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Effect of Soil Microflora on the Interaction of Three Plant-Parasitic Nematodes with Celery. J. L. Starr, Department of Plant Pathology, Cornell University, Ithaca, New York 14853, Present address senior author: Department of Plant Pathology, North Carolina State University, Raleigh 27607; W. F. Mai, Department of Plant Pathology, Cornell University, Ithaca, New York 14853. Phytopathology 66:1224-1228. Accepted for publication 2 March 1976. Copyright © 1976 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-66-1224.

In growth chamber tests, celery roots grown in organic soil collected from celery fields (field soil) and inoculated with 10,000 Meloidogyne hapla eggs developed extensive root galling and root necrosis. The amount of root necrosis observed after a 4-week incubation period depended upon the initial concentration of M. hapla: 500 eggs per seedling caused no increase in root necrosis over that observed on noninoculated roots, but 5,000 or more eggs per seedling increased it significantly. Root necrosis was not observed on nematode-infected roots in autoclaved soil. Pythium polymorphon, which was isolated from necrotic galls and roots, was the primary cause of necrosis of M. hapla-infected roots from nonautoclaved field soil. In autoclaved field soil, M. hapla-infected roots inoculated with P. polymorphon developed more necrosis than did roots not infected by the nematode at similar fungal inoculum levels. Celery growth was reduced more in the same nonautoclaved field soil than in autoclaved field soil infested with Pratylenchus penetrans. The low level of root necrosis in nonautoclaved field soil was not increased by inoculation with the nematode. More nematodes were recovered from roots in nonautoclaved field soil infested with P. penetrans than from roots in autoclaved field soil. Celery growth was not reduced in either soil when seedlings were inoculated with Paratylenchus projectus.

Additional keywords: plant pathogenic nematodes, secondary invaders.