关键词: 柑橘, 黄龙病, Candidatus Liberibactor, 序列

Abstract: Huanglongbing (HLB) , previously known as greening disease, is probably the most serious disease in citrus. The presump tive causal agent is believed to be a non-cultured, phloem-restricted α-proteobacterium. Currently, there are three Candidatus L iberibactor spp. associated with citrus Huanglongbing
(HLB) disease, Ca. Liberibactor asiaticus, Ca. L iberibactor africanus and Ca. L iberibactor am ericanus. In this study, a genomic walkingmethod was used to obtain new sequences extended from previously known loci,rplKAJL-rpoBC, 16S/23S rRNA and outermembrane protein (omp) of Ca. Liberibactor asia ticus. In rplKA-JL 2rpoBC locus, 3 218 bp of new sequenceswere obtained at the 5′up stream end and 2 653 bp at the 3′downstream. Totally, fragments about 1 853 bp and 2 459 bp were also acquired from 5′up stream and 3′down
stream of 16S/23S rRNA region, respectively. Similarly, in om p locus, fragment about 4 014 bp were obtained at 5′up stream and 971 bp at 3′ downstream, respectively. Genomic walking app roach was used in this
study, and totally 15 168 bp non-redundancy sequences from asiaticus specieswere obtained. Sequence analy-sis shows that there are two new genes ( suhB and serA) at the rplKAJL-rpoBC gene cluster locus, four new
genes ( transmembrane p rotein gene, cell wall hydrolase p seudogene, 5S ribosomal RNA and tRNA^Met ) extended from the 16S/23S rRNA gene locus and six new genes ( rpsB, tsf, pyrH, frr, cdsA2, cds2) at the omp
locus. These new sequences obtained in this study will facilitate the PCR-based HLB research.

Key words: citrus, Huanglongbing, Candidatus Liberibactor, sequence