Gaeumannomyces graminis var. tritici was first isolated from rice in 1981. Sheath rot of rice seedling in box culture for machine transplanting was produced by artificial inoculation of the causal organism. Especially sheath rot was developed from crown to leaf sheath above water level. Perithecia were usually formed in dead leaf sheaths and in PDA culture. They were black, globose, and immersed with obliquely erumpent neck. Asci were unitunicate with an apical ring and contained 8 spores. Ascospores were hyline, slender, $80{sim}140;um$ in length. Each spore showed $3{sim}4;septa.$ Based on morphological and cultura characteristics, the isolate from seeds was identified as Gaeumannomyces graminis (Sacc.) Arx & Olivier tritici J. Walker.