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Search Results: 1 - 10 of 2311 matches for " Candidatus Liberibacter spp "
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Presencia de Diaphorina citri (Hemiptera: Psyllidae) en el Noroeste Argentino (NOA)
Augier,Lucrecia; Gastaminza,Gerardo; Lizondo,Marcelo; Arga?araz,Manuel; Willink,Eduardo;
Revista de la Sociedad Entomol?3gica Argentina , 2006,
Abstract: the distribution of diaphorina citri kuwayama (hemiptera: psyllidae) is expanded to north west argentina.
Presencia de Diaphorina citri (Hemiptera: Psyllidae) en el Noroeste Argentino (NOA) Record of Diaphorina citri (Hemiptera: Psyllidae) in North West Argentina
Lucrecia Augier,Gerardo Gastaminza,Marcelo Lizondo,Manuel Arga?araz
Revista de la Sociedad Entomol?3gica Argentina , 2006,
Abstract: Se amplía la distribución de Diaphorina citri Kuwayama (Hemiptera: Psyllidae) para el Noroeste Argentino. The distribution of Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is expanded to North West Argentina.
Quantitative Screening of Secretory Protein Genes in Candidatus Liberibacter Asiaticus  [PDF]
Binbin Li, Yi Yang, Zhiwen Luo, Zhixin Liu, Naitong Yu
American Journal of Plant Sciences (AJPS) , 2018, DOI: 10.4236/ajps.2018.912174
Abstract: Huanglongbing (HLB) is the most destructive disease of citrus worldwide. The disease is caused by Candidatus Liberibacter spp., which is vectored by the psyllids Diaphorina citri Kuwayama and Trioza erytreae. Secretory proteins are important in bacterial pathogenesis and structure components. Some of them are expressed at a high level. To obtain the highly-expressed secretory protein genes (SPGs) for antiserum preparation, six candidate SPGs were chosen from Candidatus
Haplotypes of “Candidatus Liberibacter europaeus” also separate by geography and host species
Warrick R Nelson
PeerJ , 2015, DOI: 10.7287/peerj.preprints.649v1
Abstract: “Candidatus Liberibacter europaeus” (Leu) is one of six currently known Liberibacter species. It is known primarily from pear and related species across Europe, and from Scotch broom and its associated psyllids in New Zealand (introduced from Britain). The psyllids were introduced to New Zealand as a biocontrol agent for broom and it is thought the bacterium may have been introduced as an endosymbiont of the psyllids. No symptoms in apple or pear trees have been reported, but mild symptoms can occur in broom. 16S and 16S–23S intergenic spacer region DNA sequences of this species have been deposited in GenBank. Analysis of these sequences and associated ecological descriptions indicates the occurrence of two haplotypes, LeuA and LeuB, defined not only genetically but also by geographic range as well as by plant/psyllid host species composition. Liberibacter species are new to science and haplotype identifications enable historical accounts of relationships and spread to be generated.
PCR detection of Candidatus Liberibacter asiaticus, the agent of Huanglongbin or greening disease in citrus
V.K. BARANWAL*, S. MAZUMDER, JITENDER SINGH, V. SURYANARAYANA, D.K. GHOSH and Y.S. AHLAWAT
Indian Phytopathology , 2012,
Abstract: The causal agent of Huanglongbing (HLB) or citrus greening disease (CGD) was detected from total DNA isolated from midrib of leaves of citrus trees from Delhi, Jammu and Maharashtra showing symptoms of yellowing or yellow mottling by PCR amplification of ribosomal protein gene. The amplicon was cloned in pGEM-T easy vector and sequenced. The clone was 703 nucleotide long and showed 100 % nucleotide sequence identity with part of b operon gene of Asian species of greening bacterium i.e. Candidatus Liberibacter asiaticus but differed from African species of greening bacterium i.e. Candidatus Liberibacter africanus. Our studies indicated that b operon gene of Asian species of greening bacterium is highly conserved and can be used for quick detection of greening bacterium in citrus plant for phytosanitary and certification programme.
Sequence of Anatomical Symptom Observations in Citrus Affected with Huanglongbing Disease
D.S. Achor,E. Etxeberria,N. Wang,S.Y. Folimonova
Plant Pathology Journal , 2010,
Abstract: This study was undertaken to develop a better understanding of the relationship between symptom development and the nature of the citrus disease, huanglongbing. The most characteristic symptom of huanglongbing (HLB) is the non-symmetrical mottled chlorosis of leaf blades. Starch accumulation and phloem collapse have been associated with symptom development in this disease presumed to be caused by Candidatus Liberibacter asiaticus. Several hypotheses regarding phloem disruption to starch accumulation to chlorosis evolved concerning symptom development. These were tested using light and Transmission Electron Microscopy (TEM). Samples collected and fixed for TEM with various stages of HLB symptoms, revealed the following: starch accumulation occurred after phloem plugging and cell collapse and therefore, localized carbohydrate deficiency may be a factor. Starch packing of chloroplasts did not rupture the outer membranes, but the inner grana structure was disrupted thus, leading to chlorosis. This occurred only in parts of the leaf where phloem plugging occurred. Sieve elements were obstructed by both amorphous and filamentous materials and both occurred in readily observed amounts, while bacteria were insufficient to directly cause plugging. The amorphous material was positively identified as callose by immunoassay with gold labeling. Phloem protein 2 was identified in the filamentous plugging material using immunoassay with gold labeling. This information supports the development of HLB symptoms in the following sequence: phloem plugging and necrosis with cell wall swelling of sieve elements and companion cells followed by some phloem cell collapse, presumed sugar backup in localized leaf blade areas leading to starch accumulation until chloroplast structure is disrupted with resulting chlorosis.
PCR Detection and Distribution of Huanglongbing Disease and Psyllid Vectors on Citrus Varieties with Changes in Elevation in Kenya
T. Magomere,Silas D. Obukosia,E. Mutitu,C. Ngichabe
Journal of Biological Sciences , 2009,
Abstract: The current decline in citrus production in Kenya is attributed to a great extent to Huanglongbing (HLB) (greening) disease, caused by Candidatus Liberibacter africanus. The control or eradication of the disease has been seriously impeded by the lack of appropriate disease indexing methods and lack of current information on the distribution of the disease and its vector. The purposes of this study were three-fold: To design a HLB detection method for Kenyan strains, to determine the the impact of variation in altitude and citrus varieties on disease distribution using both morphological and molecular techniques. A PCR detection methodology was designed to amplify the ribosomal protein (rplJL) gene of the Candidatus Liberibacter africanus strains that cause HLB disease in citrus. A 716 -720 bp fragment of the rpL10/rpL12 rDNA was PCR amplified from HLB infected samples while samples obtained from greenhouse maintained citrus had no amplification. The PCR amplification of the rplJL gene provides a precise tool to detect the presence of Candidatus Liberibacter africanus bacteria in citrus in all environments and therefore accurate indexing for the HLB disease before and after symptoms develop on the plant. The HLB disease and its psyllid vectors were found to be most prevalent on Washington navel orange growing in altitudes above 1400 mASL and was least found in the lower midlands (800-1250 mASL). There is need to integrate stringent and early disease detection tools with the use of clean planting material to curb the spread of the disease in the country.
Molecular Study of a New Disease of Peach in Iran Associated with a Phytoplasma  [PDF]
Maryam Ghayeb Zamharir
Advances in Microbiology (AiM) , 2014, DOI: 10.4236/aim.2014.41005
Abstract:

In recent years, a disease has been reported to affect peach trees in Kurdistan province of Iran causing serious losses to the production. Main symptoms of disease include leaf stunting and yellowing, which lead to failure in fruit production at harvest. For diagnosis of disease and identification of the causal agent, symptomatic leaf samples were collected in Kurdistan orchards during summer 2010 and were carried to the laboratory. Total DNA was extracted from plant samples according to the standard procedures and indexed by grafting and nested PCR using phytoplasma generic primers, P1/P7 and R16F2n/R2. PCR products were characterized by RFLP technique and direct sequencing. The 16S rDNA sequences were compared with those of other phytoplasmas in GenBank. Phytoplasma rDNA was amplified from 20 out 35 samples. The 16S rDNA sequences of the phytoplasma were identified in Peach samples which showed 98% similarity to that of Candidatus Phytoplasma phoenicium which is considered to be the causal agent of Almond witches’ broom. Phylogenetic analysis of 16S rDNA sequences placed peach strains in Almond witches broom isolate as a member of pigeon pea witches broom (PPWB) group. Further studies on the epidemiology of Ca. Phytoplasma phoenicium and its vector(s) in Iran are recommended in order to identify new natural hosts and develop successful disease management programs.

Technological Advances in Huanglongbing (HLB) or Citrus Greening Disease Management
Krishna Prasad Paudyal
Journal of Nepal Agricultural Research Council , 2015,
Abstract: Huanglongbing (HLB), previously citrus greening disease, is the most destructive of citrus species causing major threat to the world citrus industry. The disease was reported from China in 1919 and now known to occur in more than 40 different countries of Asia, Africa, South and North America. Three species of gram negative bacterium namely Candidatus Liberibacter asiaticus, Candidatus Liberibacter africanus and Candidatus Liberibacter americanus are the casual organisms of HLB, respectively prevailing in the continent of Asia, Africa and South America. It is one of the most extensively researched subjects in citriculture world. HLB was detected in 2004 and 2005, respectively in San Paulo of Brazil and Florida of USA: the two leading citrus production hub of the world causing huge economic loss within 5 years of first detection. Since then research on HLB detection and management was further accelerated in American continents. This paper presents the scientific advancement made on detection, spread, economic losses caused by HLB in different parts of the world and controlling management strategies. Remarkable achievements have been made on HLB detection techniques including iodine test, qPCR and more recently in spectroscopy. While efforts are being made to develop resistance varieties using conventional and biotechnological tools management strategy which includes reduction of inoculums source, vector control and replant with disease-free planting materials still remains major option for HLB control. Citrus intercropping with guava have shown promising results for vector reduction.
Molecular identification of mango malformation pathogens in Egypt  [PDF]
Wafaa M Haggag, M Hazza, M. M Saker, M. Abd El-Wahab
Advances in Bioscience and Biotechnology (ABB) , 2011, DOI: 10.4236/abb.2011.24033
Abstract: Diagnostic tests by molecular biology is made for studying the relations among Fusarium species for linking production of proteins, degree of relationship and occurrence of malformation. Determination of proteins for isolates causing-disease by SDS-PAGE explained there’s specific band for each fungus and there are common bands among some isolates of fungi. Since, band with MW 30 KDa represented only in F. proliferatum and F. oxysporum and F. subglutinans respectively. This band considered as specific band for these isolates, which released high pathogenisity effect. RAPD–PCR markers were used to discriminate variations between Fusarium isolates and causing disease. There is specific band for each fungus which act as molecular marker for each fungus and there are some bands common among some isolates of pathogenic fungi. The dendrogram shows there is degree of relationship between F. sterilihyphosum and F. proliferatum; between F. moniliforme and F. subglutinans; between F. oxysporum and F. chlamydospore; the degree of relationship among F. subglutinans, F. proliferatum and F. sterilihyphosum and degree of relationship among F. moniliforme, F. sterilihyphosum, F. proliferatum and F. subglutinans
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