An evaluation of the fungal 'morphotype' concept based on ribosomal DNA sequences

Abstract

In studies of fungal endophyte communities, mycelia sterilia are commonly isolated from plant substrates and grouped into morphotypes on the basis of cultural characteristics. In Polygonum multiflorum one hundred and sixty-nine strains of mycelia sterilia were isolated and grouped into 27 morphotypes. Six randomly selected morphotypes, each with 2-3 representatives, were subsequently subjected to ribosomal DNA sequence analysis. Nucleotide sequence similarities of the rDNA internal transcribed spacer (ITS) regions and the 5.8S gene were compared using UPGMA cluster analysis. Comparison of nucleotide sequences revealed high levels of similarity (ca. 91.63-99.53%) among strains within morphotypes. ITS and 5.8S sequences of species within various genera from GenBank were obtained to estimate levels of nucleotide similarity within and between well-established genera and species. This study verifies on the basis of ribosomal DNA sequence analysis the validity of these 'morphotypes' as taxonomic groups. A dendogram, illustrating relatedness of the morphotypes and reference taxa from GenBank is also presented.