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Symptomless Carriers of the Tomato Fusarium Wilt Pathogen. J. Katan, Department of Plant Pathology and Microbiology, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel; Phytopathology 61:1213-1217. Accepted for publication 17 May 1971. DOI: 10.1094/Phyto-61-1213.

Various weeds grown in soils naturally infested with Fusarium oxysporum f. lycopersici did not show wilt, although their tissues harbored Fusarium. Roots of weeds belonging to the genera Oryzopsis, Digitaria, Amaranthus, and Malva were colonized with F. oxysporum f. lycopersici, which constituted a part of the natural population existing in these soils. When planted under controlled conditions in soils naturally infested with races 1 or 2 of the pathogen, these plants were also colonized with the respective races. Roots of the four weeds were colonized to various degrees when artificially inoculated with any tested isolate of the pathogen originating either from the roots of the weeds or diseased tomato plants. Roots of other wild or cultivated plants were also colonized with the pathogen to various degrees when artificially inoculated, eggplants being distinguished by an extensive colonization and partial stunting. Quantitative estimation of the pathogen in the tissues, by maceration and subsequent dilution, showed that the population in inoculated weed tissues was 1-4% of the quantity in diseased tomato tissues. A method is suggested for determining the natural occurrence of symptomless carriers of a soil pathogen.

Additional keywords: quantitative estimation of Fusarium in plant tissues, survival.