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Reassessment of the Role of Saprophytic Activity in the Ecology of Thielaviopsis basicola

December 1997 , Volume 87 , Number  12
Pages  1,214 - 1,219

M. E. Hood and H. D. Shew

Department of Plant Pathology, North Carolina State University, Raleigh 27695

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Accepted for publication 21 August 1997.

The ability of Thielaviopsis basicola to survive saprophytically in soil was investigated using root tissue from susceptible hosts as organic substrates. Inoculum densities were lower in soils amended with root tissue than in nonamended controls after 2 and 4 weeks of incubation. The greatest decrease occurred in soils containing the highest concentration of root tissue or in soils in which root tissue included the soluble components of the living root. Reproduction by T. basicola also was examined in axenic media containing either killed root pieces or various carbohydrates as the sole carbohydrate source. T. basicola utilized killed root tissue as a carbohydrate source in axenic media, particularly in cultures in which root tissue included the soluble components. Enzymatic activities of T. basicola, however, did not result in maceration of the root tissue. T. basicola utilized sucrose and cellobiose, but did not utilize structural carbohydrates such as cellulose, hemicellulose, or pectin. Based on the absence of significant saprophytic ability, T. basicola should be classified ecologically as an obligate parasite.

© 1997 The American Phytopathological Society