Mwando Nelson L, Tamiru Amanuel, Nyasani Johnson O, Obonyo Meshack A O, Caulfield John C, Bruce Toby J A, Subramanian Sevgan
International Centre of Insect Physiology and Ecology, P. O. Box 30772-00100, Nairobi, Kenya.
Department of Biochemistry and Molecular Biology, Egerton University, P. O. Box 536-20115, Egerton, Kenya.
J Chem Ecol. 2018 Aug;44(7-8):681-689. doi: 10.1007/s10886-018-0973-x. Epub 2018 Jun 2.
Maize lethal necrosis is one of the most devastating diseases of maize causing yield losses reaching up to 90% in sub-Saharan Africa. The disease is caused by a combination of maize chlorotic mottle virus (MCMV) and any one of cereal viruses in the Potyviridae group such as sugarcane mosaic virus. MCMV has been reported to be transmitted mainly by maize thrips (Frankliniella williamsi) and onion thrips (Thrips tabaci). To better understand the role of thrips vectors in the epidemiology of the disease, we investigated behavioral responses of F. williamsi and T. tabaci, to volatiles collected from maize seedlings infected with MCMV in a four-arm olfactometer bioassay. Volatile profiles from MCMV-infected and healthy maize plants were compared by gas chromatography (GC) and GC coupled mass spectrometry analyses. In the bioassays, both sexes of F. williamsi and male T. tabaci were significantly attracted to volatiles from maize plants infected with MCMV compared to healthy plants and solvent controls. Moreover, volatile analysis revealed strong induction of (E)-4,8-dimethyl-1,3,7-nonatriene, methyl salicylate and (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene in MCMV-infected maize seedlings. Our findings demonstrate MCMV induces changes in volatile profiles of host plants to elicit attraction of thrips vectors. The increased vector contact rates with MCMV-infected host plants could enhance virus transmission if thrips feed on the infected plants and acquire the pathogen prior to dispersal. Uncovering the mechanisms mediating interactions between vectors, host plants and pathogens provides useful insights for understanding the vector ecology and disease epidemiology, which in turn may contribute in designing integrated vector management strategies.
玉米致死坏死病是玉米最具毁灭性的病害之一，在撒哈拉以南非洲地区可导致高达90%的产量损失。该病害由玉米褪绿斑驳病毒（MCMV）与马铃薯Y病毒科的任何一种谷类病毒（如甘蔗花叶病毒）共同引发。据报道，MCMV主要通过玉米蓟马（西花蓟马）和葱蓟马传播。为了更好地了解蓟马传播媒介在该病流行病学中的作用，我们在四臂嗅觉仪生物测定中研究了西花蓟马和葱蓟马对从感染MCMV的玉米幼苗中收集的挥发物的行为反应。通过气相色谱（GC）和GC联用质谱分析比较了感染MCMV的玉米植株和健康玉米植株的挥发物谱。在生物测定中，与健康植株和溶剂对照相比，西花蓟马的雌雄两性以及雄性葱蓟马对感染MCMV的玉米植株挥发物均表现出显著的趋性。此外，挥发物分析显示，感染MCMV的玉米幼苗中（E）-4,8-二甲基-1,3,7-壬三烯、水杨酸甲酯和（E,E）-4,8,12-三甲基十三碳-1,3,7,11-四烯有强烈诱导。我们的研究结果表明，MCMV会诱导寄主植物挥发物谱的变化，以吸引蓟马传播媒介。如果蓟马取食感染植株并在扩散前获取病原体，那么其与感染MCMV的寄主植物接触率的增加可能会增强病毒传播。揭示介导传播媒介、寄主植物和病原体之间相互作用的机制，为理解传播媒介生态学和病害流行病学提供了有用的见解，进而可能有助于设计综合传播媒介管理策略。
