| Tomato Yellow Leaf curl Virus Disease (TYLCVD) is a virus disease threatening tomato (Lycopersicon esculentum Mill) production. Currently, TYLCVD has become one of the major diseases that restrict tomato production in Jiangsu province. TYLCVD is caused by Tomato Yellow Leaf Curl Virus (TYLCV)(Geminiviridae, Begomovirus) which is transmitted by the whitefly Bemisia tabaci under natural conditions and survives both in whiteflies and tomato plants. According to previous reports, rapid increase of B. tabaci populations will cause outbreaks of TYLCVD immediately. B. tabaci has a very wide host range, which leads to great difficulties in prevention and control of TYLCVD.In this study, to obtain the best control methods of TYLCVD, on one hand, we used several methods such as insect nets, mulching film, cucumber intercropping, to acquire control effect on the number of B. tabaci populations and the occurrence of TYLCVD explored. Sensitivity of B. tabaci to five pesticides was investigated by using chemical control methods. In addition, resistance-related genes CYP6CM1and Coel in B. tabaci was detected after pesticide treatment72h, and used for reference; on the other hand, we compared the changes of resistant related gene (LeHT1, Permease) expression in resistant and susceptible, and analysised relations to TYLCVD resistance. These assist resistant genes selected to guid breeding work.The results are shown as follows:1. The number of B. tabaci populations in treatment group covered by insect nets was38.22%less than that in uncovered treatment group, suggesting that the insect nets had control effects on the activity of B. tabaci. The number of B. tabaci populations in treatment group covered by black-white and silverblack mulching film was72.57%,50.59%respectively. Incidence rate of covered by insectnets under black-white mulching film35.49%less than that uncovered.Cucumber intercropping had shown no significant effects on the number of B. tabaci populations, but it was advantageous to decrease the occurrence of TYLCVD. The incidence of TYLCVD in treatment group covered by black-white mulching film was by a minimum of7.05%, but covered by black mulching film up to17.64%.The order of major factors affecting the occurrence of TYLCVD was insect nets, mulching film and cucumber intercropping; the best combination was to cover insect nets, black-white mulching film and cucumber intercropping. The number of B. tabaci populations in treatment group covered by UV-film was37.64%less than that covered by ordinary PVC film. Incidence rate was the minimum in fields covered by silver-black mulching film, which was only9.85%. The results showed that black-white and silver-black mulching film had better control effects on the number of B. tabaci populations and the disease. According to the statistical results, the number of B. tabaci populations collected by yellow sticky traps had reached the maximum after trapping for2-9d, number of trapped B. tabaci populations was the largest in treatment group covered by black mulching film, followed by uncovered, transparent film, silver black and black-white mulching film.2. After pesticide treatment for72h, corrected mortality rate of B. tabaci from high to low was:4%Abamectin,98.01%;70%Confidor,80.91%;5%Regent,61.15%;2.5%Lambda-cyhalothrin,40.73%;25%Buprofezin, as lower than5%. Results of semi-quantitive PCR detection showed that, after treated with70%Confidor for72h, expression of CYP6CM1gene in B. tabaci had significantly increased, while expression of Coel gene hadn’t significantly varied, compared with that before pesticide treatment; after treated with4%Abamectin for72h, expression of CYP6CM1gene in B. tabaci was significantly reduced, while no significant difference was observed in expression of Coel gene compared with that before pesticide treatment; after treated with2.5%Lambda-cyhalothrin for72h, expression of CYP6CM1gene hadn’t varied greatly, while that of Coel gene had increased slightly:after treated with25%Buprofezin for72h, a slight increase was observed in the expression of CYP6CM1gene, while that of Coel gene had decreased slightly.3. TYLCV was detected in susceptible(S) and resistsnt TY-2(contains Ty-2resistant gene) on the2day after inoculation (dai), and it was detected in TY-1and TY-3(respectively contains Ty-1and Ty-3resistant gene) on the3and15dai, respectively. Typical symptoms of TYLCVD were observed in S and TY-1on the7and20dai, respectively, while no symptom was observed in TY-2and TY-3during the whole growth period. After inoculation, no expression of LeHT1in S was observed on the0dai, while the expression had increased at first and then declined with the extension of inoculation time; expression of LeHTI in TY-2and TY-3was the highest on the0dai and had decreased with the extension of inoculation time, while that in TY-1had decreased to the minimum after5dai, and then increased slightly; expression of Permease in S had significantly increased after inoculation and slightly declined after7dai, while it had declined in TY-1firstly and then increased after15dai; expression of Permease in TY-2had increased after inoculation, while in TY-3the expression of Permease hadn’t varied greatly and had slightly increased after15dai. Our studies demonstrated that TY-3and TY-2had shown better resistance to TYLCV than TY-1. The expression patterns of LeHTI and Permease gene were different among various lines after inoculation. These indicate that they maybe contain divergent resistant signal pathway and the resistant mechanism among them. |
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