Plant-growth regulator, imidazole-4-carboxamide, produced by the fairy ring forming fungus Lepista sordida.

Rings or arcs of fungus-regulated plant growth occur often on the floor of woodlands, in agricultural areas, and in grasslands worldwide. These rings are commonly called "fairy rings". A plant-growth regulating compound was isolated from a fairy ring forming fungus, Lepista sordida , and its chemical structure was identified as imidazole-4-carboxamide (ICA) by spectroscopic analyses including single-crystal X-ray diffraction techniques. ICA inhibited the growth of turfgrass and rice seedling. On the other hand, in a greenhouse experiment, this compound increased rice grain yield by 26% compared with control.