Developing a Molecular-Assisted Hybridization Strategy for the Improvement of the Quality of Poplar Biomass for the United States Bio-fuels Industry
This project was funded by the USDA-NIFA-Small Business Innovation Research Program. It was carried out from 2009 to 2011.
Black poplar (Populus nigra L.) is a primary candidate species for hybrid breeding programs focused on cellulosic ethanol production. Black poplar is naturally distributed across Europe, Northern Africa, and Asia and it is widely used as a parental to produce commercial hybrids (e.g. P.xcanadensis). However, a better understanding of genetic mechanisms underlying its chemical wood properties is needed to guide breeding efforts.
To identify associations between single nucleotide polymorphisms (SNPs)-markers within candidate genes encoding cellulose and lignin biosynthetic enzymes with phenotypic traits toward developing genomics based breeding technologies for bioethanol production.
An experimental population of 505 black poplar clones, representing 17 open pollinated families originating in European provenances was established in replicated clonal field trials at two locations contrasting in climate, soil, and management practices. Dramatic differences in growth were apparent between the two locations following the second year; a nearly three-fold difference was observed in height. Families originating in Italian provenances were superior for growth and biomass production compared with those of Belgian or Serbian origin. Clones from the Italian provenances were used for further association genetic analysis.
Wood samples were analyzed by pyrolysis molecular beam mass spectroscopy and phenotyped for total lignin content, content of five- and six-carbon sugars, and the ratio of syringyl-to-guacicyl monomeric forms of lignin. Biomass compositional traits were analyzed for components of genetic variance and in relationship to SNPs. The relationship between SNP polymorphisms present in a set of 39 candidate genes encoding proteins involved in the lignin and cellulose biosynthesis and the wood chemical phenotypes was assessed. A moderate to high heritability was observed for all traits. The LD, across all candidate genes, showed a rapid decay with physical distance. Analysis of single marker-phenotype associations identified six significant marker-trait pairs. On the other hand, near 280 haplotypes were associated with phenotypic traits, in both an individual and multiple trait-specific manner.