Chloroplast genome assemblies and comparative analyses of commercially important Vaccinium berry crops

Abstract

Vaccinium is a large genus of shrubs that includes a handful of economically important berry crops. Given the numerous hybridizations and polyploidization events, the taxonomy of this genus has remained the subject of long debate. In addition, berries and berry-based products are liable to adulteration, either fraudulent or unintentional due to misidentification of species. The availability of more genomic information could help achieve higher phylogenetic resolution for the genus, provide molecular markers for berry crops identification, and a framework for efficient genetic engineering of chloroplasts. Therefore, in this study we assembled five Vaccinium chloroplast sequences representing the economically relevant berry types: northern highbush blueberry (V. corymbosum), southern highbush blueberry (V. corymbosum hybrids), rabbiteye blueberry (V. virgatum), lowbush blueberry (V. angustifolium), and bilberry (V. myrtillus). Comparative analyses showed that the Vaccinium chloroplast genomes exhibited an overall highly conserved synteny and sequence identity among them. Polymorphic regions included the expansion/contraction of inverted repeats, gene copy number variation, simple sequence repeats, indels, and single nucleotide polymorphisms. Based on their in silico discrimination power, we suggested variants that could be developed into molecular markers for berry crops identification. Phylogenetic analysis revealed multiple origins of highbush blueberry plastomes, likely due to the hybridization events that occurred during northern and southern highbush blueberry domestication.