Thimbleberry (Rubus parviflorus) is a shrub native to the western temperate regions of North America, from Alaska to California and the Rocky Mountains. Despite its ecological importance and broad native range, genomic information for this species remains extremely limited. So far, only one flow cytometry data point is available for thimbleberry, reporting a haploid nuclear DNA content (C value) of 0.28 pg, which suggests a haploid genome size of approximately 270 Mb. The Rubus genus exhibits a broad range of ploidy levels, such as from diploid to dodecaploid (2n = 2x = 14 to 2n = 12x = 84) for blackberries (R. argutus). Genome size variation has also been documented in other shrub species. In plants such as Chrysanthemum indicum, Linum suffruticosum, and Lycoris radiata, changes in ploidy levels have been associated with environmental stress. Given the wide native distribution of thimbleberry, we hypothesized that genome size variation may exist among different thimbleberry populations. The aim of this study was to estimate the genome size of eight thimbleberry populations collected from various locations across the United States, including the Northwest, Midwest, Southwest, and Rocky Mountains, using a flow cytometer. The findings from this study provide baseline genomic data that can support future research efforts, such as the construction of a reference genome and investigations into ploidy variation and its potential relationship with environmental stress tolerance.
