Quantitative assay of Rhizoctonia solani Kühn AG-1 in soil

Combining the advantages of quantitative estimation methods with selective culture and anastomosis grouping techniques, and improved procedure for detecting the population of Rhizoctonia solani Kühn AG-1 in soil is described. In this procedure, the three different inoculum types—sclerotia, colonized plant debris and free hyphae—of the fungus are monitored. Using soil inoculation and recovery experiments, relationships between the existing population of each inoculum type and their correspondingly detectable amounts were established, and it was demonstrated that the different soil types (clay, loam and sandy loam) and the different strains of R. solani AG-1 tested had no effect on this procedure. Assays of samples from 19 natural soil fields showed that this procedure could be used efficiently for the quantitative estimation of R. solani AG-1 in natural soils.