VIEW ARTICLE

Physiology and Biochemistry

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.