Detection and molecular characterization of ‘<i>Candidatus</i> Liberibacter’ in Colombian oil palms affected by Lethal Wilt Disease

Lethal wilt (LW), also known as "Marchitez Letal (ML)" in Colombia, is an endemic disease affecting oil palms (<i>Elaeis guineensis</i> Jacq.) and is a leading cause of crop loss. The disease is characterized by the drying of leaflets from the tip to the base, primarily impacting the lower third of the plant and progressively moving upward. This progression leads to physiological disturbances, including necrosis at the tips of immature inflorescence bracts (spines) and the detachment of bunch fruits, ultimately causing wilting. As a phytosanitary measure, infected palms are eradicated to prevent further spread of the disease. The primary goal of this research was to identify the bacteria associated with LW and to validate a molecular detection method. A 16S amplicon-based analysis was employed to identify and compare the microbial diversity in LW-affected palm tissues with those of healthy plants. Among the 16 OTUs corresponding to different bacterial genera found in all LW samples, taxonomic classification and symptomatology suggested that the bacteria closely associated with LW belong to the genus <i>Candidatus</i> Liberibacter. Further phylogenetic analysis indicated that these bacteria are part of the Rhizobiaceae family, grouping closely with other species of the genus <i>Candidatus</i>. Liberibacter. The concentration of the pathogen in different oil palm tissues was determined using droplet digital PCR (ddPCR) and quantitative PCR (qPCR), expressed in copies/µL in the LW samples. This study represents the first report of '<i>Candidatus</i> Liberibacter sp'. being associated with lethal wilt in oil palms of the Arecaceae family in Colombia. The findings from this research have the potential to contribute significantly to the development of effective management strategies to prevent crop losses.