Research On Genetic Diversity And Taxonomic Status Of Betula Microphylla Bunge Var. Ebinurica Natural Populations

Betula microphylla Bunge var. ebinurica is dungarunga of Betula Linn. of Betulaceae. Grows in Jinghe County, located in front of the mountains in the desert, shallow marshes, forming small woodlot. In order to reveal the genetic diversity and genetic structure of rare plant Betula microphylla Bunge var. ebinurica, provide a theoretical basis for the protection, this study analyze the genetic diversity and genetic structure of four natural populations using ISSR molecular marker. In order to further confirm the phylogenetic taxonomic status of Betula microphylla Bunge var. ebinurica on Betula species in Xinjiang on molecular level, this study analyze the interspecific relationship of major Betula species existing in Xinjiang using ISSR molecular marker. Analyze the interspecific relationship among Betula microphylla Bunge var. ebinurica, Betula pendula Roth., Betula humilis Schrank and Betula tianschanica Rupr.. The results are as follows:(1)Establish and optimize the ISSR reaction system of Betula species: 20μl reaction volume, concentration of Mg2+ is 1.65 mmol·L-1, concentration of dNTPs is 0.35 mmol·L-1, concentration of primer is 0.5 μmol·L-1, template DNA is about 25 ng, Taq DNA Polymerase is 1U, other ingredient of it is double-distilled water;(2)Analyze the genetic diversity of Betula microphylla Bunge var. ebinurica natural populations using ISSR molecular marker. Screen out 12 ISSR primers for PCR amplification of 40 individuals of four Betula microphylla Bunge var. ebinurica natural populations. 122 bands were amplified, of which 102 are polymorphic bands. The percentage of polymorphic bands is 83.61%. Nei’s gene diversity index at the species level is 0.2850, and at the population level is 0.2373. Shannon’s information index at the species level is 0.4304, and at the population level is 0.3504. It indicates the genetic diversity of Betula microphylla Bunge var. ebinurica natural populations is high. The coefficient of gene differentiation of four natural populations is 0.1673. AMOVA analysis measures that the variation among populations account for 12.63% of the total variation, showing that the majority of genetic differentiation of Betula microphylla Bunge var. ebinurica natural populations majority exists within populations. The gene flow among populations is high(Nm = 2.4891);(3)Analyze the interspecific relationship among Betula microphylla Bunge var. ebinurica, Betula pendula Roth., Betula humilis Schrank and Betula tianschanica Rupr. using ISSR molecular marker. Screen out 12 ISSR primers for PCR amplification of 76 individuals of five birch populations. 139 bands were amplified, of which 130 are polymorphic bands. The percentage of polymorphic bands is 93.53%. When comparing Betula microphylla Bunge var. ebinurica with other birch populations, the genetic identity is the largest(0.9185) between Betula microphylla Bunge var. ebinurica populations and Betula tianschanica Rupr. populations, the smallest(0.7450) between Betula microphylla Bunge var. ebinurica populations and Betula pendula Roth. 1 populations. Use UPGMA(unweighted pair-group method with arithmetic means) for cluster analysis. It turns out Betula microphylla Bunge var. ebinurica and Betula tianschanica Rupr. cluster into one group firstly, then with Betula humilis Schrank clustering together. Two Betula pendula Roth. populations cluster together, and then cluster together with other three birch populations. It indicates that the genetic relationship is nearer between Betula microphylla Bunge var. ebinurica and Betula tianschanica Rupr.. The results obtained by molecular markers is consistent with traditional taxonomy results.