RELATEDNESS OF THE ERICOID ENDOPHYTES SCYTALIDIUM-VACCINII AND HYMENOSCYPHUS-ERICAE INFERRED FROM ANALYSIS OF RIBOSOMAL DNA

Phenotypic similarities between the root endophytes Scytalidium vaccin ii, a hyphomycete, and Hymenoscyphus ericae, an ascomycete, led to spe culation that S. vaccinii might be the anamorph of H. ericae. To test this hypothesis, we used the polymerase chain reaction to amplify port ions of the ribosomal DNA from the ex-type cultures of each species an d from cultures of several endophytes putatively identified as Scytali dium 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. va ccinii and most isolates tentatively identified as H. ericae from Nort h America. However, restriction mapping of the amplified fragment reve aled that the apparent differences were an artifact resulting from the presence of one or two insertions in the small and large subunit ribo somal RNA genes of the North American isolates. Sequencing of homologo us regions of the small subunit and the 5' internal transcribed spacer indicated that sequence divergence between pairs of isolates identifi ed as Scytalidium and H. ericae was low, ranging from 1.2-3.5%, as com pared to divergence of up to 24% with H. monotropae, another ericoid e ndophyte. Although there was variation among the isolates, molecular a nd morphological evidence suggests that S. vaccinii and H. ericae are anamorph and teleomorph states of a single taxon.