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Role of Antibiotics Produced by Chaetomium globosum in Biocontrol of Pythium ultimum, a Causal Agent of Damping-Off. A. Di Pietro, Institute of Botany, University of Basel, 4056 Basel, Switzerland, Present address: Department of Horticultural Sciences, Cornell University, New York State Agricultural Experiment Station, Geneva, NY 14456; M. Gut-Rella(2), J. P. Pachlatko(3), and F. J. Schwinn(4). (2)(3)Ciba-Geigy AG, 4002 Basel, Switzerland; (4)Institute of Botany, University of Basel, 4056 Basel, Switzerland. Phytopathology 82:131-135. Accepted for publication 23 July 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/Phyto-82-131.

Production of antifungal compounds by Chaetomium globosum and the role in suppression of Pythium damping-off of sugarbeet were evaluated. Two metabolites with antifungal activity against Pythium ultimum, 2-(buta-1,3-dienyl)-3-hydroxy-4-(penta-1,3-dienyl)-tetrahydrofuran (BHT) and the epidithiadiketopiperazine, chaetomin, were isolated from liquid cultures of C. globosum. BHT was produced in 1% malt extract medium by six of eight tested C. globosum strains, whereas chaetomin was produced in 1% corn steep medium by five of nine tested strains. The ability of the nine C. globosum strains to produce chaetomin in liquid culture was correlated with the efficacy to suppress Pythium damping-off of sugarbeet in heat-pasteurized soil. Moreover, chaetomin was extracted from pasteurized soil inoculated with C. globosum strain Cg-13, an effective biocontrol strain, but not from pasteurized soil inoculated with ADP-13, a spontaneous variant of Cg-13 unable to suppress Pythium damping-off. Chaetomin was a hundred times as inhibitory to mycelial growth of P. ultimum as BHT in a bioassay in microtiter plates. Activity of chaetomin was comparable to the fungicide metalaxyl and five to 10 times higher than that of the epidithiadiketopiperazine, gliotoxin. Results suggest that chaetomin production in soil plays an important role in antagonism of C. globosum against P. ultimum.

Additional keywords: antibiosis, mode of action, soilborne diseases.