Identifying Molecular Markers Associated with Salt and Boron Tolerance in Poplar Trees

Some genotypes of poplar (Populus spp.) have a strong capacity for growth in soils with high salt (NaCl) and trace element contamination.  Using DNA from four salt/boron-tolerant and five salt/boron-sensitive genotypes of poplar, association linkages were discovered between DNA markers and salt/boron tolerance.

Use of polymorphic microsatellites allows genome-wide analysis of potential genetic elements linked to salt/boron tolerance in poplars.  Eighty-two polymorphic microsatellites widely distributed across 18 of the 19 poplar chromosomes were amplified and analyzed for size polymorphism. Scoring the markers for size polymorphism between accessions revealed 12 SSR markers linked to tolerance. Twenty-four primer pairs based on tolerance candidate genes from the literature were also analyzed. DNA sequencing yielded 9 markers that were tightly associated with salt/boron tolerance.

We have 62 additional primer pairs to test for linkage to the tolerance phenotype, 31 based on candidate genes and 31 based on proteins found by Danika LeDuc’s lab to be differentially expressed based on challenge with salt or boron.  An additional 20 of poplar genotypes have been obtained in order to increase our threshold of statistical significance.  They are currently being phenotyped and will be genotyped in the coming year. 

Poplar trees have good potential as high biomass producers for salt- and boron-contaminated soil that may otherwise lie fallow. Use of the newly discovered genetic markers in this project will help uncover the genetic basis for tolerance and could prove to be effective screening tools to identify additional tolerant poplar accessions best suited for growth in these soils.