Pith Necrosis of Tomato Caused by Pseudomonas viridiflava May Not Decrease Production

Aims: This study aimed to measure the losses in the production of tomato plants caused by the bacteria P. viridiflava.

Study Design: Experiments were performed in a completely randomized design with six replicates.

Place and Duration of Study: The study was conducted on the Caçador experimental station of the Agricultural Research and Rural Extension Enterprise of Santa Catarina (EPAGRI) from October to April during 2017/2018 and 2018/2019 crop season.

Methodology: Bacteria were isolated from tomato plants with pith necrosis symptoms, using nutrient agar. The isolated strain was identified by a scheme of tests for bacteria that emit fluorescence, known as LOPAT, and by sequencing the 16S rDNA region. Tomato plants were cultivated for two seasons during 2017/2018 and 2018/2019. In the first year the cultivar Paronset was cultivated and in the next season the experiment was performed with the cultivars Compack, Nagai, Paronset and Pizzadoro. During the production season, tomato fruits were harvested and the weight was accounted for. At the beginning of the first bunch formation, the stems of the plant were inoculated with wood sticks containing bacterial colonies removed from a 48h-Petri dish culture medium. Tomato plants cultivated as control treatments were not inoculated. At the end of the cultivation seasons, the stems were cut to analyze the pith necrosis progress.

Results: In both cultivation seasons, there was no decrease in the production associated with the pith necrosis caused by P. viridiflava EPAGRI BacPvT1 because the total weight of fruits harvested from inoculated plants was not statistically different compared to the non-inoculated plants. The disease progressed in all inoculated plants and adventitious root formation as external symptoms was observed.

Conclusion: The bacteria Pseudomonas viridiflava EPAGRI BacPvT1, one of the etiological agents of pith necrosis of tomato, may not decrease the production. Even causing some injuries, it may be not cause any damage.