The development of endomycorrhizal root systems VIII. Effects of soil phosphorus and fungal colonization on the concentration of soluble carbohydrates in roots

Concentrations of phosphorus in shoot and soluble carbohydrates (fructose, glucose, sucrose and fructans) in root were measured in non-mycorrhizal and vesicular-arbuscular (VA) mycorrhizal (Glomus mosseae) leek plants (Allium porrum) raised at six concentrations of soil phosphate. In conditions when an increased concentration of soil phosphate reduced VA mycorrhizal infection, the concentrations of soluble carbohydrates in the root were at a maximum. Therefore the hypothesis that greater concentrations of soluble carbohydrates in roots favour VA mycorrhizal infection is discounted. There was a specific effect of VA mycorrhizas, in that infected roots contained a larger concentration of sucrose than did uninfected roots, in plants with similar phosphorus concentrations in dry matter of shoots. We conclude, first, that increased phosphorus supply from either phosphate addition to soil or VA mycorrhizal infection increases concentration of soluble carbohydrates in leek roots and, secondly, that the VA mycorrhizal root behaves as a particularly strong physiological sink when there is an excess concentration of sucrose in the host

Persistence of DNA of Gaeumannomyces graminis var. tritici in soil as measured by a DNA-based assay

Herdina, Stephen Neate, Suha Jabaji-Hare and Kathy Ophel-Kelle

Isolation of mycoparasitic-related transcripts by SSH during interaction of the mycoparasite Stachybotrys elegans with its host Rhizoctonia solani

Mycoparasitism by antagonistic fungi involves changes in the biochemistry and physiology of both partners. Analysis of genes that are expressed during mycoparasite\ue2\u20ac\u201c host interaction represents a powerful strategy to obtain insight into the molecular events underlying these changes. The aim of this study is to identify genes whose expression is upregulated when the mycoparasite Stachybotrys elegans is in direct confrontation with its host Rhizoctonia solani. Suppression subtractive hybridization (SSH) was used to create a subtracted cDNA library, and differential screening was applied to identify the over-expressed transcripts. We report the analysis of 2,166 clones, among which 47% were upregulated during mycoparasitism. Two hundred and sixtyone clones were sequenced that corresponded to 94 unique genes. Forty-four of these were identified as novel genes, while the remainder showed similarity to a broad diversity of genes with putative functions related to toxin production, pathogenicity, and metabolism. As a result of mycoparasitism, 15 genes belonged to R. solani among which 9 genes were assigned putative functions. Quantitative RT-PCR was used to examine the upregulation of 12 genes during the course of mycoparasitism. Seven genes showed significant upregulation at least at one-time point during interaction of the mycoparasite with its host. This study describes a first step toward knowledge of S. elegans genome. The results present the useful application of EST analysis on S. elegans and provide preliminary indication of gene expression putatively involved in mycoparasitism.NRC publication: Ye