VIEW ARTICLE

Ecology and Epidemiology

Effect of Pseudomonas putida and a Synthetic Iron Chelator on Induction of Soil Suppressiveness to Fusarium Wilt Pathogens. Fran M. Scher, Former research associate, Department of Botany and Plant Pathology, Colorado State University, Fort Collins 80523, Current address of senior author: Advanced Genetic Sciences, Inc., P. O. Box 1373, Manhattan, KS 66502; Ralph Baker, professor, Department of Botany and Plant Pathology, Colorado State University, Fort Collins 80523. Phytopathology 72:1567-1573. Accepted for publication 9 June 1982. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-1567.

When Pseudomonas putida isolated from a Fusarium-suppressive soil, ethylenediaminedi-O-hydroxyphenylacetic acid (EDDHA), or its ferrated form (FeEDDHA), was added to conducive soil, the soil became suppressive to Fusarium wilt pathogens of flax, cucumber, and radish. Experimental evidence suggested that competition for iron (Fe) was responsible for the suppressiveness in these systems since Fe appeared to be necessary for germ-tube elongation of Fusarium oxysporum f. sp. lini microconidia. FeEDDHA and siderophores produced by P. putida were considered to have higher Fe stability constants than siderophores shown to be produced by various pathogenic fusaria. Suppressiveness was not induced by DTPA or FeEDTA, which have lower Fe stability constants than FeEDDHA. Suppressiveness from adding both P. putida and FeEDDHA to conducive soil was additive, but not interactive, in short-term experiments. P. putida did not produce fluorescent siderophores on agar medium containing 10^–4M Fe unless EDDHA or DTPA (2 mg/ml) was added. This indicated that these ligands created an iron deficiency in the medium. Presence of EDTA in the agar medium inhibited production of fluorescent siderophores. It is suggested that the management of Fe availability in the infection court, through Fe competition, can induce suppressiveness to Fusarium wilt pathogens.