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Etiology and Epidemiology

Early Development of Pythium polymorphon on Celery Roots Infected by Meloidogyne hapla. James L. Starr, Former Research Assistant, Department of Plant Pathology, Cornell University, Ithaca, NY 14853, Senior authorís present address: Department of Plant Pathology, North Carolina State University, Raleigh 27607; James R. Aist, Assistant Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Phytopathology 67:497-501. Accepted for publication 23 September 1976. Copyright © 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-497.

Meloidogyne hapla-infected and M. hapla-free celery roots were inoculated with Pythium polymorphon; samples taken at 24-hr intervals were observed by interference-contrast light optics. Root-knot galls were colonized by 24 hr after inoculation, but invasion of M. hapla-free roots was not noted until 48 hr. A greater percentage of galled than of nongalled root segments was colonized at 72 hr. After ingress, P. polymorphon colonized both galled and nongalled root segments at apparently similar rates. The fungus seemed to invade nongalled portions of galled roots from infected galls. Aqueous extracts of galled and nongalled roots, either autoclaved or filter-sterilized and added to 1% glucose, were equally supportive of P. polymorphon growth in vitro. The results do not support the concept that galled roots provide nutrients for growth of P. polymorphon that are deficient in nongalled roots, but do suggest that factors attractive to the fungus may originate in the galls.

Additional keywords: disease complexes, histopathology.