Huanglongbing (HLB) is a serious disease of Citrus sp. worldwide. in Africa and the Mascarene islands, a similar disease is known as African citrus greening (AcG) and is associated with the bacterium Candidatus Liberibacter africanus (Laf). in recent years, Candidatus Liberibacter asiaticus (Las) associated with the severe HLB has been reported in ethiopia. thus, we aimed to identify the Liberibacter species affecting citrus, the associated vectors in Eastern Africa and their ecological distribution. We assessed the presence of generic Liberibacter in symptomatic leaf samples by quantitative PCR. Subsequently, we sequenced the 50 S ribosomal protein L10 (rplJ) gene region in samples positive for Liberibacters and identified the species by comparison with public sequence data using phylogenetic reconstruction and genetic distances. We detected generic Liberibacter in 26%, 21% and 66% of plants tested from Uganda, Ethiopia and Kenya, respectively. The rplJ sequences revealed the most prevalent Liberibacters in Uganda and Ethiopia were LafCl (22%) and Las (17%), respectively. We detected Las in Kenya for the first time from three sites in the coastal region. Finally, we modelled the potential habitat suitability of Las in eastern Africa using Maxent. the projection showed large areas of suitability for the pathogen in the three countries surveyed. Moreover, the potential distribution in Eastern Africa covered important citrus-producing parts of Ethiopia, Kenya, Uganda and Tanzania, and included regions where the disease has not been reported. These findings will guide in the development of an integrated pest management strategy to AcG/HLB management in Africa. Huanglongbing (HLB) is presently one of the most destructive plant diseases affecting citrus groves worldwide 1. The disease is associated with Candidatus Liberibacter asiaticus (Las) and Candidatus Liberibacter americanus (Lam), which are phloem-limited, fastidious, gram-negative bacteria belonging to the alpha subdivision of Proteobacteria 2,3. Las is heat-tolerant and associated with the severe HLB which is transmitted by the Asian citrus psyllid Diaphorina citri Kuwayama (Liviidae) 4. Diaphorina citri is distributed in Asia, the United States, Central America, Ethiopia and Brazil 5-10. In addition to Las and Lam, the citrus-infecting Liberibacter genus contains another species: Candidatus Liberibacter africanus (Laf) 1. Laf is heat-sensitive and is associated with African citrus greening disease (ACG) 11-13. This pathogen is principally transmitted by Trioza erytreae (Del Guercio) (Triozidae), also known as the African citrus triozid 14,15. Additionally, several subspecies of Laf have been reported, including Candidatus Liberibacter subsp. capensis (LafC), Candidatus Liberibacter africanus subsp.

Diaphorina citri Kuwayama, also known as the Asian citrus psyllid, is a pest of citrus known for its transmission of Candidatus Liberibacter asiaticus (Ca. L. asiaticus), the causal bacterium of Huanglongbing. The African citrus triozid Trioza erytreae (Del Guercio) (Hemiptera: Triozidae) has been the putative vector of Candidatus Liberibacter africanus (Ca. L. africanus) which causes the African citrus greening disease, until the recent detection of D. citri on the continent. Following reports of D. citri in Kenya and Tanzania, we surveyed citrus plants to establish the presence/absence of D. citri in Ethiopia in citrus-growing regions ranging from 900 to 2,460 m above sea level (masl). Diaphorina citri adults were detected in five of the surveyed sites in Ethiopia. Adult insects encountered were collected using an aspirator and stored in 97% ethanol. The mitochondrial cytochrome oxidase 1 (mt COI) gene of the collected insects was amplified using LepF1/LepR1 primers, and sequences obtained showed low variation, which fell within the acceptable range of species. BLAST was used to query the sequences obtained, and all the sequences linked to D. citri accessions that are available in GenBank. The analysis of the sequences revealed a new haplotype of the species that differs from haplotypes previously reported. Phylogenetic relationships of our samples and other D. citri reference sequences was inferred using the Maximum-likelihood method. Monophyly was observed between the samples and the publicly available sequences from global accessions. This is the first report of the presence of D. citri in Ethiopia.