Tuber melanosporum, when dominant, affects fungal dynamics in truffle grounds.

Summary • The fruiting bodies of the ectomycorrhizal (ECM) fungus Tuber melanosporum are usually collected in an area devoid of vegetation which is defined as a ‘burnt area’ (brule in French). • Here, the soil fungal populations of inside and outside brule were compared in order to understand whether the scanty plant cover was related to a change in fungal biodiversity. Both denaturing gradient gel electrophoresis (DGGE) and molecular cloning of the internal transcribed spacer (ITS) marker were employed on soil DNA to obtain profiles from nine truffle grounds and fungal sequences from one selected truffle ground sampled in two years. • Denaturant gradient gel electrophoresis profiles from the two areas formed two distinct clusters while molecular cloning allowed 417 fungal sequences to be identified. T. melanosporum was the dominant fungus within the brule. There were nine new haplotypes, which had never been detected in fruiting bodies. The Basidiomycota ECM fungi decreased within the brule, indicating a competitive effect of T. melanosporum on the other ECM fungi. • Among other factors, the dynamics of fungal populations seems to be correlated to brule formation.