Genetic Analysis Of The Cultivated Strains Of Laminaria And Gracilaria

The genetic diversities of two important economic seaweeds (Laminaria and Gracilaria) were analyzed in order to find out the molecular markers relating to excellent economic characters. And the phylogenetic trees were constructed based on the genetic diversities. The internal transcribed spacer (ITS) regions of nuclear ribosomal DNA (including 5.8 S rDNA) of 6 Laminaria cultivars (CUL002, CUL860, CUL1170, CUL901, CUL018) with clear genetic backgrounds and variant phenotypes, as well as L. longissima planted in China were amplified and sequenced. The phylogenetic relationships of 7 Laminaria spp. together with 10 selected groups (representing 7 Laminaria species) and Undaria peterseniana downloaded from GenBank were constructed based on ITS and 5.8 S rDNA sequences. Undaria peterseniana was designated as outgroup. The results indicated that: (1) there was little diversity in ITS regions of 6 Laminaria cultivars. The ITS1+5.8 S rDNA sequences were exactly the same as that of L. Japonica (AF319018, Japan), however, the ITS2 regions possessed individual variations. Futhermore, the ITS + 5.8 S rDNA sequences of CUL901, CUL860 and CUL1170 were identical. (2) The ITS and 5.8 S rDNA sequence of L. longissima was identical to that of L. japonica (AF319018, Japan), and it was supposed to be a morphologic variation of L. japonica. The ITS + 5.8 S rDNA-based phylogenetic tree showed that: 14 selected Laminaria strains were divided into 2 strongly-supported monophyletic clades. Gracilaria asiatica and 5 G. lemaneiformis strains were analyzed by random amplified polymorphic DNA (RAPD) to determine the phylogenetic relationships. 7 highly polymorphic primers were screened from fifty 10-base primers and amplified 74 polymorphic DNA bands. Based on RAPD patterns, the genetic similarities and distance were calculated according to Nei coefficient using PhylTools. The phylogenetic analysis was performed by software TFPGA and PHYLIP using UPGMA clustering method as well as neighbor-joining and Wagner (Mixed Parsimony) method. The results indicated that: (1) the diversities of genomic DNA among Gracilaria taxa were much higher than that within G. lemaneiformis taxon, and differed distinctly among different strains of G. lemaneiformis. (2) G.asiatica rooted in all phylogenetic trees. The similarities between G.asiatica and G. lemaneiformis strains averaged at 0.278. (3) In G. lemaneiformis taxon, there were close phylogenetic relationships between the Qingdao wild strain, the Fujian cultivar and the Lianyungang cultivar. The Fujian cultivar was the closest relative to Lianyungang one and the similarity between them was 0.875. The genomic diversity of the Guangdong cultivar was the highest and the similarity averaged at 0.491 in comparison with other cultivars.