|De Bac, G.|
|Yokomi, Raymond - Ray|
Submitted to: Plant Disease
Publication Type: Research Notes
Publication Acceptance Date: 1/8/2010
Publication Date: 3/5/2010
Citation: De Bac, G., Saponari, M., Loconsole, G., Martelli, G., Yokomi, R.K., Catalano, L., Breithaupt, J. 2010. First Report of “Candidatus Liberibacter asiaticus” Associated with Huanglongbing in Ethiopia. Plant Disease 94(4):482. Interpretive Summary:
Technical Abstract: Huanglongbing (HLB) is the most serious disease of citrus worldwide. Three different “Candidatus Liberibacter” species are associated with HLB: “Ca. Liberibacter asiaticus” (Las), “Ca. L. africanus” (Laf), and “Ca. L. americanus” (1). In Africa, Laf and its vector Trioza erytreae are reported in South Africa, Zimbabwe, Malawi, Burundi, Kenya, Somalia, Ethiopia, Cameroon and Madagascar. Laf and T. erytreae are both heat-sensitive and occur in citrus when temperatures remain below 30-32°C. Inspection of citrus budwood trees in a government nursery and trees in commercial orchards in Tigray and North Wollo (north Ethiopia), revealed some trees showing symptoms of leaf yellowing, desiccated branches and decreased fruit quality and yields. Two symptomatic sweet orange plants were sampled and DNA was extracted from 200mg of desiccated leaf midribs using the CTAB method. This DNA was used as template for real-time (q) PCR and for conventional PCR using the primers A2/J5 that amplify the ribosomal protein gene in the rplKAJL-rpoBC operon of both Laf and Las. Both assays confirmed the samples were infected by Las but not Laf. The PCR amplicons of 703 bp were purified, cloned and sequenced. BLAST analysis revealed that the ribosomal protein sequences (GQ890155 and GQ890156) shared 100% of identity with each other, and 99% of Las identified in Brazil (DQ471904), Cuba (FJ394022), China (DQ157277) and India (AY266352). To our knowledge, this is the first report of Las in Africa, and specifically in Ethiopia. The presence of Las is a threat for warmer citrus-growing areas which are less favorable for Laf and T. erytreae. In areas where Las was confirmed, symptomatic trees were promptly eradicated. More investigations on the spread of Las and surveys for its vectors, especially Diaphorina citri, are necessary.