Citrus huanglongbing in São Paulo State, Brazil: PCR detection of the 'Candidatus' Liberibacter species associated with the disease.
Symptoms of huanglongbing (HLB), one of the most serious diseases of citrus in Asia and Africa, have been noticed in March 2004 in the Araraquara region of São Paulo State, Brazil. HLB has not been reported previously from America. The causal HLB bacteria, Candidatus Liberibacter africanus in Africa and Candidatus Liberibacter asiaticus in Asia, can be detected in symptomatic citrus leaves by PCR amplification of their 16S rDNA with previously described primers. When this technique was applied to 43 symptomatic leaf samples from the Araraquara region, all PCR reactions were negative. This suggested that a new pathogen, not detected by the above primers, could be involved in HLB in the State of São Paulo. Indeed, by using universal primers for amplification of bacterial 16S rDNA, a new liberibacter species, Candidatus Liberibacter americanus, has recently been identified. Specific primers for PCR amplification of the 16S rDNA of Ca. L. americanus have been selected. Using these primers, the new liberibacter could be detected in 214 symptomatic leaf samples tested. The leaves of two additional samples were infected with Candidatus Liberibacter asiaticus, and two further samples contained both Ca. L. americanus and Ca. L. asiaticus. The samples came from 47 farms in 35 municipalities. The psyllid vector of Ca. L. asiaticus, Diaphorina citri, is established in South, Central, and North America (Florida and Texas). Ca. L. americanus could be detected by PCR in several batches of D. citri psyllids collected on symptomatic sweet orange trees infected with Ca. L. americanus, strongly suggesting that D. citri is the vector of Ca. L. americanus. The results reported here confirm the presence of HLB in the State of São Paulo. Ca. L. americanus is the most widely distributed pathogen.
do Carmo Teixeira
Diva
D
Fundecitrus, Av. Dr. Adhemar Pereira de Barros, 201, CEP 14807-040 Araraquara, SP, Brazil.
Luc Danet
Jean
J
Eveillard
Sandrine
S
Cristina Martins
Elaine
E
de Jesus Junior
Waldir Cintra
WC
Takao Yamamoto
Pedro
P
Aparecido Lopes
Silvio
S
Beozzo Bassanezi
Renato
R
Juliano Ayres
Antonio
A
Saillard
Colette
C
Bové
Joseph Marie
JM
D001483:Base Sequence; D001938:Brazil; D002957:Citrus / Q000382:microbiology*; D004275:DNA, Ribosomal / Q000235:genetics; D004587:Electrophoresis, Agar Gel; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000382:microbiology; D016133:Polymerase Chain Reaction; D012230:Rhizobiaceae / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D012621:Seasons
D004275:DNA, Ribosomal