaded the salivary gland and the Las-infected psyllids were enabled to transmit Las to other host plants. Symptoms of serious pathogenesis occurred in the muscle tissue. The number of mitochondria in the Las-infected muscle cells was reduced and, the myofilaments and sarcolemma were disrupted. The longevity of Las-infected psyllids was significantly shortened and its fecundity reduced.