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Identification and Effects on Xanthomonas campestris pv. malvacearum of Two Phytoalexins from Leaves and Cotyledons of Resistant Cotton. Margaret Essenberg, Department of Biochemistry, Oklahoma State University, Stillwater 74078; Mary d'Arcy Doherty(2), Betty K. Hamilton(3), Veronica T. Henning(4), Ellen C. Cover(5), Steve J. McFaul(6), and William M. Johnson(7). (2)(3)(4)(5)(6) Department of Biochemistry, Oklahoma State University, Stillwater 74078; (7)Langston University Research Program, Langston University, Langston, OK 73050, and Department of Plant Pathology, Oklahoma State University, Stillwater 74078. Phytopathology 72:1349-1356. Accepted for publication 22 December 1981. Copyright 1982 The American Phytopathological Society. DOI: 10.1094/Phyto-72-1349.

Two compounds that inhibit growth of Xanthomonas campestris pv. malvacearum were isolated from leaves and cotyledons of inoculated bacterial blight-resistant lines of cotton (Gossypium hirsutum). Chromatographic and spectral properties indicated that they are 2, 7-dihydroxycadalene and its oxidation product, the yellow fluorescent compound lacinilene C. Extracts of inoculated blight-susceptible or uninoculated blight-resistant leaves contained much lower amounts of both compounds. 2,7-Dihydroxycadalene at 0.35 mM caused a 50% reduction in the number of bacterial generations in a liquid culture bioassay. Preparations of lacinilene C from plants of resistant cotton lines WbM(0.0) and Im 216 were optically active, but exhibited ellipticities of opposite signs; they caused 50% inhibition at approximately 0.4 mM and 1.5 mM, respectively. The amounts of 2,7-dihydroxycadalene and lacinilene C extracted from inoculated resistant leaves were approximately one-tenth of the amounts required to account for the observed inhibition of X. campestris pv. malvacearum, if those compounds were uniformly distributed throughout the tissue water.

Additional keywords: bacterial blight of cotton, hypersensitive response, 2,7-dihydroxycadalene, lacinilene C.