Occurrence of Pseudomonas fluorescens and P. putida associated to tomato pith necrosis in Brazil

ABSTRACT In 2016, several reports emerged of fresh-market staked tomato plants with severe symptoms of pith necrosis and premature death in commercial cultivation areas in the states of Paraná and Minas Gerais, Brazil, which are similar to those caused by Pseudomonas corrugata. Four bacterial strains were isolated from infected tissue samples and characterized as Gram-negative, aerobic, and fluorescent on King’s B Medium. LOPAT tests were performed and the isolate UFU H120 was classified into group Vb (+ + − + −) and the isolates UFU H3, UFU H6, and UFU H21 into group Va (− + − + −). The pathogenicity of the isolates was confirmed by artificial inoculation on tomato plants of Santa Cruz type, cv. Kada Gigante, and Koch’s postulates were accomplished successfully. The isolates sequences of their 16S rRNA gene region were compared with those deposited in GenBank, the isolate UFU H120 aligning with Pseudomonas fluorescens (99,45% similarity) and the isolates UFU H3, UFU H6, and UFU H21 with Pseudomonas putida (99.2, 99.53 and 99.64% similarity, respectively). Notably, P. fluorescens and P. putida are most known as saprophytic bacteria normally present in the soil, although both of these species have already been reported to infect tomato plants in Italy. However, so far, there have not been any reports of such bacteria being phytopathogenic on tomato or any crop in Brazil. Thus, to our knowledge, this is the first report of pith necrosis of such occurrence in Brazil. RESUMO Em 2016 em tomateiro tutorado para consumo in natura, foram observadas plantas com sintomas graves de necrose da medula e morte prematura da planta, em áreas de cultivo comercial nos estados do Paraná e Minas Gerais, Brazil, similares aos causados por Pseudomonas corrugata. Quatro cepas bacterianas foram isoladas a partir de amostras de tecido infectado e caracterizadas como Gram negativas, crescimento aeróbico e fluorescimento em meio de cultura King B. Testes LOPAT foram realizados e o isolado UFUH120 foi classificado no grupo Vb (+ + - + -) e isolados UFU H3, UFU H6 e UFU H21 no grupo Va (- + - + -). A patogenicidade dos isolados foi confirmada pela inoculação artificial em tomate Santa Cruz cv. Kada Gigante e os postulados de Koch realizados com sucesso. O sequenciamento da região do gene 16S rRNA dos isolados foi realizado e as sequências obtidas comparadas com as depositadas no GenBank, o isolado UFU H120 foi alinhado com Pseudomonas fluorescens (99.45% de similaridade) e os isolados