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Biochemistry and Cell Biology

Differential Production of Thaxtomins by Pathogenic Streptomyces Species In Vitro. Rosemary Loria, Department of Plant Pathology, Cornell University, Ithaca NY 14853-5908; Raghida A. Bukhalid(2), Robert A. Creath(3), Roseann H. Leiner(4), Michael Olivier(5), and John C. Steffens(6). (2)(3)(4)(5)Department of Plant Pathology, Cornell University, Ithaca NY 14853-5908; (6)Department of Plant Breeding, Cornell University, Ithaca NY 14853-5908. Phytopathology 85:537-541. Accepted for publication 1 February 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/Phyto-85-537.

Streptomyces scabies and S. acidiscabies, causal agents of potato scab, produced the phytotoxin thaxtomin A and, to a lesser extent, other thaxtomins in oatmeal broth (OMB). Two nonpathogenic strains, Streptomyces lividans TK 24 and Streptomyces sp. 84-05, did not produce thaxtomins in OMB. Though thaxtomin A was produced by S. scabies strain 87-22 in potato broth, fresh potato starch, and some commercial starch preparations, production was much greater in OMB than in other media tested. Thaxtomin A was not produced in Luria broth or tryptic soy broth. Production of thaxtomin A by 87-22 was suppressed by 0.5% glucose in OMB but was stimulated by up to 5.0% glucose in oatmeal agar. Streptomyces scabies strain 87-22 produced 4.25 µg thaxtomin A per milliliter of OMB while strain 84-34 produced 0.17 µg per milliliter of OMB. Streptomyces acidiscabies strains 84-110 and 90-25 produced similar amounts of thaxtomin A, 2.65 and 4.45 µg per milliliter of OMB, respectively. Strain 87-22 was much more virulent on tubers of Chippewa, a scab-susceptible potato cultivar, than was strain 84-34. A tuber slice bioassay was useful for detection of thaxtomins in culture media and for identifying pathogenic Streptomyces strains.