Quantification of the ectomycorrhizal fungus Piloderma croceum in soil microcosms. The relative amount of P. croceum mycelium was measured by real-time quantitative PCR (qPCR) in the presence or absence of Streptomyces sp. AcH 505, the soil microbial filtrate, and pedunculate oak microcuttings. In the presence of microcuttings quantification was performed with bulk soil as well as rhizosphere samples. The bars indicate qPCR abundances of P. croceum in the absence (a,d) and presence (rhizosphere (b,e) and bulk soil (c,f) of the host plant. Quantification was performed with the ITSP1f/r (a,b,c) and Pilo127f/r (d,e,f) primer pairs. The qPCR abundances are reported in terms of delta Ct values, which indicate the number of cycles at which the fluorescent signal exceeds the background level and surpasses the threshold established in the exponential region of the amplification plot. Error bars denote standard errors; bars with different letters are significantly different according to one-way ANOVA and the Tukey HSD test (P < 0.05). Note that the presence of the host plant modulates the responses of the microorganisms to one-another.