| Tobacco is an important economic crop in Chongqing. The widespread of Tobacco mosaic disease in tobacco production has brought the huge economic losses to the tobacco quality and yield, and thus seriously constrains the development of the tobacco industry in Chongqing. Tobacco mosaic virus disease was caused by tobacco mosaic virus (TMV), cucumber mosaic virus (CMV), and potato virus Y (PVY) alone or mixed, which was non-persistent transmitted by Myzus persicae,(Sulzer) in the field. At present, TuMV have shown the spread trends in field year by year. With the complex field symptoms and serious damage to tobacco, TuMV has become a new virus disease on tobacco crops. TuMV mainly infects cruciferous crops, while until now there is no research about whether the existence of TuMV mutations in the infection to tobacco and the changes of aphids transmission ability. In current study, we focused on Turnip mosaic virus and its vector M. persicae, comparatively studied the the tobacco mosaic virus types, the winged aphids dynamic relationship with the tobacco mosaic disease, the virus transmission ability of aphids to infect tobacco, TuMV coat protein (CP) gene sequence differences on radish, the transmission abilities to spread tobacco TuMV on different experimental populations in Chongqing though the knowledge of Media entomology and techniques of molecular biology. Our results provide important information to the mechanism of non-persistent virus for aphid transmission, and the comprehensive management of tobacco TuMV. In this thesis the main findings are as follows:1The relation between the Wulong winged aphids dynamic and tobacco mosaic virus diseaseAccording to yellow board trap results, we found that the trap winged aphids were mainly four species, namely, the tobacco aphid, turnip aphid, soybean aphid and cotton aphid in the Wulong tobacco field, in addition, we also identified that M. persicae was the largest proportion wingless aphid in tobacco plants, which suggests that M. persicae can colonize on the tobacco. The close relationship was found between tobacco mosaic virus disease and the dynamic of winged aphids, the survey in the field informed that the virus disease occurred in the early mid-July, reached in a peak in the middle July and stabilized in end of July and early August. Winged aphids moved in tobacco fields of the peak in mid-July, coupled with the tobacco mosaic virus disease incubation period, suggested that the occurrence of virus diseases and the increase in the number of winged aphids was consistant.2. Detection and identification of the tobacco mosaic virusWe randomly selected24samples to more than100tobacco total samples collected from Wulong, and determined by indirect. ELISA results which showed that the24test samples were infected with TMV, CMV, PVY, to TuMV, and100%mixed infection with only significant difference in contents, in which PVY was the highest, followed by TuMV, and CMV was the lowest. In the field of tobacco samples showed complex type of virus disease symptoms, which suggested that mixture infection of tobacco mosaic virus was serious in the field. PVY and TuMV has become the dominant toxic original in China.3. CP gene cloning and sequence analysis of the TuMV infected tobacco and radishTuMV CP gene sequencing results on tobacco and radish showed that the length were986bp and984bp, and encoded amino acids326and307, respectively. We compared the CP nucleotide and amino acid sequences, which showed14point changes in the nucleotide sequence and eight point mutations in the amino acid sequence, but both the CP gene contains the encoding amino acids of DAG motif which was necessary for aphid to transmit the TuMV. The sequences comparison results showed that the nucleotide similarity of the two CP gene sequences cloned in this study was98.6%and96.4%amino acid similarity.4. Study on Myzus persicae (Sulzer) transmission ability to TuMVAphids showed significantly difference about the abilities to transmit TuMV virus on different hosts. When the aphid density was ten per strain, the incidence rate was85.00%after feeding by the aphids with virus, which indicated that aphids in tobacco presented the highest virus transmission abilities among all tested hosts. In addition, only65.00%in radish implied the lower virus transmission ability compared with tobacco. The lowest virus transmission ability was indentified in cabbage with40.00%. The beginning of presenting the virus symptoms was tested, which showed that obacco required the shortest time, and followed by radish, and the longest time recorded in cabbage. These results demonstrated that aphid on tobacco expressed the most the most efficient in transmit the TuMV. In addition, we also tested effect of the density of aphids on host to the virus transmission ability, which showed significnt resutls. The order of transmission abilities is:20=15>10>5>1, and the population density of15and20led to100%infection, with the earliest symptoms occurrence and strongest virus transmission ability. When the aphid density is one, the virus infection was25.00%, with the latest symptoms occurrence and weakest virus transmission ability. |
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