黄龙病侵染增强沙糖橘对柑橘木虱吸引作用机制的初步研究

Preliminary research on the mechanism underlying the increased attraction of Diaphorina citri for Citrus reticulate Blanco.cv.Shatangju infected with huanglongbing

【目的】黄龙病是柑橘最严重的传染性病害,柑橘木虱Diaphorina citri Kuwayama是黄龙病的媒介昆虫。与健康橘树相比,感染黄龙病的橘树对木虱的吸引作用显著增强,本研究目的是探明病树挥发物的改变是否与此现象有关。【方法】在前期分析健康和染病沙糖橘Citrus reticulate Blanco.cv.Shatangju嫩梢挥发物成分变化的基础上,分别在室内外测定部分差异较大的化合物单体标样及其混合物对柑橘木虱的吸引效果。【结果】雌虫对α-蒎烯(1μL/mL)、γ-萜品烯(0.01μL/mL)和芳樟醇(0.1μL/mL)具有显著的正趋性,但对柠檬烯各浓度均未表现出明显的趋性;雄虫对4种单体标样所有浓度均未表现出显著的趋性。将各种化合物按其有效浓度混合后,雌虫对6种混合物均有显著的正趋性,其中,对γ-萜品烯(0.2μL/mL)+α-蒎烯(0.8μL/mL)+芳樟醇(0.3μL/mL)具有极显著正趋向选择;雄虫对4种混合物有显著的正趋性。将化合物单体及其混合物作为诱剂,在九里香Murraya paniculata L.上测定其诱集效果。结果表明,单一物质均无显著效果,但15种混合物中有5种诱到的木虱数量显著多于对照。将其中3种混合物γ-萜品烯(20μL/mL)+α-蒎烯(80μL/mL)+芳樟醇(30μL/mL)、γ-萜品烯(2μL/mL)+α-蒎烯(8μL/mL)+芳樟醇(3μL/mL)和γ-萜品烯(20μL/mL)+芳樟醇(30μL/mL)在橘园进行测试,结果表明,3种诱剂诱到的木虱数量均显著增加。【结论】α-蒎烯、γ-萜品烯含量增加可能是沙糖橘病树对木虱吸引作用增强的部分原因,这些物质有望用于制备柑橘木虱的引诱剂,但其最佳配比还有待进一步研究。

[Aim]To determine whether infection of the‘Shatangju’variety of Citrus reticulate(Citrus×aurantium L.)with the Asian form of huanglongbing(HLB),a serious disease of citrus associated with the phloem-limited bacterium‘Candidatus Liberibacter asiaticus’(CLas),increases the attractiveness of infected plants to the Asian citrus psyllid(ACP),Diaphorina citri Kuwayama.[Methods]Responses of male and female ACP to volatiles(linalool,limonene,α-pinene,andγ-terpinene)emitted by infected,and pathogen-free,seedlings,indicate that those from infected seedlings were not significantly more attractive to females.In a previous study,volatile compounds from young shoots of pathogen-free and‘CLas’-infected‘Shatangju’mandarins were analyzed.In this study,the attractiveness of several chemical components that were elevated in infected plants,and their mixtures,were tested in both the laboratory and the field.[Results]Males were not attracted to any of the chemicals tested but females were significantly attracted toα-pinene(1μL/mL),γ-terpinene(0.01μL/mL)and linalool(0.1μL/mL),but not to limonene at the concentrations tested.Females were also significantly attracted by 6 mixtures of the above chemicals.Of these mixtures,γ-terpinene(0.2μL/mL)+α-pinene(0.8μL/mL)+linalool(0.3μL/mL)was the most attractive.Males were not attracted to any of the individual chemicals tested,but were significantly attracted by 4 mixtures.Compound monomers and their mixtures were placed in bottle traps in Murraya paniculata(L)Jack trees and the number of insects caught by each lure was compared.The results indicate that 5 of the 15 mixtures were significantly more attractive to D.citri adults than the others,whereas none of the single compounds was significantly more attractive.Three mixtures;γ-Terpinene(20μL/mL)+α-Pinene(80μL/mL)+Linalool(30μL/mL),γ-Terpinene(2μL/mL)+α-Pinene(8μL/mL)+Linalool(3μL/mL),andγ-Terpinene(20μL/mL)+Linalool(30μL/mL),were then tested in a citrus orchard.After 10 days,the average numbers of adults captured in traps using these mixtures was significantly higher than the number captured in control traps.[Conclusion]These findings suggest that the attractiveness of CLas-infected mandarin trees to D.citri is,in part,enhanced by the higher than normal levels ofα-pinene andγ-terpinene emitted by infected plants.It may,therefore,be feasible to use these chemicals to trap the D.citri in orchards.