Citrus huanglongbing in Argentina: detection and phylogenetic studies of Candidatus Liberibacter asiaticus

Abstract

Huanglongbling (HLB) is one of the most devastating diseases of citrus trees. In Argentina, Candidatus Liberibacter asiaticus (CLA) –the causal agent of HLB- was detected for the first time in Misiones province in 2012 in a family farm. The aim of this study was to investigate the presence and the genetic diversity of CLA in Argentina between 2012 and 2016. A nested-PCR method using specific primers allowed the detection of CLA in citrus leaves by amplification of a 1160-bp fragment from the 16S rDNA. A total of 76 of 1187 samples (6.4%) were positive for CLA. Positive samples were found in all of the years analyzed, being 2016 the one with the largest share (8.5% 21/248). Seven of these fragments from different years and locations were sequenced and confirmed to belong to CLA. These samples were phylogenetically related with other sequences from the rest of the world. The Argentinean sequences did not form a monophyletic group. However, the comparison of CLA isolates using these genomic sequences has shown little variation among isolates and, thus, further analysis using other genomic regions must be conducted.