Polymorphic restriction patterns of ribosomal internal transcribed spacers in the biocontrol fungus Puccinia carduorum correlate with weed host origin.

The internal transcribed spacer (ITS) regions of ribosomal DNA were amplified by PCR and used to develop genetic markers for isolates of Puccinia carduorum being evaluated for biological control of Carduus thoermeri (musk thistle). Unique patterns were produced upon restriction of ITS DNA amplified from four separate Puccinia spp. Restriction patterns of ITS DNA of isolates of P. carduorum from Carduus acanthoides and C. thoermeri were distinct from those of P. carduorum from Carduus tenuiflorus and Carduus pycnocephalus. By this technique, isolates of P. carduorum from four different weed hosts can be differentiated from other Puccinia spp. and separated into two host groups.