Genetic diversity and molecular phylogeny of Planktothrix (Oscillatoriales, cyanobacteria) strains from China

The genus Planktothrix Anagnostidis et Komárek 1988 represents an important, water-bloom forming cyanobacterial group, and in recent years it has been found to occur in dense water blooms around China. In this study, genetic diversity and phylogeny of Planktothrix strains isolated from seventeen Chinese water bodies, based on 16S rRNA, rbcLX and rpoC1 genes, were investigated. These Planktothrix strains, all phycocyanin-containing, were morphologically classified into two groups as Planktothrix agardhii and Planktothrix mougeotii. However, phylogenetic analyses, based on the three gene regions, revealed that Planktothrix strains analyzed in this study were mainly divided into three clades, corresponding to P. agardhii, Planktothrix pseudagardhii, and P. mougeotii respectively. The strains in the P. pseudagardhii clade were shown to be more genetically divergent, reflecting possible existence of cryptic species in the genus Planktothrix.