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Physiology and Biochemistry

Increased Chlamydospore Production by Phytophthora cinnamomi Using Sterols and Near-Ultraviolet Light. L. Englander, Assistant professor, Department of Plant Pathology-Entomology, University of Rhode Island, Kingston 02881; W. Turbitt, graduate research assistant, Department of Plant Pathology-Entomology, University of Rhode Island, Kingston 02881. Phytopathology 69:813-817. Accepted for publication 16 February 1979. Copyright 1979 The American Phytopathological Society. DOI: 10.1094/Phyto-69-813.

A regimen was developed using near-ultraviolet light, temperatures between 23 and 28 C, and a natural medium (V8 agar) supplemented with β-sitosterol for consistently producing high yields of chlamydospores of Phytophthora cinnamomi. Addition of β-sitosterol to V8 agar at 1040 μg/ml stimulated chlamydospore production in cultures incubated in the light but not in those incubated in the dark. In the dark, growth (dry weight) was stimulated by sterol at 20 and 40 μg/ml; in the light, however, no stimulation was detected with sterol up to 200 μg/ml. Chlamydospores produced on V8 agar plus sterol were more abundant in cultures illuminated with 100, 200, or 400 μW cm2 light in the 310420 nm (near-UV) region than in the 470610 or 550725 nm region at the same intensities or in the dark. Chlamydospore production comparable to that in 310420 nm light was obtained with Blacklight Blue fluorescent lamps, which emit predominantly near-UV light. Optimum intensity of Blacklight Blue light for sporulation was 100200 μW cm2.

Additional keywords: soil fungi.