Relatedness of the Ericoid Endophytes Scytalidium Vaccinii and Hymenoscyphus Ericae Inferred from Analysis of Ribosomal DNA

ABSTRACT

Phenotypic similarities between the root endophytes Scytalidium vaccinii, a hyphomycete, and Hymenoscyphus ericae, an ascomycete, led to speculation that S. vaccinii might be the anamorph of H. ericae. To test this hypothesis, we used the polymerase chain reaction to amplify portions of the ribosomal DNA from the ex-type cultures of each species and from cultures of several endophytes putatively identified as Scytalidium or H. ericae based on colonial and morphological similarities. An initial restriction fragment analysis of the amplified rDNA separated the H. ericae isolates from England from the ex-type culture of S. vaccinii and most isolates tentatively identified as H. ericae from North America. However, restriction mapping of the amplified fragment revealed that the apparent differences were an artifact resulting from the presence of one or two insertions in the small and large subunit ribosomal RNA genes of the North American isolates. Sequencing of homologous regions of the small subunit and the 5′ internal transcribed spacer indicated that sequence divergence between pairs of isolates identified as Scytalidium and H. ericae was low, ranging from 1.2-3.5%, as compared to divergence of up to 24% with H. monotropae, another ericoid endophyte. Although there was variation among the isolates, molecular and morphological evidence suggests that S. vaccinii and H. ericae are anamorph and teleomorph states of a single taxon.

Key Words:

• ericoid mycorrhizae
• molecular systematic
• nuclear ribosomal RNA genes
• polymerase chain reaction