Isolation of facultative anaerobic entophytic bacterial companioned Ca Las infected citrus tissues and evaluation of dominant bacterial populations
亚洲韧皮杆菌兼性厌氧型伴生细菌鉴定及优势菌群分析

To analysis the entophytic bacterial diversity of citrus and find the companion bacteria populations associated with Huanglongbing pathogen-infected and healthy citrus plant tissues for decipher the co-cultivation of HLB pathogen, we selected varied parts of citrus tissues collected from different loca-tions of citrus planted area. The facultative anaerobic entophytic bacteria were isolated and purified based on bacterial morphology, physiology, biochemistry characteristics and the molecular method of PCR-DGGE (Denaturing gradient gel electrophoresis) analysis based on the sequence of 16S rRNA V6-V8 fragment gene. By the directional isolation of the facultative anaerobic entophytic bacteria and 16S rDNA amplification, total 12 genera of bacteria were identified from 19 cultivable bacterial popula-tions. The dominant bacterial population in infected citrus plants were Curtobacterium sp. (IF: 29.07%), Bacillus sp. (IF: 23.12%), Microbacterium sp. (IF: 21.09%) while in healthy citrus tissues belonged to Bacillus sp. (IF: 21.03%), Planococcus sp. (IF: 20.69%), Pseudomonas sp. (IF: 17.44%). From 50 target bands obtainded by the DGGE approach, 9 genera of cultivable bacteria were recognized. The dominant bacterium population belonged to Serratia sp. (IF: 28%) and Pantoea sp. (IF: 14%) followed by it. Can-didatus Liberibacter asiaticus was only found in tangerine pith of deformed orange fruit, which sug-gested that the content (>1%) of Huanglongbing was more in diseased fruits and other tissues of citrus had low abundance percentage. The density and species of entophytic bacteria were also observed in re-markable difference between infected and healthy citrus plant from the PCR-DGGE profiles.