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Compounds Exuded by Phaseolus vulgaris That Induce a Modification of Rhizobium etli Lipopolysaccharide

September 1997 , Volume 10 , Number  7
Pages  903 - 910

Dominik M. Duelli and K. Dale Noel

Department of Biology, Marquette University, Milwaukee, WI 53233, U.S.A.

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Accepted 7 July 1997.

Exudates released from germinating seeds and roots of a black-seeded bean (Phaseolus vulgaris cv. Midnight Black Turtle Soup) induce an antigenic change in the lipopolysaccharide (LPS) of Rhizobium etli CE3. By spectroscopic analyses and chromatographic comparisons with derived standards, the chemical structures of the aglycone portions of the major inducing molecules from seed exudate were deduced, and they were identified as delphinidin, cyanidin, petunidin, and malvidin. These anthocyanidins were present in seed exudate mainly as glycosides, the chief inducer being delphinidin 3-glucoside. Also present were 3-glucosides of petunidin and malvidin and glycosides of cyanidin and delphinidin. Seed exudate from a bean variety deficient in anthocyanins did not induce the LPS conversion. The ability of root exudate to induce an antigenic change in the LPS was due to compounds other than anthocyanins.

Additional keywords: flavonoid, rhizosphere, symbiosis.

© 1997 The American Phytopathological Society