Role of Penicillic Acid in the Phytotoxicity of Penicillium cyclopium and Penicillium canescens to the Germination of Corn Seeds

Penicillium cyclopium and Penicillium canescens cultures inhibited the germination of corn. The phytotoxic compound was isolated by solvent extraction and thin-layer chromatography on silica gel. The phytotoxin was identified as penicillic acid by mass spectrometry, nuclear magnetic resonance, and infrared spectroscopy. Gas-liquid chromatography on a capillary glass column separated the two epimeric forms of penicillic acid. The maximum production of penicillic acid was obtained with P. cyclopium cultures grown at 25°C. The phytotoxicity of penicillic acid was manifested by its ability to alter the germination of corn. The percent inhibition of germination was directly proportional to the logarithm of the penicillic acid concentration. Growth of the main root was reduced 50% by concentrations of 500 μg/ml.