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Suppression of Major and Minor Pathogens by Fluorescent Pseudomonads in Solarized and Nonsolarized Soils. A. Gamliel and J. Katan. Department of Plant Pathology and Microbiology, The Hebrew University of Jerusalem, Faculty of Agriculture, Rehovot 76100, Israel. Phytopathology 83:68-75. Accepted for publication 4 September 1992. Copyright 1993 The American Phytopathological Society. doi:10.1094/Phyto-83-68.

Strains of fluorescent pseudomonads increased the growth of tomato plants in nonsolarized soil but not in solarized soil. Vital staining showed that fluorescent pseudomonads colonize the root cortex and, apparently, internally colonize the younger lateral roots of artificially inoculated plants growing in nonsolarized soil. The minor pathogen Penicillium pinophilum caused growth retardation of tomato and cotton plants. It colonized tomato roots in nonsolarized, methyl bromide-fumigated, and solarized soils (to a much lesser extent). Inoculation of tomato roots with fluorescent pseudomonads or transplanting tomato roots to solarized soil suppressed colonization by Penicillium pinophilum and nullified plant-growth retardation. Inoculation of plant roots with plant growth-promoting strains of Pseudomonas putida. P. fluorescens, and P. alcaligens reduced the incidence of disease caused by Sclerotium rolfsii in bean, Fusarium wilt in cotton and tomato, and reduced colonization of cotton roots by pathogens that cause these diseases. Induced suppressiveness against S. rolfsii in bean and Fusarium oxysporum f. sp. vasinfectum in cotton was observed in solarized soil. We suggest that fluorescent pseudomonads are effective agents in suppressing both major and minor pathogens in soil.

Additional keywords: beneficial microorganisms, deleterious microorganisms, melon, plant growth-promoting rhizobacteria.