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Endophytic Bacteria in Symptom-Free Cotton Plants. I. J. Misaghi, Department of Plant Pathology, University of Arizona, Tucson 85721; C. R. Donndelinger, Department of Plant Pathology, University of Arizona, Tucson 85721. Phytopathology 80:808-811. Accepted for publication 14 February 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-808.

Isolates of Erwinia sp., Bacillus sp., B. pumilus, B. brevis, Clavibacter sp., and Xanthomonas sp. were recovered from surface-sterilized radicles, roots, stems, unopened flowers, and bolls of greenhouse- and field-grown cotton plants of cultivars Delta Pine 41 (DP41) and Delta Pine 61 (DP61). These bacteria could not be eliminated from seeds and the above-ground organs by stringent surface sterilization methods. Erwinia sp. was the most prevalent bacterium with an average isolation frequency of 69% for DP41 and 51% for DP61. An antibiotic-resistant mutant of Erwinia sp. was recovered from stems, flowers, bolls, and roots of DP41 at average reisolation frequencies of 97, 82, 77, and 48%, respectively, after its introduction into germinated seeds. Reisolation frequencies of an antibiotic-resistant Bacillus sp. from the above tissues were 34, 12, 5, and 0%, respectively. In contrast, antibiotic-resistant mutants of B. pumilus, B. brevis, Clavibacter sp., and Xanthomonas sp. could not be reisolated from these same organs. Similar results were obtained with DP61. The recovered endophytes were not pathogenic to the two cultivars.