Influence of peroxidase and catalases on mycelial growth and pycnidium production by Plenodomus meliloti in light and darkness

Mycelial colonies of Plenodomus meliloti Mark.-Let., incitant of brown root rot of legumes, were of similar size whether cultured in the light or in darkness on an agar medium. However, numerous pycnidia were produced only in the light. In the presence of 'active' horseradish peroxidase, beef liver catalase, and polyphenol oxidase enzymes, mycelial growth in comparison to controls was accelerated. Numerous pycnidia were produced in cultures incubated in light or darkness. When horseradish peroxidase and beef liver catalase were denatured by autoclaving, cultures were similar to controls. Aspergillus niger catalase inhibited mycelial growth and pycnidium production. Association of environmental conditions, peroxidase and catalase enzymes, and pathogenicity is discussed.