Xanthomonas perforans Colonization Influences Salmonella enterica in the Tomato Phyllosphere

Abstract

ABSTRACTSalmonella entericararely grows on healthy, undamaged plants, but its persistence is influenced by bacterial plant pathogens. The interactions betweenS. enterica,Xanthomonas perforans(a tomato bacterial spot pathogen), and tomato were characterized. We observed that virulentX. perforans, which establishes disease by suppressing pathogen-associated molecular pattern (PAMP)-triggered immunity that leads to effector-triggered susceptibility, created a conducive environment for persistence ofS. entericain the tomato phyllosphere, while activation of effector-triggered immunity by avirulentX. perforansresulted in a dramatic reduction inS. entericapopulations.S. entericapopulations persisted at ∼10 times higher levels in leaves coinoculated with virulentX. perforansthan in those whereS. entericawas applied alone. In contrast,S. entericapopulations were ∼5 times smaller in leaves coinoculated with avirulentX. perforansthan in leaves inoculated withS. entericaalone. Coinoculation with virulentX. perforansincreasedS. entericaaggregate formation; however,S. entericawas not found in mixed aggregates withX. perforans. Increased aggregate formation byS. entericamay serve as the mechanism of persistence on leaves cocolonized by virulentX. perforans.S. entericaassociation with stomata was altered byX. perforans; however, it did not result in appreciable populations ofS. entericain the apoplast even in the presence of large virulentX. perforanspopulations. Gene-for-gene resistance againstX. perforanssuccessively restrictedS. entericapopulations. Given the effect of this interaction, breeding for disease-resistant cultivars may be an effective strategy to limit both plant disease andS. entericapopulations and, consequently, human illness.