VIEW ARTICLE

Effects of Oxygen and Carbon Dioxide Tensions on Growth of Several Species of Phytophthora. D. J. Mitchell, Former Research Assistant, Department of Plant Pathology, University of California, Riverside 92502, Present address of senior author: Department of Plant Pathology, University of Wisconsin, Madison 53706; G. A. Zentmyer, Professor, Department of Plant Pathology, University of California, Riverside 92502. Phytopathology 61:787-791. Accepted for publication 5 February 1971. DOI: 10.1094/Phyto-61-787.

Growth of Phytophthora capsici, P. citrophthora, and P. palmivora was more rapid on sucrose-asparagine agar at 5% O₂ than at the normal atmospheric O₂ concentration; maximum radial growth of P. parasitica occurred in air. Growth of all species on the solid medium was reduced at O₂ levels below 5%. With the exception of P. palmivora, the growth of the other Phytophthora species in a sucrose-asparagine liquid medium decreased with decreasing O₂ concentrations below that of air. Growth on the solid medium was stimulated by the addition of 5% CO₂ when the O₂ level was 1%, but growth of most isolates in liquid or solid media was reduced by CO₂ concentrations above 5% in comparison to growth at the same O₂ level without added CO₂. At 15% CO₂ plus 20% O₂, growth in liquid or solid media was reduced to two-thirds of the control.