Antibacterial activity of plant diffusate against Xanthomonas campestris pv Citri

Two hundred and eight diffusates from various plants such as forest trees, herbs, shrubs, fruit trees, spices, vegetables, food legumes, fodder, oil seed, fibre crops, cereals and ornamentals were evaluated through agar diffusion assay to determine their inhibitory action, if any, against Xanthomonas campestris pv. citri. Diffusates from the majority of forest trees, herbs and shrubs showed an inhibitory effect against strain XC-100 of the bacterium. Diffusates from various parts of Phyllanthus emblica, Acacia nilotica, Sapindus mukorossi and Terminalia chebula, which exhibited an inhibition zone measuring 4.83-6.00 mm at 50 g l(-1) concentration, appeared to be the most effective. These diffusates showed an inhibitory effect even at a concentration of 1.25 g l(-1). These diffusates at concentrations of 50, 20 and 10 g l(-1) were significantly (P < 0.01) more effective in reducing the number of lesions on detached leaves and fruits, thus exhibiting protective as well as curative actions. Diffusates from higher plants, therefore, appear to be potential antimicrobial agents which could be used for the management of citrus canker disease.