African Citrus Greening Disease in East Africa: Incidence, Severity, and Distribution Patterns

2019 ◽  
Vol 112 (5) ◽  
pp. 2389-2397 ◽  
Author(s):  
B A Rasowo ◽  
F M Khamis ◽  
S A Mohamed ◽  
I J Ajene ◽  
O F Aidoo ◽  
...  
Keyword(s):  
East Africa ◽  
Distribution Patterns ◽  
Causal Agent ◽  
Citrus Greening ◽  
Citrus Greening Disease ◽  
Early Disease Detection ◽  
Molecular Phylogenetic ◽  
Citrus Production ◽  
Candidatus Liberibacter ◽  
Greening Disease

Abstract African citrus greening disease (ACGD) is considered as one of the major diseases of citrus threatening citrus production in East Africa. Our study aimed for the first time to assess the incidence, severity, and distribution patterns of ACGD in Kenya and Tanzania. In total, 105 citrus orchards were assessed in 13 regions representing low, mid, and high altitude areas. In each backyard and orchard, trees were randomly selected and rated for visual ACGD symptoms; then leaves and insect samples collected for analysis of ‘Candidatus Liberibacter africanus’ (CLaf), the presumptive causal agent of ACGD. Endpoint PCR, sequencing, and molecular phylogenetic tools were employed to confirm the identity of potential circulating pathogens. Incidence and severity of ACGD varied significantly among the different regions. Both Trioza erytreae (Del Guerico) (Hemiptera: Triozidae) and the invasive Asian citrus psyllid vector Diaphorina citri (Kuwayama) (Hemiptera: Liviidae) were found to co-occur in upper and lower midland regions. Molecular characterization identified ‘Candidatus Liberibacter africanus spp. Clausenae’ (CLafCl) as the main causal agent of ACGD in most of the citrus plants and insect samples. No instances of Candidatus Liberibacter asiaticus infection were found. These findings provide valuable insights into understanding and management of ACGD by employing stringent and early disease detection tools to curb the spread of the disease.

scholarly journals 2006 Florida Citrus Pest Management Guide: Huanglongbing (Citrus Greening)

EDIS ◽  
2019 ◽  
Vol 2006 (1) ◽  
Author(s):  
Ronald H. Brlansky ◽  
Kuang-Ren Chung ◽  
Michael E. Rogers
Keyword(s):  
Citrus Greening ◽  
Rapid Decline ◽  
Publication Date ◽  
Citrus Greening Disease ◽  
Bright Yellow ◽  
Citrus Production ◽  
Candidatus Liberibacter ◽  
Greening Disease ◽  
Florida Citrus ◽  
Serious Disease

Huanglongbing (HLB), commonly called citrus greening disease, is caused by the bacterium, Candidatus Liberibacter spp. The name huanglongbing means “yellow dragon” which describes the symptom of a bright yellow shoot that commonly occurs on a sector of infected trees. HLB is a serious disease of citrus because it affects all citrus cultivars and causes rapid decline of trees. This document is PP-225, one of a series of the Plant Pathology Department, UF/IFAS Extension. Original publication date November 2005. PP-225/CG086: 2020–2021 Florida Citrus Production Guide: Huanglongbing (Citrus Greening) (ufl.edu)

scholarly journals Mitochondrial genetic variation reveals phylogeographic structure and cryptic diversity in Trioza erytreae

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Inusa Ajene ◽  
Fathiya M. Khamis ◽  
Gerhard Pietersen ◽  
Barbara van Asch
Keyword(s):  
South Africa ◽  
Citrus Greening ◽  
Phylogeographic Structure ◽  
Citrus Greening Disease ◽  
Trioza Erytreae ◽  
Baseline Information ◽  
Candidatus Liberibacter ◽  
Mitochondrial Sequences ◽  
Greening Disease ◽  
Genetic Clustering

AbstractTrioza erytreae is the main vector for ‘Candidatus Liberibacter africanus’, the causative agent of African Citrus Greening disease. The insect is widespread in Africa, and has recently disseminated to Southwestern Europe. This study aimed at generating reference mitogenome sequences for T. erytreae, as a background for future genetic diversity surveys. Complete mitochondrial sequences of three specimens collected in Ethiopia, Uganda and South Africa were recovered using Ion Torrent technology. The mitogenomes of T. erytreae from Uganda and Ethiopia were highly similar, and distinct from that found in South Africa. The phylogeographic structure of T. erytreae was assessed using genetic clustering and pairwise distances, based on a dataset of public COI sequences recorded as T. erytreae. The dataset revealed ten haplotypes with strong phylogeographic structure in Africa and Europe. Three haplotypes found in Kenya on Clausena anisata belonged to pairs separated by distances as high as 11.2%, and were basal to all other sequences. These results indicate that not all sequences identified as T. erytreae belong to the same species, and that some degree of specificity with different plant hosts is likely to exist. This study provides new baseline information on the diversity of T. erytreae, with potential implications for the epidemiology of African Citrus Greening disease.

scholarly journals First Report of Citrus Greening Disease and Associated Bacterium “Candidatus Liberibacter asiaticus” from Bhutan

Plant Disease ◽  
2003 ◽  
Vol 87 (4) ◽  
pp. 448-448 ◽  
Author(s):  
Y. S. Ahlawat ◽  
V. K. Baranwal ◽  
Thinlay ◽  
Doe Doe ◽  
S. Majumder
Keyword(s):  
Citrus Greening ◽  
Ribosomal Protein Genes ◽  
Candidatus Liberibacter Asiaticus ◽  
African Countries ◽  
First Report ◽  
Citrus Greening Disease ◽  
Pcr Product ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Greening Disease

During July 2002, surveys of mandarin orchards were conducted in Punakha Valley and Wangdue districts of Bhutan. Symptoms of the greening disease were observed in most of the orchard. The incidence of disease was recorded up to 30% in 24 private orchards with more than 5,000 trees total. Affected trees were generally stunted with leaves showing symptoms of mottling. Sometimes, symptoms were seen only on one part of the canopy. The greening disease is caused by a fastidious phloem restricted bacterium, “Candidatus Liberibacter asiaticus” in Asian countries and “Candidatus Liberibacter africanus” in African countries. To confirm the presence of this bacterium causing greening disease in Bhutan, 33 leaf samples were collected from seven locations in Bhutan and stored at -80°C. Petioles and midribs were used for extraction of DNA using DNeasy Plant Mini Kit (Qiagen Gmbh, Hilden, Germany). Polymerase chain reaction (PCR) was initially performed with a sample from Rimchu, Bhutan using primer pair 5′TATAAAGGTTGACCTTTCGAGTTT/5′ACAAAAGCAGAAATAGCACGAACAA previously designed for amplification of ribosomal protein genes of β-operon of two liberibacter species (1). An amplicon of approximately 700 bp was obtained. The size of the PCR product is similar to that amplified from “Candidatus Liberibacter asiaticus”. The amplicon was cloned in pGEM-T easy vector and sequenced. The clone was 703 nt long and showed 100% sequence homology with the corresponding sequence of “Candidatus Liberibacter asiaticus” confirming that “Candidatus Liberibacter asiaticus” is the cause of greening disease in Bhutan. Later, one sample from each location was analyzed and found to be positive to greening. To our knowledge, this is the first report of this bacterium and greening disease in Bhutan, and citrus greening appears to be the main cause of declining citrus in the Punakha Region of Bhutan. Reference: (1) A. Jocquellet et al. Page 363 in: Proc. Conf. Int. Organ. Citrus Virol. 14th. IOCV, Riverside, CA, 2000.

scholarly journals Production of monoclonal antibody against Ompa protein of Candidatus Liberibacter asiaticus causing citrus greening disease

2020 ◽  
Vol 18 (3) ◽  
pp. 529-541
Author(s):  
Ho Thi Thuong ◽  
Nguyen Thi Thom ◽  
Nguyen Thi Tra ◽  
Trinh Thai Vy ◽  
Pham Bich Ngoc ◽  
...  
Keyword(s):  
Strong Interaction ◽  
Research Direction ◽  
Citrus Greening ◽  
Candidatus Liberibacter Asiaticus ◽  
Citrus Greening Disease ◽  
Candidatus Liberibacter ◽  
Liberibacter Asiaticus ◽  
Ompa Protein ◽  
Greening Disease ◽  
Vhh Antibodies

Citrus Greening, also known as HuangLongbing (HLB), is considered one of the most dangerous citrus diseases, and limiting the production of citrus trees all over the world. Production of antibodies against Ompa protein of Candidatus Liberibacter asiaticus (CLas) for detection of citrus greening disease is considered as promising research direction. In this study, for the purpose of producting antibodies against Ompa of CLas, we firstly used the camel VHH antibody library for screening VHH antibodies against Ompa using phage-display technique. Next, phages which had strong interaction with Ompa as shown in ELISA were selected for phagemid isolation and the DNA fragments encoding VHH antibodies were sequenced. The DNA fragment encoding the best VHH antibody was then selected and inserted into the expression vector pET-21a (+), then cloned in Ecoli DH5α strain and expressed in BL21 (DE3) strain. The expression of VHH antibodies against Ompa was optimized at different temperatures with an inductive concentration of 0.1 M IPTG. Anti-Ompa VHH antibodies were purified under denatured conditions then re-folded. The biological activity of the VHH antibody with Ompa antigen was assessed by indirect-ELISA reaction. Results indicated that the VHH antibody had a very strong interaction with the Ompa antigen. This opens up the prospect of applying VHH antibody in the detection of citrus greening disease.

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