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Phytoalexin Induction in Beans Resistant or Susceptible to Fusarium and Thielaviopsis. R. E. Pierre, Plant Pathologist, University of the West Indies, Mona, Jamaica; formerly Research Associate, Department of Plant Pathology, Cornell University, Ithaca, New York 14850; Phytopathology 61:322-327. Accepted for publication 13 October 1970. DOI: 10.1094/Phyto-61-322.

Beans responded to inoculation with pathogens and nonpathogens by producing substances, two of which were found to inhibit germination and growth of fungi. One of these substances (phaseollin) previously has been identified. The second substance apparently is phenolic. It absorbs maximally at 288 nanometers in ethanol. Greater quantities of both phytoalexins were induced in resistant than in susceptible bean lines. The fungi induced different quantities of each phytoalexin, and the phytoalexins appeared to be induced independently. The fungi were differentially sensitive to each phytoalexin. It is suggested that resistance in bean to Fusarium solani f. sp. phaseoli and Thielaviopsis basicola is operative through the formation of two phytoalexins which inhibit the growth of the infecting organisms in vivo, thus restricting the size of the lesions produced in resistant bean lines.