Screening Of SSR Markers From P.yezoensis And P.haitanensis And Their Applications On Analysis Of Genetic Polymorphism

P. yezoensis and P. haitanensis which show great values in academic research and economic development are the two most important kinds of marine algaes in China. It is very important to acquire enough knowledge on the genetic background of Porphyra to enlarge its cultivation scale and carry out research on genetic breeding of Porphyra.The experiment screens microsatellite sequences containing (GA)n and (CA)n, directly from genome of two species of Porphyra by establishing the enriched lirbrary. 62 positive clones which contain microsatellite DNA are obtained by situ-colony hybridization and PCR detection, of which 38 are from P. yezoensis and 24 are from P. haitanensis. And there are 64 microsatellite locuses in those 62 clones. There are 51 dinucleotide repeats and compound repeats whose repeating times is from 8 to 33, including 40 GA/CT repeats and 11 trinucleotide repeats and hexanucleotide repeats, which are all perfect types, accounting for 83% and 17%, respectively. Sequences analysis shows that there are more kinds of microsatellite motifs in P.yezoensis than that in P.haitanensis. All the trinucleotide and hexanucleotide repeats are from P.yezoensis. There are no much differences in the repeating times of motifs between two species of Porphyra.Thity-eight primers are designed and validated,25 of which can amplify PCR products with expected size. Sixteen are from P. haitanensis and 9 are from P. yezoensis. Fourteen sequences can not used to design primers because one of two flanking sequence is not long enough. Primer universalities analysis shows that 5 primers from P. yezoensis can be used in P. haitanensis and 9 from P. haitanensis can be used in P. yezoensis, which indicates the universality between two species is good.Finally,21 primers are used to study 11 pure lines of P. haitanensis and 18 primers are used to study the P. haitanensis samples from 4 different geographical populations. 25 locuses are abtained in P. hairanensis and 26 locuses are abtained in P. yezoensis. One primer can amplify polymorphic bands in P. haitanensis and another 2 amplify heterozygous bands; 6 primers amplify heterozygous bands in P. yezoensis among which there is 1 polymophic primer and the rest ones amplify homozygous bands also with 1 polymophic primer.The result indicates that genetic polymorphism among the materials is low. First, different lines of P. haitanensis are from the same cultivated line which may lead to little genetic variation. Secondly, even though the P. yezoensis samples are from different geographical populations, there may be much gene flow caused by ocean drift that passes the four places during the long history of evolution..