Towards Understanding and Harnessing Dosage Variation in Populus

Changes in gene dosage can affect gene function in multiple ways and inducing dosage mutations (insertions and deletions) is a powerful approach to rapidly creating wide phenotypic variation. This approach is rarely used in sexual species because the resulting variation is often meiotically unstable. In clonally propagated species, such as the fast growing tree species Populus, this approach holds many advantages. The dosage variants can be maintained vegetatively, clones can be produced to assess phenotypic consistency and some can be integrated in breeding programs rapidly if their performance warrants it. Using gamma irradiation of pollen grains, we have created a population of ~800 interspecific F1 sibling that vary in their chromosomal composition. Using low-pass whole genome sequencing, we characterized their genomic composition and found that approximately 50% of them carry at least one large-scale insertions or deletions across their genome. Within the population, the entire poplar genome is covered by on average 10 indel mutations, providing sufficient redundancy for effective functional genomic studies. Phenotypic characterization of this population is underway and will provide a powerful platform for both understanding gene function and the effect of gene dosage on phenotypes and on poplar hybrid performance. This resource is publicly available for others to investigate specific traits of interest.