Comparison of PCR-RFLP analysis of the ITS region with morphological criteria of various strains of Dunaliella

The genus Dunaliella comprises 28 species defined primarily by morphologica l and physiological criteria, which vary considerably depending on growth c onditions. Concomitantly, the taxonomic status of various species is uncert ain. To confirm the taxonomic identity and to better understand the relatio nship within Dunaliella, seven taxa (D. salina, D. bardawil, D. tertiolecta , D. parva, D. viridis, D. lateralis, D. peircei) were compared using RFLP analysis of the nuclear rDNA repeats, specifically the internal transcribed spacer regions, including the 5.8S rRNA gene. Volvox aureus was used as an outgroup. A single ITS PCR amplification product was obtained for each tax on. An ITS fragment of ca. 640 bp was present in all the taxa within the su bgenus Dunaliella, except for D. salina CCMP 1303 (ca. 540 bp) and D. later alis (subgenus Pascheria) (ca. 600 bp). A cluster analysis based on the pre sence or absence of bands generated by digestion of the PCR product with 8 restriction endonucleases (DpnI, HhaI, EcoRI, PVuII, TaqI, HaeIII, MspI, St yI) revealed no correlation between the genetic relationship inferred from the ITS-RFLP data and the morpho-physiological attributes used for taxonomy . In addition, differences in morphology, physiology and in the length and restriction fragment patterns of the ITS region of D. salina CCMP 1303 sugg est that this strain does not belong to Dunaliella.