Management of bacterial canker of tomato caused by Clavibecter michiganensis subsp. michiganensis (Smith and Davis et al.) using different antibiotics

In an attempt to control bacterial canker of tomato, a very hard-to-control disease, both in-vitro and in-vivo studies were conducted using antibiotics alone or in combinations with other antibiotics and with copper oxychloride. Using paper disc diffusion assay and 50 ppm - 400 ppm concentrations, tetracycline+streptomycin produced the largest inhibition zone (22.8 mm) followed by tetracycline  alone (22.0) at highest concentration after 48 hrs incubation. The result of antibiotic combination streptomycin and gentamicin were statistically at par with those of tetracycline+streptomycin combination. However, streptomycin alone proved to be ineffective. Antibiotic concentrations of 250 ppm and higher were sufficient to inhibit the in-vitro bacterial growth. In case of screen-house studies, combination of tetracycline and copper oxychloride gave minimum % disease severity (5.40%), as compared to inoculated but untreated control in which case the % disease severity was 56.6 %. The same combination (i.e. tetracycline+copper oxychloride) also proved to be more effective than other treatments in term of enhancing yield per plant (1147.7g), plant height (102.0 cm), plant dry weight (130.8g) and other parameters. The better performance of this combination treatment could be attributed to its interactive effect. This study suggested that combination of antibiotics should be used for proper disease management and further combinations of different antibiotics in different concentrations should be evaluated. Keywords: Antibiotics; Bacteria; Clavibecter; Tomato http://dx.doi.org/10.19045/bspab.2019.80128