Distribution and molecular characterization of the root endophyte Phialocephala fortinii along an environmental gradient in the boreal forest of Alberta

Phialocephala fortinii is a common root endophytic fungus with a wide geogr aphic distribution and little, if any, host specificity. Little is known ab out its habitat specificity, although there is evidence to suggest that hig h water tables may restrict the occurrence of P. fortinii in wetlands. We t ested this hypothesis by determining the distribution of P. fortinii along a sand dune - wetland complex. Isolates of P. fortinii, identified on the b asis of cultural and morphological characteristics, were obtained from the roots of vascular plants across the moisture gradient. Three 'cultural grou ps' were recognized among these isolates. Thirty-three of these isolates we re compared smr,nt themselves and to strains of known identity using PCR/RF LP analysis of the ITS region and a portion of the 28S subunit of rDNA The restriction digest profiles of all isolates were identical to those of P. f ortinii for 4 restriction enzymes. DNA sequences, from a subset of these st rains, showed a low percent sequence divergence confirming the reliability of the RFLP data. The same analyses were done with two strains of Leptodont idium orchidicola, a culturally similar root endophyte, to ensure that this taxon was not among the transect isolates. DNA data showed a clear differe nce between P. fortinii and L. orchidicola but did not discriminate among c ultural groups. Thus, P. fortinii showed no habitat specificity and occurre d in both xeric and hydric sites. RFLP profiles and ITS sequences showed li ttle variation among isolates of P. fortinii and among the isolates of L. o rchidicola.