A volatile factor inducing transmissible lysis in Gaeumannomyces graminis (Sacc.) Arx and Olivier var. tritici Walker

Filtered water extract of Gabalong soil with a recent history of take-all in wheat caused lytic plaques to form in agar cultures of a virulent strain of Gaeumannomyces graminis var. tritici. The plaques resembled those produced by Bdellovibrio on plate seeded with bacteria. However, there was no evidence of the presence of bacteria, viruses, or mycoplasmas. The lytic factor was transmissible in culture filtrates to fresh subcultures of the fungus. Exposure of young healthy colonies to sublethal doses of ultraviolet light also induced transmissible lysis. The lytic factor was heat-stable, passed through a 25-nm filter, and was not affected by nuclease (enzymes) or severe irradiation with UV light. It also induced bysis in several other strains of G. graminis. Lysis was always preceded by a growth-stimulatory effect on the fungus. The lytic factor was active as a volatile chemical which induced transmissible lysis and continued to be formed, apparently as a self-perpetuating agent, in lysing cultures of the fungus.