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Ecology and Epidemiology

Factors Affecting Zoospore Production by Phytophthora megasperma var. sojae. Linda L. Eye, Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824; B. Sneh(2), and J. L. Lockwood(3). (2)(3)Department of Botany and Plant Pathology, Michigan State University, East Lansing, MI 48824; (2)Present address: Institute for Nature Conservation Research, University of Tel-Aviv, Ramat-Aviv, Israel. Phytopathology 68:1766-1768. Accepted for publication 19 June 1978. Copyright © 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-1766.

Cultures of Phytophthora megasperma var. sojae grown on lima bean agar in petri dishes were flooded with distilled water to induce formation of zoospores. Maximum numbers of 10⁴-10⁵ zoospores/ml (15 ml of suspension per plate) were produced when 6-day-old cultures of isolates of races 1 to 6 received five changes of distilled water each at 30-min intervals, followed by incubation in darkness at 20 C for at least 8 hr.