Previous View
APSnet Home
Phytopathology Home


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 g thaxtomin A per milliliter of OMB while strain 84-34 produced 0.17 g per milliliter of OMB. Streptomyces acidiscabies strains 84-110 and 90-25 produced similar amounts of thaxtomin A, 2.65 and 4.45 g 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.

Additional keywords: acid scab, common scab, streptomycetes, toxin.