Thesis

Microsatellite markers for salt/boron tolerance in poplar trees

The poplar tree (Populus trichocarpa) has a strong capacity for growth in regions with high salt and trace element contamination in the soil. Using DNA from three salt/boron tolerant and six sensitive genotypes of poplar, association linkages are discovered between DNA markers and the polygenic trait of salt/boron tolerance. A set of 82 primer pairs was developed from previous research, flanking SSR (simple sequence repeat) regions on 18 of the 19 poplar chromosomes. Microsatellites from each of the nine poplar clones were amplified and detected using polyacrylamide gel electrophoresis. Scoring the markers for size polymorphism between accessions revealed SSR markers linked to the tolerant/intolerant phenotype. Polymorphism data allowed inference of relatedness of the accessions based on genetic similarity, as well as better characterization of SSR polymorphic frequency in the poplar genome. Mapping the markers on the poplar genome gives insight as to salt/boron tolerance-contributing regions of the genome. Using the results, a map of 12 microsatellite markers that are linked to salt and boron tolerance in poplars was established, which could prove to be an effective screening method to identify additional tolerant poplar accessions. Microsatellite regions analyzed were nearly all polymorphic (95.5%), showing no correlation between SSR location and polymorphism rate. Use of polymorphic microsatellites allowed genome wide analysis of genetic elements linked to salt/boron tolerance in poplars.

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