Comparison Between a DNA-Based Assay and a Soil Bioassay in Quantifying the Amount of Gaeumannomyces Graminis Var. Tritici in Soil
A slot-blot hybridization assay for quantifying the amount of Gaeumannomyces graminis var. tritici (Ggt) in diseased roots and in soil has been developed, using a specific and sensitive DNA probe (pG158). The procedure involves separation of organic matter from soil, DNA extraction of soil organic matter, and a slot-blot hybridization assay. Soil of different types was collected to a depth of 10 cm and organic matter between 0.35–1.4 mm in size was separated from this soil. Using a slot-blot hybridization assay, it was found that Ggt was mostly present in the organic matter fraction greater than 0.5 mm and in soil at a depth of 5 cm.
The slot-blot hybridization assay correlated well with a soil bioassay, as measured by the percentage of seminal roots with Ggt lesions, in estimating the amount of Ggt inoculum in soil. Artificially inoculated soils and naturally infested soils were used for the comparison between the two assays. This rapid and reliable DNA-based assay is being used in conjunction with a model of take-all disease development to predict disease levels in the field due to Ggt.
KeywordsRhizoctonia Solani Diseased Root Seminal Root Infested Soil Crown Root
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