Conventional identification of three coccoid green algae isolates was attempted to characterize the studied algae morphologically under compound microscope, which demonstrated confusional phenomenal convergence; all were classified microscopically as the green alga Chlorella vulgaris Beijerinck, 1890.
Phylogenetic studies were conducted to settle the argument about the phenotype by studying the genotype. Genotype the promising field in advance classification by using 18S rRNA and compared to GenBank database using to search the related sequences. The determined sequences showed high a similarity to the strains registered in GenBank.
Phylogenetic tree of ITS within 18S RNA were analyzed: the phylogram separated into two clusters, the first cluster included C1-ITS-Iraq and C2-ITS-Iraq and put with Coelastrella Chodat, 1922 which was well supported in bootstrap tests (86-100%), while the second cluster included C3-ITS-Iraq and put with C. sorokiniana Shihira and Krauss, 1965, which have bootstrap value 100% with the mentioned species. however, in this study, the green alga Colestrella was identified as new record genus in Iraqi freshwater belonged to the order Sphaeropleales.
