VIEW ARTICLE

Disease Control and Pest Management

Suppression of Pythium ultimum-Induced Damping-Off of Cotton Seedlings by Pseudomonas fluorescens and its Antibiotic, Pyoluteorin. C. R. Howell, Research plant pathologist, Science and Education Administration, U.S. Department of Agriculture, National Cotton Pathology Research Laboratory, P.O. Drawer JF, College Station, TX 77840; R. D. Stipanovic, research chemist, Science and Education Administration, U.S. Department of Agriculture, National Cotton Pathology Research Laboratory, P.O. Drawer JF, College Station, TX 77840. Phytopathology 70:712-715. Accepted for publication 16 January 1980. 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, 1980. DOI: 10.1094/Phyto-70-712.

Strain Pf-5 of Pseudomonas fluorescens was antagonistic in vitro to Pythium ultimum. An antibiotic, pyoluteorin (4,5-dichloro-1 H-pyrrol-2-yl-2,6-dihydroxyphenyl ketone), was isolated from cultures of the Pf-5 strain and found to be inhibitory to P. ultimum, but not to R. solani. Treatment of cottonseed with pyoluteorin or with P. fluorescens at the time of planting in P. ultimum-infested soil increased seedling survival from 33 to 65% and from 28 to 71%, respectively. Although effective as a seed treatment, pyoluteorin was adsorbed and inactivated by the soil colloids when added directly to soil.