Genetic variation among seven strains of Dunaliella salina (Chlorophyta) with industrial potential, based on RAPD banding patterns and on nuclear ITS rDNA sequences

Abstract

Dunaliella salina (Chlorophyta) is a halophilic microalga cultivated as a natural source of β-carotene in several countries, including Chile. Previous studies of some Chilean strains of this microalga have shown a great variability in their physiological and genetic attributes. Random amplified polymorphic DNA (RAPD) band patterns and nuclear ribosomal DNA internal transcribed spacer (ITS-1 and ITS-2) sequences were used to genotypically characterize three Chilean and four foreign (from Mexico, China, Australia and Israel) strains of D. salina with industrial potential. Unweighted pair group mean average (UPGMA) cluster analysis of RAPD data distinguished, at 70% similarity, two clusters. One cluster included all of the foreign strains, except the one from Australia, and the other grouped two of the Chilean strains (CONC-001 and CONC-007). The other Chilean strain (CONC-006) and the Australian strain appeared as single entities. Neighbor-joining (NJ), maximum parsimony (MP) and maximum likelihood (ML) analyses of the ITS sequence data yielded four clades, most of them well supported: there were two clades containing exclusively one strain, CONC-006 from Chile (86–94% support) and the one from Australia (98–100% support); the third clade grouped the strains from Mexico, China and Israel (99–100% support), and, the fourth clade, the strains CONC-001 and CONC-007 from Chile (100% support). Both RAPD banding pattern and ITS sequence data were consistent in resolving the same genetic relatedness among the strains analyzed. For both approaches, the strain CONC-006 from Chile and the strain from Australia were the most divergent entities within the group. Furthermore, the strain CONC-006 appeared genetically more related to the foreign strains than to the other Chilean ones. The physiological attributes exhibited by these strains of D. salina are mostly in agreement with the genetic relationships deduced from this study.