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Inhibition of Bacterial Growth by Extracts from Potato Tissues. J. C. Zalewski, Research Assistant, Department of Plant Pathology, University of Wisconsin, Madison 53706; Luis Sequeira, Professor, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 63:942-944. DOI: 10.1094/Phyto-63-942.

Ethanolic extracts of tuber, stem, and leaf tissues of Solanum phureja and S. tuberosum ‘Russet Burbank’ inhibited growth of the wilt-inducing bacterium, Pseudomonas solanacearum. Inhibitory activity was consistently higher (two- to three-fold) in extracts from wilt-resistant clones of S. phureja than in those from the wilt-susceptible S. tuberosum. Inhibitory activity was reduced in extracts of S. phureja plants grown at low light intensity 6,046 lx (600 ft-c), a condition known to reduce resistance to the bacterium. In liquid culture, low concentrations of the inhibitor increased the lag period and decreased the logarithmic phase growth rate of P. solanacearum. Concentrations that were bactericidal to P. solanacearum did not inhibit growth of Erwinia atroseptica or E. carotovora. Partial purification yielded an active fraction with ultraviolet absorption maximum at 264 nm and chemical properties differing from those of previously described antimicrobial compounds from potato tubers.

Additional keywords: Pseudomonas solanacearum, antibiotics, disease resistance.