植物病原體通過改變宿主植物的氣味來吸引昆蟲媒介,，圖右為被病菌感染的蘋果。
根據(jù)《化學生態(tài)學雜志》上發(fā)表的一項新的研究結(jié)果,，為了吸引昆蟲媒介，植物病原體Candidatus Phytoplasma mali（Candidatus植原體）改變了植物的氣味,，從而確保這一傳染過程能夠得到最大的傳播,。研究人員認為,，這一發(fā)現(xiàn)將有助于研制出新的植物抗蟲方法。
蘋果增生病——能夠?qū)е聡乐氐慕?jīng)濟損失——是由Ca. P. mali引發(fā)的,，它的特點是使植物的枝丫看起來就像女巫的掃帚,，并結(jié)下小而無味的果實，這些果實根本就無法出售,。細胞壁較少的細菌Ca. P. mali在被感染的植物的韌皮部生長,，并且由以韌皮部為食的木虱所傳播。這些木虱在蘋果樹上繁殖,，而新孵化出的成蟲通過食用被感染的植物韌皮而攜帶上Ca. P. mali,。對植物種間外激素——由活的有機體分泌并釋放的化學物質(zhì)，有利于接收者而不利于供體——的嗅覺響應(yīng)之前被認為對于木虱尋找宿主的行為是至關(guān)重要的,。在這項最新的研究中,，被感染以及未被感染的昆蟲的行為與被感染和未被感染的蘋果樹之間的關(guān)系是研究的重點。
德國吉森大學的Mayer CJ與同事針對行為的生物測定使用了一種Y型嗅覺計,，從而記錄昆蟲對未被感染以及被感染的蘋果樹枝丫氣味的響應(yīng),。木虱被放入嗅覺計，用來測定它們是否會選擇放有被感染或未被感染的嫩枝的儀器臂,。研究人員通過PCR證實了昆蟲被感染的狀態(tài),，而學生t檢驗則被用來確定這些結(jié)果在統(tǒng)計學上是否具有意義。
這項研究的主要意義在于發(fā)現(xiàn)被感染的蘋果樹能夠明顯吸引被感染以及未被感染的昆蟲,。病原體的好處在于未被感染的昆蟲將最終被感染,，而已經(jīng)被感染的昆蟲則將吃下更多的病原體，從而增加一棵未被感染的樹最終被感染的可能性,。那些在被感染的蘋果樹上繁殖卻未被Ca. P. mali感染的木虱具有相反的響應(yīng),，并且遭到被感染的植物的抵制，這使作者推測,，被Ca. P. mali感染或許也能夠影響昆蟲的行為,。
利用氣相色譜—質(zhì)譜聯(lián)用分析儀能夠測定蘋果樹釋放的化學物質(zhì),。與未被感染的植物相比,，被感染的蘋果樹能夠產(chǎn)生更多的倍半萜烯β-丁香烯，同時研究人員已經(jīng)證明,，木虱能夠直接被β-丁香烯所吸引,。（生物谷Bioon.com）
生物谷推薦原始出處：
Journal of chemical ecology，34(12):1518-22,，Mayer CJ,，Gross J
Pathogen-induced Release of Plant Allomone Manipulates Vector Insect Behavior.
Mayer CJ, Vilcinskas A, Gross J.
Institute for Phytopathology and Applied Zoology, Justus-Liebig University, Giessen, 35392, Germany.
Infochemicals mediate communication within and between different trophic levels. In this study, we identified a new type of plant allomone induced by a plant pathogen and perceived by its vector insect Cacopsylla picta. This phloem-feeding psyllid is the main vector of Candidatus Phytoplasma mali, a cell wall-lacking bacterium that causes the so-called apple proliferation disease. In a previous study, we showed that newly emerged females of C. picta were attracted by the odor of phytoplasma-infected apple plants (Malus domestica), which release ss-caryophyllene in contrast to uninfected plants. Here, the attractiveness of this sesquiterpene for C. picta was confirmed in both olfactometer bioassays and field studies. Synthetic ss-caryophyllene was highly attractive to newly emerged adults of C. picta both when offered simultaneously with healthy apple odor and without. The psyllid's response was independent of its odor experience and infection status. These results confirm our previously established hypothesis that this phytoplasma manipulates the behavior of its vector insect by changing the odor blend of its host plant. Deployed in apple orchards, sticky traps baited with ss-caryophyllene dispensers caught both males and females of C. picta. Consequently, this new type of infochemical, i.e., a phytopathogen-induced plant allomone, represents a promising compound to develop innovative techniques for monitoring or maybe even mass trapping of C. picta.
