Pseudomonas aeruginosa produces secondary metabolites that have biological activity against plant pathogenic Xanthomonas species

• The metabolites activity of Pseudomonas aeruginosa against three Xanthomonas species.
• In general higher disease control was achieved with preventive treatments.
• Electron microscopy studies showed that metabolites changed cell morphology.
• The number of lesions caused by three Xanthomonas species was reduced around 94%.
• Common bacterial blight of bean had about 73% of reduction in lesion percentage.

The bioactivity of compounds produced by Pseudomonas aeruginosa (LN strain), against three Xanthomonas species was investigated under greenhouse conditions and using electron microscopy. Chromatographic fractions EAP, VLC3, VLC4, VLC3d and VLC4f were tested against Xanthomonas axonopodis pv. malvacearum, X. axonopodis pv. phaseoli and X. axonopodis pv. citri by disc diffusion. Fractions with antibiotic activity were tested in vivo under greenhouse conditions and their bioactivity was evaluated. Scanning electron microscopy showed that VLC4f affects biofilm formation while VLC4f and VLC3d both affect cell morphology. The semi-purified fractions controlled bacterial diseases caused by Xanthomonas spp. when sprayed on plants under greenhouse conditions. The VLC4f fraction showed superior results in disease management, reducing the number of lesions on cotton and orange leaves by 94%, and reducing disease severity in bean leaves by 73%. The data suggest that the fractions were effective and have potential as an alternative to conventional bactericides in the control of plant diseases caused by Xanthomonas sp under greenhouse conditions.

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