Iǹtraspecific variation in two species of Suillus from Scots pine (Pinus sylvestris L.) forests based on somatic incompatibility and isozyme analyses



Isolates of Suillus variegatus (Swartz ex Fr.) O. Kuntze and Suillus bovinus (Fr.) O. Kuntze cultured from basidiocarps collected in different geographically located Scots pine (Pinus sylvestris L.) forests were subjected to an analysis of axenic growth rates, somatic incompatibility and electrophoretic isozyme expression. Intraspecific variation in the radial growth rates and at certain putative enzyme loci was detected in these fungal populations which, after tests for somatic incompatibility, were identified as being composed mainly of different clones. Following a numerical analysis of the isozyme data of seven enzyme systems, considerable interspecific dissimilarity (11% similarity) and intraspecific similarity (> 65% similarity) were detected in these fungi. Isozymes of esterase, peptidase and acid phosphatase were conserved within species but differed between these species enabling their unambiguous identification. Isolates of S. variegatus were found in two main clusters that represented the two forest locations from which they were collected. A single putative locus of glutamate oxaloacetate transaminase was found to display isozyroe polymorphism directly related to the forest location of the isolates. No habitat-related isozyme activities could be detected in the isolates of 5. bovinus which, unlike those of S. variegatus, exhibited isozyme expression that was strongly dependent upon the medium. Isolates of S. variegatus and S. botinus identified as originating from the same vegetative clone by somatic incompatibility testing were found to exhibit 100 and 93-97% similarity in their respective isozyme activities. These studies indicate that isozyme analyses in conjunction with somatic incompatibility testing will provide powerful tools for the genetic analysis of ectomycorrhizal communities.