Abstract: 【Aim】 To explore the occurrence and interactions of Candidatus Liberibacter asiaticus (CLas) and the main symbiotic bacteria Wolbachia, Carsonella and Profftella in the Asian citrus psyllid, Diaphorina citri across geographic distributions. 【Methods】 During August 2022-August 2023, we collected samples from 20 populations of D. citri across China’s main climatic regions where this species was prevalent. Nested PCR was employed to assess the Huanglongbing (HLB) infection rates of female adults in each population. qPCR was used to analyze the relative abundance of CLas and three symbiotic bacteria (Wolbachia, Carsonella and Profftella) from five populations with relatively high HLB infection rates. Additionally, we screened the differentially expressed genes in the transcriptomes of adult D. citri infected and uninfected with HLB, followed by KEGG pathway enrichment analysis. 【Results】 Female adults of Lingshan and Rongjiang populations of D. citri had the highest HLB infection rates, both reaching 66.67%, and female adults from seven populations (Qiongzhong, Chengmai, Huaning, Yongchun, Hengshan, Mayang, Fengcheng) were not infected with HLB. Altitude significantly influenced the HLB infection rate of D. citri. Precipitation significantly affected the relative abundance of CLas. Latitude, altitude and temperature significantly impacted the relative abundance of specific symbiotic bacteria. HLB infection also influenced the response of symbiotic bacteria to above these environmental factors. Correlation analysis indicated that HLB infection impacted the correlation of relative abundance among symbiotic bacteria of D. citri. Transcriptome analysis revealed that the differentially expressed genes in HLB-infected D. citri were primarily enriched in pathways related to peroxisome, carbon metabolism, and so on, which may be the cause of changes in the interactions of their symbiotic bacteria. 【Conclusion】 This study confirmed the impact of environmental factors on CLas and the main symbiotic bacteria in D. citri. HLB infection of D. citri altered the response of symbiotic bacteria to environmental factors and their interactions, and these alterations were likely closely associated with the regulation of gene expression in the HLB-infected D. citri, providing important references for developing geographically informed integrated management strategies against HLB.

Key words:  Diaphorina citri, geographic distribution, Huanglongbing; Candidatus Liberibacter asiaticus, symbiotic bacteria, environmental factors