Effects Of PVY-infected Tobacco On The Behavior And Development Of Myzus Persicae

Potato virus Y(PVY)is widespread all over the world.The occurrence and prevalence of PVY severely restricts and threatens the safe production of commercial crops such as tobacco.In the long-term co-evolution process of virus-insect-host plant,the virus would adopt complex regulatory mechanisms to affect the behavior and performance of vector insects directly or indirectly in order to promote its own transmission.PVY is mainly spread by Myzus persicae and other effective vectors in the field.It is important to analyze the variations of aphids behavior in healthy and PVY-infected plants for clarifying the field transmission mechanism of PVY and formulating effective prevention and control measures.However,,the difference in the effects of plant viruses on the behavior of insects at different times of infection in host plants is not clear until now.In this study,PVY,tobacco plants,and aphids as research objects,a variety of experimental methods were used to analyze the effects of different stages of PVY infection on host selection and feeding behavior,growth and reproduction of aphids comprehensively,and compare the difference of the nutrient content as well as gene expression in healthy and PVY-infected tobacco plants.The main findings of this paper are as follows:(1)The probe fluorescence quantitative method was used to determine the spatial and temporal variations of virus particles in tobacco plants after PVY infecting,according to the variations of virus copy number,the replication process was divided into three stages: the early state(3~7 d post-inoculation PVY),the steady state(8~18 d post-inoculation PVY)and the late state(18 d post-inoculation PVY);When PVY infected tobacco systematically,the PVY copy number was different in young and old leaves.The virus particles content in the first and second leaves with fully unfolded was significantly lower than that in the leaves of other parts,while there was no significant difference between the third and eighth leaves.(2)The Y-shaped olfactory apparatus and the electrical penetration graph(EPG)technique were used to compare and analyze the host selection and feeding behavior of aphids in healthy and PVY-infected tobacco plants at different stages.The results showed that PVY-infected tobacco had a significant attraction to aphids than healthy tobacco at the steady state.At the early and steady states,the number of intracellular probing wave(pd)of aphids on infected tobacco was significantly higher than that of healthy plants.At the early and late states,the rate of feeding disturbance wave on infected plants was significantly reduced.(3)The growth and development of aphids on PVY infected tobacco and healthy tobacco were recorded in the life table.The results showed that the fecundity of colonizing aphids on PVY infected tobacco was significantly increased,and the generation of winged aphids was advanced,while there were no significant difference in the growth,development and longevity of aphids.The total contents of soluble sugar and free amino acids,as well as the essential amino acid for the growth and development of aphids were significantly increased in PVY-infected plants at the steady state.(4)Transcriptome sequencing analysis showed that at the steady state of PVY infection,there were2563 genes were differentially expressed significantly,of which 2012 genes were significantly up-regulated and 551 genes were significantly down-regulated.Enrichment analysis showed that there were 15 pathways closely related to volatile secondary metabolites,indicating that PVY could induce the change of volatile compounds in tobacco.In conclusion,the regulatory effect of PVY infection on aphid behavior was stage-dependent,and the changes of the host selection behavior,feeding behavior,fecundity at the steady state and the difference of the wing type differentiation at the late steady of PVY infection were conducive to the transmission of the virus itself.The results provide a theoretical basis for further understanding the interaction among aphids,PVY and tobacco,as well as the prevention and treatment of aphid-borne plant viruses such as PVY.