Abstract: 【Objective】The objective of this study is to analyze the endophytic bacteria in Diaphorina citri which may affect the pathogenesis of Candidatus Liberibacter asiaticus, and to provide a basis for artificial culture of Ca. L. asiaticus, prevent and control of HLB. 【Method】 The diversity of cultivable endophytic bacteria in different samples of D. citri with or without Ca. L. Asiaticus from different geographical origins were compared by traditional isolation and culture methods. D. citri with and without Ca. L. asiaticus were divided into three parts: the head, thorax and abdomen, respectively. Then V6-V8 area of 16S rDNA were amplified after extracting DNA, the endophytic bacteria in D. citri of with or without HLB pathogen and in different parts of the same carrier state were compared by 16S rDNA-PCR-DGGE. The relative amount in 8 D. citri samples of Bacillus sp., Salmonella sp., Enterobacter sp. and Ca. L. asiaticus was determined, which have different results in traditional isolation and culture methods and PCR-DGGE, using total amount of bacteria as an amount of contrast. Relative amounts of the 3 chosen bacteria and Ca. L. asiaticus, respectively, in every D. citri sample were compared before comparing similarity of the same bacteria in different samples in order to analyze the interaction of the 3 chosen bacteria and Ca. L. asiaticus. 【Result】 Richness of the colony and colony-forming unit of cultivable endophytic bacteria in D. citri with Ca. L. asiaticus were more than in D. citri without Ca. L. asiaticus. Fourteen kinds of bacteria were isolated from D. citri without Ca. L. asiaticus, belonging to 10 genera, such as Bacillus sp.(3), Erwinia sp.(1), Klebsiella sp.(1), Staphylococcus sp.(2), Arthrobacter sp.(1), Pantoea sp.(2), Pectobacterium sp.(1), Salmonella sp.(1), Streptomyces sp.(1), and Massilia brevitalea sp.(1). While only 4 kinds of bacteria were isolated from D. citri with Ca. L. asiaticus, from 3 genera the same as healthy psyllid, such as Bacillus sp., Klebsiella sp., Pectobacterium sp.. B. aerophilus was isolated frequently from D. citri, as a resident flora in D. citri. As the electrophoretogram of 16S rDNA PCR-DGGE revealed, there were significant differences between D. citri with and without Ca. L. asiaticus in the same tissues, but no significant differences were found in different tissues from the same D. citri. Robotic bands No. 10 (Wolbachia sp.), No. 12 (Wolbachia pipientis), No. 13 (Syncytium endosymbiont of Diaphorina citri), No. 14 (Uncultured bacterium), No. 19 (Serratia marcescens), No. 21 and No. 22 (both are Stenotrophomonas maltophilia) were stable in D. citri with and without Ca. L. asiaticus. Enterobacter sp. was one of the dominant endosymbiotic bacteria of D. citri with Ca. L. asiaticus. Wolbachia also was found in D. citri. The results of q-PCR proved that the results of traditional isolation and culture methods and 16S rDNA-PCR-DGGE were correct, and demonstrated that the relative amount of Enterobacter sp. and Ca. L. asiaticus were positive correlation in the 8 chosen samples. 【Conclusion】 Suspected resident flora B. aerophilus was isolated frequently in D. citri. There may be some interactions between the Enterobacter sp. and Ca. L. asiaticus according to the result of q-PCR, which reveals the relative amount of Enterobacter sp. and Ca. L. asiaticus are positive correlation.

Key words: Diaphorina citri , Candidatus Liberibacter asiaticus , endophytic bacteria , isolation and culture , PCR-DGGE