Functional Genomics of Poplar Bioenergy Phenotypes Using a Unique Dosage Variants Population

Poplars are among the fastest growing temperate trees in the world, with important ecological and economic value, including the production of biofuels and other value-added products. The poplar clones with the highest biomass yield are created through hybridization between species. Superior hybrid performance is believed to result in part from interactions among genomic regions that are in different copy number in the two species. Nevertheless the role of gene dosage in producing superior commercial hybrid poplar cultivars is not fully understood or effectively manipulated. We have produced a population of interspecific poplar hybrids carrying large-scale insertions and deletions (dosage lesions) scattered over the entire poplar genome. Dosage lesions were detected in approximately 55% of the progeny, and varied in length, position and number per individual, with a mean number of 2.4 lesions/individual and an average length of 5.7 Mb/lesion. Cumulatively, these lesions cover >99% of the genome with an average of 10 lesions affecting each gene. This population has been characterized for phenotypic traits related to biomass production, leaf morphology, wood properties and drought tolerance. Identification of genotypes displaying transgressive variation for specific traits will be described, as well as analyses seeking associations of phenotypic traits with genomic regions. Overall our study supports a better understanding of the role of gene dosage in poplar hybrid performance, and the identification of genes and genetic mechanisms contributing to poplar bioenergy traits. Additionally, since poplar trees can be clonally propagated, superior hybrid lines identified in this study are directly relevant to the industry.