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Physiology and Biochemistry

Observations on the Fungitoxicity of the Phytoalexin, Kievitone. David A. Smith, Lecturer, Plant Biology Department, The University, Hull, HU6 7RX, United Kingdom; Phytopathology 68:81-87. Accepted for publication 13 June 1977. Copyright 1978 The American Phytopathological Society, 3340 Pilot Knob Road, St. Paul, MN 55121. All rights reserved.. DOI: 10.1094/Phyto-68-81.

Kievitone, kievitone hydrate, and three other kievitone derivatives were bioassayed against Aphanomyces euteiches and Rhizoctonia solani in solid and/or liquid media. These five compounds also were assayed on thin-layer chromatography plates versus Fulvia fulva and Cladosporium herbarum. Results from these various bioassays suggested that the fungitoxicity of the phytoalexin, kievitone, depended upon its free phenolic hydroxyl groups and lipophilic side-chain. Kievitone inhibited the growth of A. euteiches and R. solani in solid and liquid aqueous media that were prepared without any organic solvent amendment. Although kievitone had little effect on the radial mycelial growth of Fusarium solani f. sp. phaseoli on agar, it considerably reduced the increase in mycelial dry weight in liquid culture. Kievitone appeared to be as effective a fungitoxicant when assayed in solely aqueous media as it was when incorporated in similar media in the presence of small amounts of organic solvent. The radial mycelial growth of A. euteiches and R. solani was steadily repressed by kievitone; neither fungus appeared to adapt to the phytoalexin. Fusarium solani f. sp. phaseoli, on the other hand, was insensitive to kievitone in agar over a period of 6 days.

Additional keywords: isoflavonoids, antifungal compounds.