Identification of green algal endophytes as the alternate phase of Acrosiphonia (Codiolales, Chlorophyta) using ITS1 and ITS2 ribosomal DNA sequence data

The internal transcribed spacer regions of the nuclear ribosomal DNA cistro n of green algal endophytes, previously identified as Chlorochytrium inclus um Kjellman and Codiolum petrocelidis Kuckuck, were sequenced. Culture stud ies have implicated marine Chlorochytrium and Codiolum-like cells in the Li fe histories of a number of macrophytic green algae. The identity of the en dophytes was resolved by comparing DNA sequences from unicells endophytic i n the foliose red alga Mazzaella splendens (Setchell et Gardner) Hommersand and in the crustose phase of Mastocarpus papillatus (J. Agardh) Kylin, wit h sequences from species of Acrosiphonia, Urospora, Ulothrix, and Monostrom a. All endophyte isolates were more closely related to species of Acrosipho nia than to those of Urospora, Ulothrix or Monostroma. The results support previous culture studies, and conclusively identify the endophytes obtained in the field as alternate life history phases of one or more Acrosiphonia species in southern British Columbia, Canada.