| Rice water weevil, Lissorhoptrus oryzophilus (Coleoptera: Curculionidae) is animportant rice pest species which invaded in China. The rice water weevil, which isoriginally from America, reproduces majorly through amphigenesis and concurrentlyreproduces parthenogenetically. Nevertheless, only parthenogenesis occurs in all theinvaded regions. Since parthenogenesis is the significant reason why such pest can invadeand massively spread in China. Currently, the rice water weevil has be detected in mostparts of China, such as XinJiang, HeBei, ShanDong, LiaoNing, ZheJiang, JiangXi,HuNan and so on, and it has already spread to the nearby province. Rice water weevil isthe crucial quarantined insect. Wolbachia are a common and widespread group of bacteriafound in reproductive tissues of arthropods. These bacteria are transmitted through thecytoplasm of eggs and have evolved various mechanisms for manipulating reproductionof their host, including induction of reproductive incompatibility, pathenogenesis,feminization, male-killing and so on. This experiment mainly study the WSP,16SrDNAand MLST genes of Wolbachia infected in rice water weevil and other insects. Also, thisstudy does some researches about the horizontal transmission of various rice water weevilgeographic speices by analyzing the gene sequences of16SrDNA, WSP and five MLSTgenes. By using the bioinformatics programs, DNAstar, DNAman, Clustal and Mega, thenucleartide sequence composition, variation frequency were analysed and phyogenic treesfor the respective gene were constructed. The preliminary results of this study could beilluminated as following:1The Wolbachia infection frequencies of different geographic rice water weevilpopulations varied negatively significant, closing to100%. However, the infection rate ofthe other insects are remarkably different from the rate of rice water weevil. Some of themare very high, approximately to100%; some are very low, closing to zero. The Paederusfuscipes curtis and Harmonia axyridis collected from JiangXi provience didn’t detectWolbachia, so the frequency is zero. The results are same to the wolbachia infection rate ofPirata subpiraticus and Ummeliata insecticeps species.2The COI gene phylogenetic tree shows：19rice water weevil populations,collected from China, Korea, Japan and California, were clustered in the same clade. Buttwo other populations collected from original place-America were gathered in anotherclade. It is surprised that there are no difference of the COI sequence between the male andfemale which were collected from Texas. And they are gathered with the CrowleyLouisiana population in another clade based on the COI gene sequence. Albeit thesequences of the two sets of populations have some slight difference, direct evidence stilllacked to prove this point, and it suggested that the difference is nonsignificantly related to the geographic location.3According to the results of N-J phylogenetic tree of WSP gene sequences ofWolbachia, most of the Wolbachia strains are belong to supergroup B, except theWolbachia strains in Pyrrhocoridae, which belongs to supergroup A. Accroding to thephylogenetic tree of Wolbachia WSP gene sequence, the Wolbachia WSP sequences of18L.oryzophilus populations were clustered into the same branch. However, the same genesequences of another3L.oryzophilus adult populations which collected from the originalcountry-America were gathered in other branch. And the WSP sequences of female adultsin texas are identical to this sequence of the male. However, the same gene sequence of theother insect samples which collected from Guizhou and Jiangxi province of China, wereclearly with significant difference to the rice water weevil. Especially, the WSP sequenceof Pyrrhocoridae belongs to supergroup A. The results show this gene sequence of all therest samples are clustered in supergroup B though they may not be in the same subgroup orclade. The Wolbachia strains which was found in Tetragnatha maxillosa and Ischnuraasiatica are belongs to subgroup Con and Pip respectively.4According to the analysis of the gene sequences of16S rDNA, the phylogeneticrelationship of22Lissorhoptrus oryzophilus populations are not significant different to theWSP gene sequences. The22Lissorhoptrus oryzophilus strains are still distributed in twoclades based on the16S phylogentic tree. The Wolbachia strains of four insectspecies(including Ischnura asiatica、Paederus fuscipes curtis、Sogatella furcifera and anunidentified species) are all clustered in supergroup B, but not in the same clade. It’sclearly to know that two Ischnura asiatica Wolbachia strains were in different branches.One strain was clustered with the Paederus fuscipes curtis strain, and the other two strainswere in another clade. It shows that Wolbachia may spread by horizontal transmission inthis species. Since the gene sequences of all the detected rww populations are almostidentical, it indicates that the main transmission model of this species should be verticaltransmission. |
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