Molecular characterization of Pseudocercosporella herpotrichoides isolates by amplification of ribosomal DNA internal transcribed spacers

In order to determine whether a given isolate of Pseudocercosporella herpotrichoides. the cause of eyespot disease of cereals, belongs to the W‐type or the R‐type, we have developed a test based on the polymerase chain reaction (PCR). Sequences of the internal transcribed spacer (ITS) region of the ribosomal genes were determined for three different isolates of each pathotype. Primers complementary to variable sequences were specifically chosen to amplify differentially DNA from W‐ and R‐types. Specific reaction conditions of the PCR assay were experimentally determined by testing four isolates of each type that exhibit a wide range of sensitivity to fungicides.