Influence Of Hosts On Population Of Myzus Persicae (Sulzer) And Coat Protein Gene Sequence Analysis Of TuMV, TMV And CMV In Chongqing

Recently, Myzus persicae (Sulzer) and tobacco mosaic diseases, the most main pest and diseases, appeared on tobacco and have caused tremendous economic losses on the production of tobacco. Influence of three hosts on development, survival and reproduction of Myzus persicae (Sulzer). RT-PCR was used to clone the coat protein (CP) genes of TuMV-CQ, TMV-CQ and CMV-CQ. Meanwhile, these six coat protein genes were sequenced and compared with other homologous sequences in GenBank. This thesis provides some reliable technique and theory for controlling Myzus persicae (Sulzer) and tobacco diseases spreading and harming. At the same time, the results will be helpful to construct faster molecular and serological methods and study on strains of TuMV, TMV and CMV.The main results of this thesis are as follows:1 Influence of different hosts on development, survival and reproduction of Myzus persicae (Sulzer)The effects of host plants and host infected TuMV on development and reproduction of Myzus persicae (Sulzer) were studied under the condition of 25±0.5℃, RH 75%±5%, L:D=14:10. The results showed that there were obvious difference in the development and reproduction of Myzus persicae (Sulzer). On Brassica chinensis (Linn.), the duration of nymph was shortest (5.6929d), fecundity was biggest (34.4386), and the date of maximum mortality was latest among these three hosts. The innate capacities of population increase (r_m) of three hosts were given in the order: Brassica chinensis (Linn.) (0.2681)＞cabbage (0.2572)＞tobacco (0.2271). According to the parameters of life table, we inferred that the most suitable host of Myzus persicae (Sulzer) is Brassica chinensis (Linn.), but the most unsuitable host is tobacco in the above three hosts.In these three hosts infected TuMV, the fecundity of Myzus persicae (Sulzer) on tobacco (21.4727) and cabbage (21.4143) were significantly higher than those on Brassica chinensis (Linn.). On the date of maximum fecundity, the order of fecundity of Myzus persicae (Sulzer) on three hosts infected TuMV is cabbage (4.0455)＞tobacco (2.7647)＞Brassica chinensis (Linn.) (1.6508). The date of maximum fecundity on tobacco and cabbage were 11, but on Brassica chinensis (Linn.) was 14. The innate capacities of population increase (r_m) of three hosts infected TuMV were given in the order: cabbage(0.2556)＞tobacco (0.2158)＞Brassica chinensis (Linn.)(0.1729). The result showed that the influence of Brassica chinensis (Linn.) infected by virus on the population was biggest, but the cabbage was smallest.By comparison of healthy tobacco, the survival rate of nymph and the reproduction of adult on three hosts infected TuMV were lower. The values C of Weibull model for the population survival rate of aphid were all greater than 1 on different healthy and infected hosts. So the survival rate of nymph all belonged toⅠtype. The c value of the survival rate on cabbage was biggest, but on tobacco was smallest. Dates of maximum mortality of aphid on tobacco and cabbage infected TuMV were earlier than on healthy hosts, but on infected Brassica chinensis (Linn.) was later. The result showed that the duration of nymph on infected cabbage was longer, duration of adult was shorter, and reproduction was reduced. On infected Brassica chinensis (Linn.), the duration of nymph was significantly higher than on healthy hosts, and the reproduction was also reduced. There was no significant difference on the duration of nymph and adult, and the reproduction between healthy and infected tobacco. These suggested that comparison of healthy hosts, the influence of Brassica chinensis (Linn.) infected by virus on the population was biggest, but the tobacco was smallest.2 Coat protein gene sequence analysis of TuMV, TMV and CMV in ChongqingThe integrated and pure RNA was obtained from a bit of infected tobacco leaves. The CP gene of these three viruses from Chongqing was amplified by reverse-transcriptase polymerase chain reaction (RT-PCR) and it was cloned and sequenced. Then sequence homology was analyzed and the phylogenetic tree was built.Comparison of the nucleotide and amino acid sequences of TuMV-CQ with the corresponding sequences of several TuMV isolates on Genebank showed that the homology are 86.1%～99.6% at nucleotide level, and 92.3%～99.0% at amino acid level. TuMV-CQ shares 99.6 % and 99.0% homologies at the nucleotide and deduced amino acid levels, respectively, with the strain TU7. The result showed that TuMV-CQ could belong to group world-B.Compared with the corresponding sequences of TMV isolates, the homology of TMV-CQ are 71.9%～99.8% at nucleotide level, and 78.5%～100.0% at amino acid level. TMV-CQ shares 99.8% and 100.0% at the nucleotide and deduced amino acid levels, with one of the Yunnan strain, indicating that they could belong to the same strain.Comparison of the nucleotide and amino acid sequences of CMV-CQ with the corresponding sequences of several CMVⅠisolates showed that the homology are 89.8%～99.5% at nucleotide level, and 91.9%～98.6% at amino acid level, on the other hand, it were 75.1%～76.7% at nucleotide level, and 77.5%～80.2% at amino acid level with the strains of CMVⅡ, which suggested that the CMV-CQ belongs to CMVⅠother than CMVⅡ.