VIEW ARTICLE

Ecology and Epidemiology

Effects of Pseudomonas fluorescens on Potato Plant Growth and Control of Verticillium dahliae. S. D. Leben, Department of Plant Pathology, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser 99350; J. A. Wadi(2), and G. D. Easton(3). (2)Department of Botany, The Islamic University of Gaza, Gaza Strip, Gaza, Israel; (3)Department of Plant Pathology, Washington State University, Irrigated Agriculture Research and Extension Center, Prosser 99350. Phytopathology 77:1592-1595. Accepted for publication 7 July 1987. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-1592.

Pseudomonas fluorescens strain M-4, an antagonist of Verticillium dahliae in vitro, was studied to determine its potential as an inhibitor of V. dahliae and growth promoter of potato plants. In pot experiments of soil fortified with V. dahliae, fresh weights of shoots and roots and plant height from potato seed pieces dusted with P. fluorescens were significantly greater for plants treated with P. fluorescens. In addition, the number of propagules of V. dahliae in stem tissue was significantly lower for treated potatoes. In pasteurized soil, potato growth was not enhanced by P. fluorescens, even though the roots were colonized by the bacteria significantly more than in soil infested with V. dahliae. In 1982 and 1984 field trials, P. fluorescens applied to hand-planted seed pieces as a dust or liquid coating containing 10⁸ cfu/ml resulted in root population densities of about 10⁴ cfu/g of root, similar to populations on roots in greenhouse pot experiments. In the field, however, P. fluorescens had no effect on yield, percent U.S. No. 1 tubers, or incidence of Verticillium wilt.