Facultative Endosymbiont Detection And Motochodrial Gene Polymorphism Of The Bird Cherry-oat Aphid, Rhopalosiphum Padi

The bird cherry-oat aphid, Rhopalosiphum padi, is a notorious pest which damaged thewheat by sap-sucking. This pest can transmit barely yellow dwarf virus, and cause enormouseconomic loss of wheat yield annually in the world. R. padi distributed in the major wheat-growing region of China. The analysis of the facultative endosymbitont diversity and themitochondrial gene ploymorphism not only has a key theoretical significance of bird cherry-oat aphid evolution, but also can provide basic knowledge for the integrated managementcontrol of the pest.We utilized universal primers and specific primers to investigate the diversity offacultative endosymbiont from nine bird cherry-oat aphid filed populations, the resultsshowed that Serratia symbiontica was found in all populations analyzed. Additionally, S.symbiontica was first found in the bird cherry-oat aphid. The phylogenetic tree of S.symbiotica based on16S rRNA showed that the phylogentic relationships had no obviousrelationship to the geographic distance of the R. padi sample locations.The specific primers amplified Wolbachia surface protein (wsp) gene was used to detectthe Wolbachia in the bird cherry-oat aphid. Wolbachia was found in HeZe， ZiBo，HanZhong， WuHan and NanYang populations. However, the infection frequency ofWolbachia varied in different populations, which was accord with the previouslyreported“most-or-few” distribution pattern of Wolbachia. Yet we did not find Hamiltonelladefensa and Regiella insecticola in all the analyzed populations.The mitochondrial COI and Cytb gene of18filed populations was amplified toresearch the mitochondrial gene ploymoephism. The amplified mitochondrial COI and Cytbgene sequence of the bird cherry-oat aphid had no insertion or deletion. The585bp COI genesequence contained13variable sites, and11of which were parsimony information sites andthe remaining two were singleton sites. The666bp Cytb gene sequence had36variable sites,and8of which were parsimony information sites and the remanent28were singleton sites.The combined sequence of COI and Cytb gene was1251bp and included48variable sites,and10of which were parsimony information sites and the remaining38were singleton sites.The general haplotype diversity of mitochondrial COI， Cytb gene and combinedsequence of COI and Cytb gene was0.511,0.647and0.742, respectively. The general nucleotide diversity of COI, Cytb gene and combined sequence of COI and Cytb gene was0.00159,0.00846and0.00161, respectively.There were7,16and20haplotypes for mitochondrial COI, Cytb gene and combinedsequence, respectively. The phylogenetic tree and Network based on the haplotypes of twomitochondrial genes and combined sequence of COI and Cytb gene indicated that thephylogenetic relationship of the haplotypes of the bird cherry-oat had no geographicdistribution pattern.The analysis molecular of variance of the mitochondrial haplotypes suggested thegenetic variation of the bird cherry-oat aphid mainly originated from the differentiation withinpopulations.