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Germination and Growth of Five Fungi in Low-Oxygen and High-Carbon Dioxide Atmospheres. John M. Wells, Plant Pathologist, ARS, USDA, 2021 South Peach Avenue, Fresno, California 93727; M. Uota, Horticulturist, ARS, USDA, 2021 South Peach Avenue, Fresno, California 93727. Phytopathology 60:50-53. Accepted for publication 23 July 1969. DOI: 10.1094/Phyto-60-50.

Mycelial growth of Alternaria tenuis, Fusarium roseum, Botrytis cinerea, Cladosporium herbarum, and Rhizopus stolonifer on a liquid glucose-salt medium at 19 C in atmospheres of 21, 4, 2, 1, , , and 0% oxygen decreased linearly with decreasing O2 concentrations below 4%. Mean per cents growth of the respective organisms at 4% oxygen, as compared to growth in air, were 31, 38, 45, 50, and 85%; at 0% oxygen, only Rhizopus grew significantly. Growth of A. tenuis, B. cinerea, R. stolonifer, and C. herbarum in atmospheres of 10, 20, 30, and 45% CO2 plus 21% O2 decreased linearly with increasing CO2 concentrations, and was inhibited about 50% in an atmosphere of 20% CO2. Growth of F. roseum, however, was stimulated at 10% CO2, and inhibited 50% at 45% CO2. When the O2 concentration was 2% and thereby limiting to growth, CO2 at the lower levels tested stimulated growth of all the fungi except R. stolonifer. Low oxygen atmospheres inhibited germination of all fungi tested. Responses to high CO2 atmospheres, however, varied. At 16% CO2, the germination of R. stolonifer, B. cinerea, and C. herbarum was inhibited 90%. A. tenuis was inhibited only at CO2 levels higher than 32%, and F. roseum was stimulated by concentrations of CO2 as high as 16%. When the oxygen concentration was 1% and thereby limiting, CO2 at the lower levels tested stimulated the germination of all fungi except A. tenuis.