VIEW ARTICLE

Physiology and Biochemistry

Metabolites from Pseudomonas corrugata Elicit Phytoalexin Biosynthesis in White Clover. David L. Gustine, United States Department of Agriculture, Agricultural Research Service, U.S. Regional Pasture Laboratory, University Park, PA 16802; Robert T. Sherwood(2), Barton G. Moyer(3), and Felix L. Lukezic(4). (2)(3)United States Department of Agriculture, Agricultural Research Service, U.S. Regional Pasture Laboratory, University Park, PA 16802; (4)Department of Plant Pathology, The Pennsylvania State University, University Park 16802. Phytopathology 80:1427-1432. Accepted for publication 6 July 1990. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/Phyto-80-1427.

Metabolites and viable cells of Pseudomonas corrugata from liquid culture medium elicited biosynthesis of the phytoalexin medicarpin in ladino white clover (Trifolium repens) leaflets and callus. The biologically active elicitor components were soluble in 80% ethanol. They were partially purified by removing components greater than 3,500 Da by dialysis and fractionating by preparative reversed-phase high-performance liquid chromatography (HPLC). None of the four fractions separated by HPLC elicited appreciable quantities of medicarpin in callus, but fraction 1 combined with fraction 4 elicited high concentrations of medicarpin. Any combination of fractions 2, 3, and 4 synergistically elicited medicarpin in callus. Elicitor activity was concentration-dependent. The active fractions were acidic in solution, but their elicitor activity was not dependent on low pH. Fraction 1 contained primarily uncharacterized reducing carbohydrate and phosphate. Fractions 2 and 3 were composed primarily of two related, unidentified fluorescent compounds, and fraction 4 contained another unidentified fluorescent compound.