Use of Polymerase Chain Reaction To Detect the Take-All Fungus, Gaeumannomyces graminis, in Infected Wheat Plants.

Gaeumannomyces graminis, the causative agent of take-all disease of wheat, barley, and oats, was detected in infected wheat seedlings by using the polymerase chain reaction to amplify Gaeumannomyces-specific DNA fragments. Nested primers and two rounds of amplification were used to amplify two fragments, approximately 287 and 188 bp in size, from G. graminis-infected wheat seedlings. The use of nested primers greatly decreased the number of nonspecific amplification products. Polymerase chain reaction products were not obtained with DNA from seedlings infected with several other phytopathogenic fungi or with DNA from uninfected seedlings. Amplified products were visualized on agarose gels, and their identities were confirmed by DNA hybridization. This method did not require culturing the fungus and has potential for detecting G. graminis in infested wheat, barley, or oat fields.