USE OF (CAT)5 AS A DNA-FINGERPRINTING PROBE FOR FUNGI

A new DNA fingerprinting probe, (CAT),, was evaluated for its ability to detect variation in higher fungi. The probe, which apparently detects variable number tandem repeat (VNTR) loci, was shown to be highly sensitive to genetic variation. The DNA of each of 30 single-basidiospore progeny of a dikaryon of Helerobasidion annosum exhibited a unique fingerprint after PstI restriction, electrophoresis, and in-gel hybridization with the oliganucleotide. Twelve of 28 scored bands were heterozygous in the parent dikaryon. Six bands segregated in the expected 1:1 ratio, and the remaining six exhibited skewed segregation ratios. Two new bands were observed among the progeny but not the parent dikaryon, suggesting a high mutation rate (>0.3%), consistent with other reported VNTR loci. A few new bands were also observed among single-ascospore progeny of a heterokaryotic isolate of Ophiostoma piliferum, a blue-stain fungus. The probe was useful in delineating genotypes (fingerprinting), in identifying infraspecific variants, and, potentially, in quantifying genetic variation. Each tested field isolate of H. annosum displayed a unique fingerprint, except for certain isolates from adjacent trees. Somatic incompatibility tests supported the conclusion that isolates with identical fingerprints were derived from clonal spread of the pathogen over many years through the root systems of adjacent trees. Several fingerprint bands were specific to either of the two host-specialized (on pine and fir) groups of H. annosum in North America, Likewise, several bands were unique to isolates of either of two host-specialized varieties (var. wageneri and var. ponderosum) of Leptographium wageneri, an asexual pathogen native to western North America on Pinaceae. More polymorphisms were seen with the (CAT)S probe than in 21 isozyme markers used in an earlier study.