Isolates of Pisolithus and Scleroderma species
from different northern temperate and tropical geographical regions were
subjected to
analyses of pure culture morphology, colony growth rates, isozyme (allozyme)
variation and ribosomal DNA (rDNA) restriction
fragment length polymorphisms (RFLPs). Cultural characteristics enabled
clear species separation of isolates and together with growth
rates suggested geographically-linked intraspecific variability in the
Pisolithus populations. Combined or method-specific hierarchical
cluster analyses of allozyme polymorphisms and RFLPs of the fungal internal
transcribed spacer (ITS) and intergenic spacer (IGS)
sequences confirmed the Scleroderma species groupings and considerable
geographical and host-linked variation in the Pisolithus
population. Isolates of Pisolithus from the Philippines were genetically
very homogeneous and distinct from less related isolates from
Europe, Scandinavia and North America. Based on the ITS–RFLP and
isozyme polymorphism data, the isolates investigated probably
represent four different ‘species groupings’ which supports
similar findings from recent taxonomic and genetic studies of Australian
Pisolithus species.