The research results show that the opportunity for rapid diversification of Agaricomycetes fungi is the encounter with Flowering plant in the late Cretaceous period 90 million to 70 million years ago. The evolution of mycorrhizal symbiosis between Agaricomycetes fungi and Flowering plant roots has occurred several times in each taxon independently since about 250 million years ago. Among them, the mycorrhizal symbiotic evolution that occurred independently in the late Cretaceous in five taxa, Cortinarius, Inocybe, and Boletaceae, was accompanied by rapid Species diversity.