, Volume 43, Issue 2, pp 211-216

Pyrrolnitrin and phenazine production by Pseudomonas cepacia , strain 5.5B, a biocontrol agent of Rhizoctonia solani

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Abstract

Rhizoctonia stem rot of poinsettia caused by Rhizoctonia solani is controlled by strain 5.5B of Pseudomonas cepacia when poinsettia cuttings are rooted in polyfoam rooting cubes. Experiments were conducted to isolate and characterize secondary metabolites from strain 5.5B that were inhibitory towards R. solani. Inhibitory compounds were detected in fractions processed from liquid cultures of strain 5.5B. The most inhibitory compound isolated was pyrrolnitrin. A purple pigment consistently produced in culture by strain 5.5B was isolated and identified as 4,9-dihydroxyphenazine-1,6-dicarboxylic acid dimethyl ester, a phenazine. In vitro inhibition of R. solani occurred with the phenazine.