Whole Genome Sequencing Reveals New Bacterial Pathogen Affecting Lettuce Plants

Abstract Bacterial leaf spot in lettuce was reported as a quarantine pathogen in 2012 in Trinidad. The pathogen associated with the disease was isolated from lettuce in some of the major growing areas. The isolated bacteria revealed two distinct morphologies, constantly associated with bacterial leaf spot symptoms. The pathogenicity study revealed that both bacterial organisms were able to cause the disease. PCR amplification and sequencing of the bacterial pathogens exhibiting yellow mucoid and creamy white colonies using 16S rRNA primers were revealed as Xanthomonas (BLS1, BLS5, BLS6, BLS7, BLS8, BLS9) and Acidovorax (BLS4), respectively. To distinguish Xanthomonasfrom Acidovorax, species-specific primers was used to determine Xanthomas campestris pv. vitians. This study has confirmed that strains BLS1, BLS5, BLS6, BLS7, BLS8, BLS9 were Xanthomas hortorum pv. vitians (Xanthomas campestris pv. vitians). Nevertheless, to probe deeply at the genome level about Acidovorax BLS4 being the first time noticed infecting lettuce and being difference from the Xanthomonas, the whole genome sequencing was performed. This has revealed for the first time Paracidovorax avenae (Acidovorax avenae) as a leaf spot pathogen of lettuce. The sequence from the whole genome has been annotated to reveal several genes involved in transport, resistance, stress, motility, virulence, all of which are important factors that contribute to pathogenesis. Some of these genes include the type IV pilus twitching motility protein PilT, YihY/virulence factor BrkB family protein, Svx/AvrXca family virulence/avirulence protein virulence RhuM family protein, and organic hydroperoxide resistance protein.