摘要

Huanglongbing (HLB), is a destructive quarantine disease of citrus transmitted by psyllids and grafting, with which three species of Candidatus Liberibacter (Ca. Liberibacter asiaticus, Ca. Liberibacter africanus and Ca. Liberibacter americanus) are associated. To investigate the diversity of the Ca. Liberibacter asiaticus, the omp genes of 23 Ca. Liberibacter asiaticus isolates with different symptoms from seven provinces in China were assayed by restriction endonucleases TaqI, BclI, ApoI, SspI and EcoRI. Sequence analysis of omp genes showed that the HLB isolates under study shared 99% identity with Ca. Liberibacter asiaticus (AY642159) and 72% identity with Ca. Liberibacter africanus (AY642158). In a phylogenetic tree, Ca. Liberibacter isolates grouped in two major clusters. The 23 isolates under study grouped with the Asian strains. The groups of Ca. Liberibacter asiaticus was distributed in three subgroups depending on their geographical origin. No genetic evidence for a host determinant was found in Ca. Liberibacter asiaticus isolates except the genetic diversity of the geographical origins.