VIEW ARTICLE

Physiology and Biochemistry

Zinniol Production by Alternaria Species. P. J. Cotty, Department of Plant Pathology, University of Arizona, Tucson 85721; I. J. Misaghi, Department of Plant Pathology, University of Arizona, Tucson 85721. Phytopathology 74:785-788. Accepted for publication 6 March 1984. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-785.

Thirty-one isolates of 10 pathogenic Alternaria spp. were tested for in vitro production of zinniol, a nonselective phytotoxin, on a casamino acids-enriched medium. Analyses were performed by gas-liquid and thin-layer chromatography with synthetic zinniol as a standard. Of the seven pathogenic large-spored, long-beaked Alternaria spp. tested, A. carthami, A. macrospora, A. porri, A. solani, A. tagetica, and an unnamed isolate from pods of Phaseolus vulgaris produced zinniol but A. brassicae and a nonpathogenic isolate of A. zinniae did not. Zinniol was not detected in filtrates of three pathogenic species lacking large spores and long beaks (A. alternata, A. citri, and A. raphani). The quantity of zinniol produced varied greatly among species, among different isolates of a single species, and between trials of the same isolate. All hosts of the Alternaria spp. tested were sensitive to zinniol at 50- 200 μg/ml. The evolutionary conservation of zinniol production in pathogenic large-spored Alternaria spp. may be indicative of its importance in pathogenesis.