The genome of 13 Suillus isolates, mostly originating from Mediterranean and Alpine regions was screened by using a range of PCR-based techniques. Amplification of the ITS region led to fragments of the same length irrespective of the species, whereas RFLP revealed interspecific variability. Random oligonucleotides for RAPD amplification and primers for microsatellites led to polymorphic fingerprints revealing intraspecific differences. In addition, microsatellite fingerprinting allowed separation of strains with different symbiotic capabilities (for example: Suillus collinitus strains 24 and 31), as well as strains originating from the same zone.The results suggest that a range of molecular probes used on the same isolates can provide both specific fingerprints for selected fungal strains and tools to investigate the physiological characteristics of ectomycorrhizal fungi.

Production of enzymes which degrade plant cell wall macromoleculea has been studied in relatively few ericoid fungal isolates, although these polymers arc a major component of the organic litter and an important source of nutrients for these fungi. Our aims were to investigate whether the ability to degrade the wall pectic component, only reported for one isolate, is a general feature of ericoid fungi. Of about 35 isolates from different geographic regions, all were capable of growing on pectin as the sole carbon source. Polygalacturonase (PG) activity was detected to a different degree in the culture filtrates and independently of the fungal growth rate. Solid and liquid isoelectric focusing allowed separation and identification of several polygalacturonase isoforms. Among the fungal isolates investigated, those from the northern hemisphere produced mostly acidic isoforms, whereas isolates from South Africa secreted more abundantly basic isoforms. However, purification and biochemical characterization of several PG isoforms from the different isolates revealed an optimal activity in the acidic pH range for all the PG enzymes tested. Polygalacturonase enzymes seem to be an important component of the enzymatic arsenal secreted by ericoid fungi during their saprotrophic life. In addition, they could also play a role during root colonization, since penetration across the plant cell wall is a prerequisite for the establishment of endomycorrhizal symbiosis.