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Physiology and Biochemistry

Association of the Phytoalexin Kievitone with Single-Gene Resistance of Cowpeas to Phytophthora vignae. J. E. Partridge, Graduate Research Associate, Department of Plant Pathology, University of California, Riverside 92502, Present address of the senior author: Department of Plant Pathology, University of Nebraska, Lincoln 68503; N. T. Keen, Associate Professor, Department of Plant Pathology, University of California, Riverside 92502. Phytopathology 66:426-429. Accepted for publication 2 October 1975. DOI: 10.1094/Phyto-66-426.

Cowpeas monogenically resistant to Phytophthora vignae accumulated the isoflavonone phytoalexin kievitone after inoculation, but near-isogenic susceptible cowpea plants produced it at much lower rates. Kievitone was present in the resistant plants at 10-fold or higher concentrations than were required to inhibit mycelial growth of P. vignae in culture by 50%. Inoculated plants also produced the isoflavonoids daidzein and coumestrol, but no differences were seen in their rates of accumulation between inoculated resistant and susceptible plants. The data support the hypothesis that the basis for the expression of monogenic resistance of cowpea plants to P. vignae is a specific derepression of kievitone biosynthesis.