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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, ½, ¼, 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.