Phylogenetic analyses, based upon nuclear small-subunit ribosomal RNA gene sequences, of four ‘chlorosarcinoid’ species referred to Planophila Gerneck show that the genus is polyphyletic. The type species, P. laetevirens Gerneck, is closely related to species in the Ulotrichales, Ulvophyceae. The monotypic sarcinoid genus Pseudendocloniopsis is the closest relative of Planophila; the two genera represent the addition of a new morphological type to the Ulotrichales. Planophila microcystis (Dangeard) Kornmann & Sahling forms a clade at the base of the Ulvophyceae with Oltmannsiellopsis, and thus belongs to the Oltmannsiellopsidales. This result is also supported by the Oltmannsiellopsis-like ultrastructure of P. microcystis zoospores. Planophila sp. B from Antarctica, which has Trebouxia-like pyrenoid structure, is a trebouxiophyte closely related to Chlorella-like unicellular coccoids, Stichococcus bacillaris and Prasiola species. This is the first robustly supported molecular phylogenetic analysis that places Prasiola in the Trebouxiophyceae. As shown previously, P. terrestris Groover & Hofstetter belongs to the Chaetopeltidales, Chlorophyceae. Dangemannia gen. nov. (type species: D. microcystis (Dangeard) comb. nov.), Floydiella gen. nov. (type species: F. terrestris (Groover & Hofstetter) comb. nov.) and Pabia gen. nov. (type: P. signiensis sp. nov.) are proposed.

The total DNA of ten isolates of different chlorophycean algal genera was extracted according to a protocol for the extraction of fungal DNA. Algal DNA was digested with up to ten different restriction endonucleases. In Southern hybridizations, DNA was probed with a digoxigenin-labelled 440 base pair (bp) fragment of bacteriophage M13 containing a repetitive sequence with a 15 bp core repeat. Stringency conditions for the detection of banding patterns in algae of different genera are described. The stability of DNA fingerprints of subcultures of the same isolate was investigated. DNA fingerprints of isolates of the genera Chlorella, Klebsormidium and Stichococcus were compared. The results show that the M13 minisatellite probe can be used to detect DNA fingerprints in chlorophyte algae of different genera and to differentiate isolates of the same species.