Abstract: The internal gut of insects is a complex micro-ecosystem, in which inhabits a large and varied microbial community. This microbial community plays an important role for their hosts’ growth, development, digestion and absorption of nutrition, colonization resistance against invasion of exotic microbes. In this paper, the diversity of bacterial flora of citrus psyllids (Diaphorina citri), which is a vector of the Huanglongbing pathogen Candidatus Liberibacter asiaticus, was investigated based on analysis of 16S rDNA sequences by restriction fragment length polymorphism (RFLP) and denaturing gradient gel electrophoresis (DGGE). The PCR-RFLP result showed that 31 sequences share high homology with Proteobacteria, including Pseudomonadaceae, Enterobacteriaceae, Xanthomonadaceae, Burkholderiaceae, Rickettsiaceae and Rhizobiaceae. The dominant bacterial flora in D. citri included syncytium endosymbiont (5 sequences, homology 99%, isolating frequency 31%), Mycetocyte endosymbiont and Candidatus Carsonella ruddii (5 sequences, homology 98% and isolating frequency 31%), Candidatus Liberibacter asiaticus and Wolbachia. The analysis of 16S rDNA V3 region sequencing by PCR-DGGE revealed that the inner bacteria of D. citri collected from Murraya paniculata were clustered in one branch and those from citrus were clustered in another branch, suggesting that the host plant has more obvious impact on the bacteria flora of D. citri than the geographic location. The sequencing of the isolated bands of DGGE and GenBank alignment showed that the bacteria of D. citri mainly belong to Proteobacteria and Firmicutes, including Pseudomonadaceae, Rickettsiaceae, Enterobacteriaceae, Xanthomonadaceae, Streptococcaceae and Bacillaceae. Syncytium endosymbiont (band 3-4) may be predominating population because it can be stably isolated from D. citri no matter what the host plant is and where the geographic location. The high isolation rate of Wolbachia inside of citrus psyllids revealed that D. citri being infected with Wolbachia is a common phenomenon in China. Both PCR-RFLP and DGGE analysis indicated that the syncytium endosymbiont of D. citri is a dominant bacterial flora and the two methods in combination can reveal the microbial diversity in D. citri conveniently.

Key words:  Diaphorina citri, endosymbiont bacteria, 16S rDNA, microbial diversity, PCR-DGGE, RFLP