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Auxin-Induced Resistance to Common Scab Disease of Potato Linked to Inhibition of Thaxtomin A Toxicity


Tegg, RS and Gill, WM and Thompson, HK and Davies, NW and Ross, JJ and Wilson, CR, Auxin-Induced Resistance to Common Scab Disease of Potato Linked to Inhibition of Thaxtomin A Toxicity, Plant Disease, 92, (9) pp. 1321-1328. ISSN 0191-2917 (2008) [Refereed Article]

DOI: doi:10.1094/PDIS-92-9-1321


Production of the phytotoxin thaxtomin A by pathogenic Streptomyces spp. is essential for induction of common scab disease in potato. Prior studies have shown that foliar application of sublethal concentrations of 2,4-dichlorophenoxyacetic acid (2,4-D) and other auxin or auxin-like compounds significantly reduced severity and occurrence of common scab in subsequently produced tubers. However, the means of disease suppression by these compounds was not known. We confirm the disease suppressive activity of 2,4-D. Detailed tuber physiological examination showed that lenticel numbers, lenticel external dimensions, and periderm thickness and structure, physiological features believed to be critical to Streptomyces scabiei infection, were not substantially changed by 2,4-D treatments, negating a possible mechanism for disease suppression through alteration of these structures. In contrast, our studies show accumulation of 2,4-D in tubers of treated plants occurs and is associated with an enhanced tolerance to thaxtomin A. Applying 2,4-D to cultures of S. scabiei did not significantly alter in vitro growth of the pathogen. Thaxtomin A production by the pathogen was inhibited by 2,4-D, but only at the highest rate tested (1.0 mM), which is at least 200-fold more than is found in 2,4-D treated tubers. These data suggest 2,4-D has no direct effect on the pathogen or its virulence. Confirmatory evidence from studies with Arabidopsis thaliana seedlings demonstrated that the auxins 2,4-D and IAA ameliorate thaxtomin A toxicity. The evidence presented whereby auxin treatment inhibits toxicity of thaxtomin A secreted by the pathogen suggests a novel indirect means of disease suppression. © 2008 The American Phytopathological Society.

Item Details

Item Type:Refereed Article
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Horticultural production
Research Field:Horticultural crop protection (incl. pests, diseases and weeds)
Objective Division:Plant Production and Plant Primary Products
Objective Group:Horticultural crops
Objective Field:Field grown vegetable crops
UTAS Author:Tegg, RS (Dr Robert Tegg)
UTAS Author:Gill, WM (Dr Warwick Gill)
UTAS Author:Thompson, HK (Dr Hannah Thompson)
UTAS Author:Davies, NW (Associate Professor Noel Davies)
UTAS Author:Ross, JJ (Associate Professor John Ross)
UTAS Author:Wilson, CR (Professor Calum Wilson)
ID Code:48802
Year Published:2008
Web of Science® Times Cited:30
Deposited By:Agricultural Science
Deposited On:2008-08-01
Last Modified:2009-04-01

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