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Fungi Associated with Roots of Apple Seedlings Grown in Soil from an Apple Replant Site. B. A. Jaffee, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. G. S. Abawi, New York State Agricultural Experiment Station, Cornell University, Geneva 14456, and W. F. Mai, Department of Plant Pathology, Cornell University, Ithaca. Plant Dis. 66:942-944. Accepted for publication 16 February 1982. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-942.

Apple seedlings (Northern Spy) exhibited severe stunting and root discoloration when grown in steamed field soil amended with 5% (v/v) untreated field soil obtained from an orchard with a history of apple replant disease. Isolation of pathogenic fungi from discolored root segments harvested at different time intervals was variable. However, isolation made from roots of seedlings grown in steamed field soil amended with washed feeder roots obtained from seedlings previously grown in 5% untreated field soil consistently yielded Cylindrocarpon lucidum and Pythium irregulare. C. lucidum and P. irregulare were generally isolated from black and orange lesions, respectively. Both fungi were pathogenic to Northern Spy apple seedlings grown under growth chamber conditions.