Scytalidium thermophilum plays an important role in determining selectivity of compost produced for growing Agaricus bisporus. The
objective of this study was to characterise S. thermophilum isolates by random amplified polymorphic DNA (RAPD) analysis and
sequence analysis of internally transcribed spacer (ITS) regions of the rDNA, to assess the genetic variation exhibited by this species
complex and to compare this with existing morphological and thermogravimetric data. RAPD analysis of 34 isolates from various
parts of the world revealed two distinct groups, which could be separated on the basis of the differences in the banding patterns
produced with five random primers. Nucleotide sequence analysis of the ITS region, which was ca 536 bp in length, revealed only
very minor variation among S. thermophilum isolates examined. Several nucleotide base changes within this region demonstrated
variation. Genetic distance values among type 1 and 2 S. thermophilum isolates, as determined by ITS sequence analysis, varied by a
value of 0.005%. Molecular analyses carried out in the present study would suggest that isolates within this species complex exhibit
genetic differences which correlate well with morphological variation and thermogravimetric data previously determined.