| As one of leading constructive species in Yellow River Delta, Tamarix chinensis plays an important role on maintaining wetland ecological balance. To better understand the population genetic structure and evolutionary dynamic of local T. chinensis, five populations of T. chinensis in Yellow River Delta distributing in different habitats with variable soil salinity were investigated using inter-simple sequence repeat (ISSR) markers. The genetic diversity, the genetic differentiation indexes within and among populations, and the correlation between the population genetic structure and soil salinity were further compared and analyzed. The main results are as follows.1. Optimization of ISSR-PCR reaction system and amplified procedureWe optimized the reaction system and amplified procedure for T. chinensis, which was 25μL amplification reactions system containing 10×PCR Buffer 2.5μL,2 mM Mg2+, dNTP 0.2 mM, 0.4 pM primers,10 ng template DNA,1 unit of Taq DNA polymerase. The PCR amplified procedures was as follows:after a pre-denaturing of 5 min at 94℃, then 39 cycles of 1 min at 94℃for denaturation,1 min at a primer-appropriate temperature for annealing,2 min at 72℃for extension, and a final step of 10 min elongation at 72℃.2. Ten effective ISSR-PCR primers were selected from 100 ISSR primers.3. Obtainment of the information about the genetic diversities and population structure of T. chinensis in the Yellow River DeltaUsing Inter Simple Sequence Repeat (ISSR) markers, five populations of T. chinensis, which consisted of 140 individuals, were analyzed in this study. Seventy-eight polymerase chain reaction fragments were scored, out of which 62 were polymorphic. The mean percentage of polymorphic loci (P) was79.5%, the number of alleles per locus (A) was 1.775±0.420, the effective number of alleles per locus (AE) was 1.398±0.347, and the mean Nei's gene diversity (h) and the mean Shannon's information index (I)were 0.239±0.187and 0.363±0.264, respectively. These indexes indicated that a moderate level of genetic diversities existed in T. chinensis populations of the Yellow River Delta. At the population level, however, a lower level of genetic diversity (P=56.3%;A=1.563±0.497;AE=1.322±0.367;h=0.190±0.198; I=0.285±0.283) was revealed. Among the five populations, the highest genetic diversities were found in both BHZX and YDD populations, and the lowest genetic diversity was obtained in HHK population.The genetic differentiation coefficient Gst in present study was 0.159, which demonstrated that 15.9% of genetic variability existed among the T. chinensis populations. The estimated average number of migrants among populations (Nm) deduced by Gst was 2.637, implying a high level of gene flow exchanged among populations, which might be one reason for the less genetic differentiation among populations. Analysis of molecular variance (AMOVA) also revealed that most of the genetic variance (83.1%) of T. chinensis occurred within populations.Unweighted pair group method with arithmetic mean (UPGMA) and showed that the populations with similar soil salinity had a close relationship, rather than the populations with a closer geographical distance. The mantel test showed that there was no correlation between genetic distance and geographical distance (r=-0.127, p>0.05), but A significant negative correlation between genetic diversity and soil salinity of 5 populations (r=-0.958, p=0.005) was displayed. This result showed that soil salinity played an important role in shaping the population genetic structure of T. chinensis in the Yellow River Delta. |
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