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An Antibacterial Compound from Solanum phureja and its Role in Resistance to Bacterial Wilt. J. C. Zalewski, Research Assistant, Department of Plant Pathology, University of Wisconsin, Madison 53706, Present address of senior author: Department of Botany and Plant Pathology, Oregon State University, Corvallis 97331; Luis Sequeira, Professor, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 65:1336-1341. Accepted for publication 10 June 1975. DOI: 10.1094/Phyto-65-1336.

We reported previously that ethanolic extracts from tissues of wilt-resistant clones of Solanum phureja inhibited growth of Pseudomonas solanacearum to a greater degree than extracts from wilt-susceptible Solanum tuberosum cultivars. We now report on some of the chemical properties of one of the components of the main inhibitory fraction and on attempts to determine, by genetic means, the possible involvement of this fraction in the mechanism of disease resistance. After partial purification by paper and column chromatography, the inhibitory fraction (IP) exhibited a strong ultraviolet absorption maximum at 264 nm, which shifted to 282 nm, accompanied by loss of biological activity, after treatment with 2 N HCl. Elution patterns from Sephadex G-10 columns showed nearly coincident peaks for bacterial growth inhibition and content of the 264-282 nm absorbing compound(s). However, a quantitative assay for this particular component did not yield a positive correlation between its presence and resistance of various potato clones to P. solanacearum. Clones derived from segregating hybrid progeny from a cross between resistant (R) and susceptible (S) clones of S. phureja were used to test the relationship between IP content and resistance. Disease reaction segregated independently from total inhibitory content, and from content of the 282 nm-absorbing compound as well. From our original data, based on a limited number of clones, a correlation between resistance and content of bacterial growth inhibitors appeared possible. The more critical evidence from segregating progenies of a R × S cross failed to support such a hypothesis.