The object of the invention is to provide a method for developing a novel species by means of interspecific crossbreeding among P. eryngii (DC.:Fr.) Quel., P. eryngii (DC.:Fr.) Quel. var. elaeoselini, P. eryngii (DC.:Fr.) Quel. var. tuoliensis C. J. Mou and P. nebrodensis (DC.:Fr.) Quel., which are not native in Japan, and P. ostreatus (Jacq.: Fr.) Kummer, which is native in Japan and the novel species obtained by the method and is also to provide a novel species of Pleurotus spp. carrying both a P. eryngii (DC.:Fr.) Quel. gene and a P. ostreatus (Jacq.: Fr.) Kummer gene by crossbreeding P. ostreatus (Jacq.: Fr.) Kummer with P. eryngii (DC.:Fr.) Quel. var. tuoliensis C. J. Mou, P. nebrodensis (DC.:Fr.) Quel. or P. eryngii (DC.:Fr.) Quel. var. ferulae Lanzi, thereby obtaining a strain capable of further crossbreeding with P. eryngii (DC.:Fr.) Quel., P. eryngii (DC.:Fr.) Quel. var. elaeoselini or the like.
