Antibacterial Activity of Tea and Coffee Wastes Against Some Plant Pathogenic Pseudomonas syringae Strains

Abstract

In vitro and greenhouse trials were conducted to elucidate the potential use of extracts of tea and coffee wastes to control plant diseases caused by the bacterial pathogens, Pseudomonas syringae pv. pisi (race 1 and 2) and P. s. pv. phaseolicola (race 1). The antibacterial activity was measured as the diameter of the inhibition zone in agar and also by periodical viable cell counts in laboratory tests. The effect on the hypersensitive reaction and the potential for disease control after leaf infiltration and seed treatment were studied on bean plants in the greenhouse. Results showed that both the tea and coffee extracts possessed antibacterial activity against the three pathogens, but that the effects varied depending on the strain and the test method. Strong reduction of halo blight disease and improvement in plant growth was obtained in presence of the coffee extract. For the halo blight pathogen, P. s. pv. phaseolicola, there was a good correlation between the results from the viable cell count method and the greenhouse tests, but the results from the in vitro studies did not agree with those from greenhouse as regards the P. s. pv. pisi strains. It is suggested that the component(s) in tea and coffee responsible for controlling the bean pathogen may not be the same as that for the pea pathogens.