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Analysis of 16S rDNA Sequences from Citrus Huanglongbing Bacteria Reveal a Different “Ca. Liberibacter” Strain Associated with Citrus Disease in São Paulo

August 2005 , Volume 89 , Number  8
Pages  848 - 852

H. D. Coletta-Filho , M. A. Takita , M. L. P. N. Targon , and M. A. Machado , Centro APTA Citros Sylvio Moreira, Instituto Agronômico, CEP 13490-970, CP04, Cordeirópolis SP, Brazil



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Accepted for publication 13 April 2005.
ABSTRACT

Citrus huanglongbing (HLB, ex greening) is one of the most serious and destructive citrus diseases in the world. It is caused by a phloem-limited and nonculturable bacterium, “Candidatus Liberibacter”. The disease occurs in some Asian and African countries and recently has been reported in the state of São Paulo, Brazil. Analysis of the 16S ribosomal (r)DNA of the HLB bacteria from orchards in São Paulo revealed the presence of two distinct strains of “Ca. Liberibacter”. One of them, named LSg1 (Liberibacter sequence group 1), was 100% identical to strains from Japan (GenBank accessions AB038369 and AB008366), the Asian forms of the bacteria. The other, LSg2, is genetically distant from the Asian (96.1 to 96.3% identity) and African (95.8 to 96.1% identity) strains. Comparison of the 16S rDNA sequences from the LSg2 and the Asian strain revealed the presence of INDELs and point mutations. Specific primers designed for this Brazilian Liberibacter strain revealed that it is more widely distributed throughout the São Paulo orchards compared with the LSg1 strain. The HLB symptoms caused by both strains are almost identical and, interestingly, both strains were found in the same sample, revealing mixed infection in a citrus plant.


Additional keywords: PCR, sweet orange

© 2005 The American Phytopathological Society