Genetic Diversity Analysis Of 16S RRNA,12S RRNA And Cyt B Gene Among Oxya Chinensis And Oxya Japonica

Oxya chinensis and Oxya japonica are two closely related sepcies in Oxya (Orthoptera, Locustidae, Catantopidae), and morphology and habits are similar in these two species. They are distributed widely in major rice-growing areas in China, and cause serious damage of crops including rice, water bamboo, and corn by feeding on their leaves. Resarches on genetic differences between these two species have important role in revealing genetic relationship of these two species, and are also helpful for their management. However, there is very little study in this aspect at the momment.In this thesis, DNA of five populations of O. chinensis and four populations of O. japonica were extracted and amplified by PCR using primers of 16S rRNA,12S rRNA, and Cyt b genes. DNA products of PCR were sequenced, and base composition, base substitution, base substitution saturability, and genetic distance of these three partial genes were examined. Genetic relationships between these two species, and different population within same species were analyzed by comparing their DNA sequence. Consistencies between these three genes were analyzed using mathematical models, and phylogenetic trees of different populations of these two species were built using ML, NJ, UPMGA, ME methods. Major results were as follows:(1) Average content of A, T, C, G in 16S rRNA partial gene of O. chinensis and O. japonica were 38.9%,31.6%,17.1%,12.4%, and 38.6%,32.2%,17.4%,11.8%, respectively, and total content of A+T were 70.5% and 70.8%, respectively. Average content of A, T, C, G in 12S rRNA partial gene of O. chinensis and O. japonica were 32.1%,41.4%,16.9%,9.6%, and 30.7%,41.6%,17.6%,11.0%, respectively, and total content of A+T were 73.5% and 72.3%, respectively. Average content of A, T, C, G in Cyt b partial gene of O. chinensis and O. japonica were 40.30%,33.5%,10.6%, 15.5%, and 39.9%,32.1%,2.0%,15.9%, respectively, and total content of A+T were 73.8% and 72.0%, respectively. These results were in line with the obvious bias characteristic of A+T bases in mitochondrial genes.(2) Statistics analysis of 16S rRNA genes showed that base conversion value was 12, base transversion value was 8, R value was 1.53, and the most active site of displacement of bases were in the first and third codon positions. Statistics analysis of 12S rRNA genes showed that base conversion value was 9, base transversion value was 3, R value was 2.80, and the most active site of displacement of bases were in the first and third codon positions. Statistics analysis of Cyt b genes by MEGA6 showed that base conversion value was 22, base transversion value was 8, R value was 2.81, and the most active site of displacement of bases were in the first codon position.(3) Base substitution saturability was analyzed by using genetic distance (p) as the abscissa, and Ts and Tv as the ordinate. Results showed that Ts value were greater than Tv in all of 16S rRNA,12S rRNA, Cyt b partial genes, and both of the Ts and Tv were increased linearly with genetic distance. These results indicated that sequence these there partial genes were not saturated in replacement.(4) According to Kimura double parameter model, genetic distance between different populations of these two species were analyzed based on 16S rRNA part,12 s rRNA, Cyt b gene sequence. Results showed that genetic distance between different populations within the same species was very small, and genetic distance between different species was big.(5) According to the LID test of combined data of 16S rRNA,12S rRNA, Cyt b genes, P value was 0.51, which was far more than the threshold value of 0.05. According to the PHT test of combined data of 16S rRNA,12S rRNA, Cyt b genes, P value was 0.4, which was also far more than the threshold value of 0.05. Thses results showed that 12S rRNA & 16S rRNA & Cyt b joint data set was suitable for the joint establishment.(6) Analyzed by ML, NJ, UPMGA, ME methods, phylogenetic trees were constructed using data from each of 16S rRNA,12S rRNA, Cyt b fragments, or joint data set of these three genes. Results showed that there was a general consistence in different phylogenetic trees although a little difference existed between trees, which indicated that the genetic difference between O. chinensis and O. japonica was obvious, and there was a small difference in different geographical populations of O. chinensis, without showing any correlation with geographical distance. For the O. japonica, genetic distance between Wuhan, Jinan, and Harbin populations were small, and genetic distance between Hainan populatin and other population was relatively large.