UC Riverside International Organization of Citrus Virologists Conference Proceedings (1957-2010) Title Huanglongbing (Greening) in Vietnam: Detection of Liberobacter asiaticum by DNA-Hybridization with Probe in 2.6 and PCR-Amplification of 16S Ribosomal DNA Publication Date

J Chau, Minh Trung, Ha Minh
1957 Journal International Organization of Citrus Virologists Conference Proceedings   unpublished
Leaf samples were collected from 55 citrus trees from north, central and south Vietnam in January-February 1995, and analyzed by PCR amplification, DNA hybridization and immunofluorescence for the presence of the Huanglongbing (HLB) (greening) liberobacter. Fortyeight of the 55 samples hybridized with probe In 2.6 which is specific for Liberobacter asiaticum. No hybridization was obtained with probe As 1.7, specific for L. africanum. Forty-five of 47 samples analyzed by PCR gave the 1,160 bp
more » ... ave the 1,160 bp amplicons expected from the liberobacter-specific primers used, and on Xbal digestion, the amplicons gave the two restriction fragments (640 bp and 520 bp) specific for L. asiaticum. The combined use of hybridization and PCR amplification was able to detect L. asiaticum in 53 of the 55 samples tested. Fourteen of 48 samples tested gave a positive immunofluorescence reaction with monoclonal antibodies 10A6 as well as 1A5, known to react with certain L. asiaticum serotypes only. Liberobacters were detected by electron microscopy in four samples tested. These samples were also found to be positive for L. asiaticum by hybridization and PCR. Finally, Hamlin sweet orange seedlings graft-inoculated with budwood sticks from four trees, which were later found positive for L. asiaticum by hybridization and PCR, developed symptoms. These results show that HLB is widespread throughout Vietnam. Symptoms of cristacortis, previously unrecorded in Vietnam, were also seen.
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