VIEW ARTICLE

Disease Control and Pest Management

Lack of a Role for Fluorescent Siderophore Production in the Biological Control of Pythium Damping-Off of Cucumber by a Strain of Pseudomonas putida. T. C. Paulitz, U.S. Department of Agriculture, Agricultural Research Service, Horticultural Crops Research Lab, 3420 NW Orchard Ave, Corvallis, OR 97330, Present address: Department of Plant Science, Macdonald College, 21,111 Lakeshore Road, Ste. Anne de Bellevue, Quebec, H9X 1C0, Canada; J. E. Loper, U.S. Department of Agriculture, Agricultural Research Service, Horticultural Crops Research Lab, 3420 NW Orchard Ave, Corvallis, OR 97330. Phytopathology 81:930-935. Accepted for publication 11 March 1991. 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, 1991. DOI: 10.1094/Phyto-81-930.

Hyphal growth but not sporangial germination of Pythium ultimum was inhibited by the synthetic iron chelating compound ethylenediamine (di-o-hydroxyphenylacetic acid) (EDDHA) on water agar and by strain N1R of Pseudomonas putida on King’s medium B. Eight prototrophic derivatives of N1R (deficient in fluorescent siderophore [pyoverdine] biosynthesis [Pvd^–]) were obtained by Tn5 mutagenesis. Pvd^– derivatives did not inhibit hyphal growth of P. ultimum on King’s medium B, but protected cucumber seedlings from Pythium damping-off in three different agricultural soils at levels statistically indistinguishable from the parental strain, N1R. Therefore, pyoverdine production by strain N1R was not critical to biocontrol of Pythium damping-off of cucumber under the conditions of this study.