传毒昆虫-病毒-寄生性天敌互作中的寄主选择性及机制研究

The sweetpotato whitefly, Bemisia tabaci, is one of the most widely distributed agricultural pests, and B and Q are the two most destructive biotypes (cryptic species) in China. Currently, B. tabaci Q has displaced B in most areas in China and the virus disease from Tomato Yellow Leaf Curl Virus (TYLCV) vectored by B. tabaci occurred simultaneously. Encarsia formosa is an important and widely used parasitoid for whiteflies including B. tabaci worldwide. However, it remains unclear whether TYLCV influences E. formosa parasitizing and selecting B. tabaci B and Q and the related mechanisms has not been reported up to date, which is closely related to the biocontrol efficacy on whiteflies by E. formosa. In this present proposal, the system of B. tabaci-TYLCV-E. formosa is used to study the parasitism on B. tabaci B and Q of E. formosa. The host selection of B and Q coexisted in the healthy and viruliferous tomato plants will be carried out through indoor and outdoor experiments. The differences of plant volatiles from the co-infected of TYLCV and B. tabaci, confirming the components inducing E. formosa. Finally, qPCR technique was used to study the expression levels of related genes in salicylic acid and jasmonic acid pathways, after the tomato plant is infected with TYLCV and/or B. tabaci. The results will be important in the guidance of practical controlling of whiteflies by its parasitoid E. formosa, and also promote the understanding of interactions among virus transmission insect-virus-natural enemy.

烟粉虱Bemisia tabaci是世界性农业害虫，B和Q是为害最严重的两个生物型（隐种）。随着Q烟粉虱在我国多数地区替代B成为优势为害种类，其传播的番茄黄化曲叶病毒（TYLCV）引发的病毒病也随之爆发。丽蚜小蜂Encarsia formosa是烟粉虱的重要寄生性天敌，而TYLCV对丽蚜小蜂寄生和选择烟粉虱B和Q特性的影响及其机制尚不明确。本项目拟以烟粉虱-TYLCV-丽蚜小蜂为研究系统，研究丽蚜小蜂对健康和感染病毒的番茄上饲养的烟粉虱B和Q的寄生特性及二者共存时小蜂的寄生选择性；研究病毒与烟粉虱共同侵染植物时其挥发物的变化及对寄生蜂起引诱作用的重要组分；并通过定量PCR研究其茉莉酸、水杨酸合成途径上相关基因的表达变化，揭示双生病毒对丽蚜小蜂寄生烟粉虱B和Q的影响及其机制。研究结果对于田间释放丽蚜小蜂控制烟粉虱有重要指导意义，也有助于丰富和推动病毒-植物-昆虫-天敌之间复杂互作关系的发展。

烟粉虱Bemisia tabaci是世界性农业害虫，B和Q是为害最严重的两个生物型（隐种）。随着Q烟粉虱在我国多数地区替代B成为优势为害种类，其传播的番茄黄化曲叶病毒（TYLCV）引发的病毒病也随之爆发。丽蚜小蜂Encarsia formosa是烟粉虱的重要寄生性天敌，而TYLCV对丽蚜小蜂寄生和选择烟粉虱B和Q特性的影响及其机制尚不明确。本项目以烟粉虱-TYLCV-丽蚜小蜂为研究系统，研究发现，在健康番茄上，丽蚜小蜂对烟粉虱B的寄生选择性高于Q烟粉虱，然而，番茄植株感染双生病毒TYLCV后影响了该寄主选择性；无论是单独的B/Q烟粉虱或共存于带毒番茄叶片上的B和Q烟粉虱，丽蚜小蜂对Q烟粉虱若虫的选择性高于B烟粉虱，且离体叶片和活体植株上的选择性趋势一致，Y型嗅觉仪也验证了这一结论；进一步研究探索丽蚜小蜂对烟粉虱B和Q、健康和带毒植株的选择性机制，发现植物挥发性物质，特别是萜烯类物质量的变化可能是导致这种选择性差异的内在机制，随后采用化学纯品结合Y型嗅觉仪研究发现，单萜类物质如β-月桂烯、β-罗勒烯和倍半萜类如石竹烯、α-葎草烯等萜烯类物质是导致丽蚜小蜂对带毒番茄上B和Q烟粉虱三龄若虫嗅觉和寄生选择差异显著的关键挥发性物质。最后在植物上喷施外源茉莉酸和水杨酸，发现外源茉莉酸JA能够提升植株防御途径基因的表达量，且诱导增强了丽蚜小蜂的趋性，该种表型的内在机制有待于进一步探索。本项目研究结果对于田间释放丽蚜小蜂控制烟粉虱有重要指导意义，也有助于丰富和推动病毒-植物-昆虫-天敌之间负责互作关系的发展。