Characterization and etiology of the bacteria associated with huanglongbing
Diva do Carmo Teixeira, Nelson Arno Wulff, Sílvio Aparecido Lopes, Pedro Takao Yamamoto, Marcelo Pedreira de Miranda, Marcel Belatto Spósito, José Belasque Júnior & Renato Beozzo Bassanezi
Due to its destructive nature and fast dissemination pattern by an insect vector, huanglongbing (HLB) is considered the most threatening citrus disease. The discovery of the associated agents was made possible due to the technological advancements obtained in Biology. We know today that HLB is associated to bacteria that grow specifically in the plant phloem and not in culture media. In the 1990s, through the use of molecular techniques, the HLB bacteria were characterized as members of the alpha-proteobacteria and designated Candidatus Liberibacter africanus and Candidatus Liberibacter asiaticus. In 2004, a third species was characterized, Candidatus Liberibacter americanus. Recently, HLB was reported in Brazil (2004), United States of America (2005), Cuba (2007), Dominican Republic (2008), Mexico, Belize, Jamaica and Puerto Rico (2009). 16S ribosomal DNA, intergenic 16SrDNA-23SrDNA regions, in addition to genes of rplKAJL-rpoBC operon were used in phylogenetic analysis, allowing the positioning of liberibacters in relation to other known bacteria. Gene sequences also allowed the development of PCR protocols for bacteria detection and disease diagnosis. This review aims to inform about the importance of the researches on biology and etiology, since they are the basis of the necessary knowledge for the appropriate management in the fight against this citrus disease.