Impacts Of Plant Viruses On Imidacloprid Susceptibility Of Vector Bemisia Tabaci

Bemisia tabaci(Hemiptera:Aleyrodidae)is a worldwide invasive pest and vector of plant viruses.It can not only cause direct harm to plants by feeding on plant juice,but also transmits more than 200 plant viruses.Cucurbit chlorotic yellows virus(CCYV)and Tomato yellow leaf curl virus(TYLCV)are two types of plant viruses,which represent two different modes of transmission(semi-persistent and persistent,respectively).As external stimuli,viruses may have a series of effects on their vector insects.To this end,we propose the hypothesis that "the insecticide susceptibility of vectors may be affected by the viruses they carry".The purpose of this study is to verify:(1)Do different types of plant viruses have different effects on susceptibility to different biotypes of B.tabaci?(2)If so,do different types of plant viruses have different effects on susceptibility to different biotypes of B.tabaci?Will it further affect the resistance of B.tabaci?It is expected that the results of this study will help to clarify the interaction between the virus and its vector,B.tabaci,and provide a new idea for the control of insecticide susceptibility of B.tabaci,as well as to provide a theoretical basis for fonnulating more effective control measures for B.tabaci and the plant viruses transmitted by B.tabaci.In this study,biotypes B and Q of B.tabaci and their semi-persistently transmitted CCYV and persistently transmitted TYLCV as well as host plants cucumbers and tomatoes were used as experimental materials.Real-time fluorescent quantitative PCR and agar moisturizing method are used to detect and compare the expression level of CYP6CM1(Gene related to imidacloprid susceptibility in P450 detoxifying enzyme system)and the change of insecticide susceptibility of two biotypes of B.tabaci under different conditions.The main results of this study are as follows:(1)Effect of a single virus on the expression level of CYP6CM1 in B.tabaciThe effect of CCYV on the expression of CYP6CM1 gene in B.tabaci Q and B biotypes was similar within 20 days.The gene expression in two biotypes of B.tabaci carrying CCYV was up-regulated first and then down-regulated compared with the control,and the CYP6CM1 gene expression of both biotypes carrying CCYV was significantly lower than that of healthy B.tabaci at the late stage(20 d)(P<0.05).These results suggest that CCYV can inhibit the expression of CYP6CM1 gene in B.tabaci carrying CCYV for 20 d.Among the two biotypes,CCYV inhibited CYP6CM1 gene expression more strongly in B.tabaci Q biotype than B biotype.The effect of TYLCV on CYP6CM1 gene expression of B.tabaci Q and B biotypes was basically the same within 20 days,showing a trend of up-regulation at first and then down-regulation.The gene expressions of whiteflies carrying TYLCV on 1 d,10 d and 20 d were lower than those of control,but significantly higher than that of control healthy B.tabaci on 5 d(P<0.05).For two biotypes of B.tabaci,TYLCV had greater effect on CYP6CM1 gene expression in B biotype than Q biotype.(2)Effects of two viruses on the expression level of CYP6CM1 in B.tabaciAfter treatment with TYLCV-CCYV,the expression of CYP6CM1 gene in two biotypes of B.tabaci was different within 20 days.For Q biotype,the expression of CYP6CM1 gene in B.tabaci carrying two types of viruses on 1 d,5 d was significantly lower than that in healthy B.tabaci(P<0.05)but higher expression on 10 d and 20 d,while for B biotype,the expression of CYP6CM1 gene in B.tabaci carrying TYLCY-CCYV on 1 d,5 d and 20 d was significantly higher than that in healthy B.tabaci but much lower on 10 d(P<0.05).Between the two biotypes,the effect of the two viruses on Q biotype B.tabaci was greater within 10 d,while on 20 d,the effect of two viruses on B.tabaci B biotype was more significant.(3)Effects of single virus on imidacloprid insecticide susceptibility of B.tabaciThe effects of CCYV on the susceptibility of different biotypes of B.tabaci to imidacloprid were different at 1 and 10 d.The susceptibility of B.tabaci B biotype after carrying CCYV virus for 1 d and 10 d to imidacloprid was weaker than that of control healthy B.tabaci,reaching a significant level at 10 d(P<0.05),while susceptibility of B.tabaci Q biotype was enhanced to some extent,but there was no significant difference(P>0.05).The effects of TYLCV on the susceptibility of two biotypes of B.tabaci to imidacloprid were also different on 1 d and 10 d.The specific manifestation was that the susceptibility of B biotype was stronger than that of control on 1 d,weakened on 10 d,and the there no much difference between whiteflies carrying the TYLCV and the control whiteflies in Q biotype.(4)Effects of two viruses on imidacloprid insecticide susceptibility of B.tabaciThe susceptibility of two biotypes of B.tabaci carrying TYLCV-CCYV to imidacloprid was weaker than that of the control on 1 d(P>0.05).The susceptibility of B.tabaci B biotype to imidacloprid increased significantly(P<0.05)and B.tabaci Q biotype to imidacloprid decreased significantly(P<0.05).In conclusion,single virus CCYV or TYLCV could significantly reduce the expression level of CYP6CM1 gene in B.tabaci after 20 days of infection.At this time,its susceptibility to imidacloprid increased markabley in comparison with that of healthy B.tabaci.In B.tabaci carrying both viruses for 20 days,the expression level of CYP6CM1 gene was significantly increased,while its susceptibility to imidacloprid became lower than that of healthy B.tabaci.Therefore,the effects of different viruses on the expression level of CYP6CM1 gene and thesusceptibility to imidacloprid are different,and the newly carried virus can change the influence effects of the pre-carred virus on insecticide susceptibility in B.tabaci to a certain extent.