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The Effect of Visible and Near-Visible Radiation on Sporangium Production by Phytophthora cinnamomi. G. A. Zentmyer, Professor, Department of Plant Pathology, University of California, Riverside, CA 92502; O. K. Ribeiro, Postgraduate Research Associate, Department of Plant Pathology, University of California, Riverside, CA 92502. Phytopathology 67:91-95. Accepted for publication 11 June 1976. Copyright 1977 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-67-91.

The effect of light quality and intensity on the production of Phytophthora cinnamomi sporangia was studied using cultures that were grown in a chemically-defined liquid medium. Cultures were irradiated at intensities ranging from 3 μW cm2 to 200 μW cm2, and at wavelengths between 312 and 1,350 nm. Sporangia were produced at all wavelengths and intensities tested, and in darkness. Sporangium production was stimulated in the near-UV by intensities up to 100 μW cm2. At 200 μW cm2 there was no significant difference in sporangium production in wavelengths ranging from the near-UV to infrared (312 nm-1,350 nm). These results indicate that sporangium production by P. cinnamomi is light-variable, but not light-dependent.

Additional keywords: soil extract, pea broth, sporangium morphology, light.