The high-quality genome of diploid strawberry (Fragaria nilgerrensis) provides new insights into anthocyanin accumulation.
Fragaria nilgerrensis is a wild diploid strawberry species endemic to east and southeast region in Asia and provides a rich source of genetic variations for strawberry improvement. Here, we present a chromosome-scale assembly of F. nilgerrensis using single-molecule real-time (SMRT) Pacific Biosciences sequencing and chromosome conformation capture (Hi-C) genome scaffolding. The genome assembly size was 270.3 Mb, with a contig N50 of ∼8.5 Mb. A total of 28,780 genes and 117.2 Mb of transposable elements were annotated for this genome. Next, detailed comparative genomics with the high-quality F. vesca reference genome was conducted to obtain the difference among transposable elements, SNPs, Indels, and so on. The genome size of F. nilgerrensis was enhanced by around 50 Mb relatively to F. vesca, which is mainly due to expansion of transposable elements. In comparison to the F. vesca genome, we identified 4,561,825 SNPs, 846,301 Indels, 4,243 inversions, 35,498 translocation, and 10,099 relocation. We also found a marked expansion of genes involved in phenylpropanoid biosynthesis, starch and sucrose metabolism, cyanoamino acid metabolism, plant-pathogen interaction, brassinosteroid biosynthesis, and plant hormone signal transduction in F. nilgerrensis, which may account for its specific phenotypes and considerable environmental adaptability. Interestingly, we found sequence variations in the upstream regulatory region of FnMYB10, a core transcriptional activator of anthocyanin biosynthesis, resulted in the low expression level of the FnMYB10 gene, which is likely responsible for white fruit phenotype of F. nilgerrensis. The high-quality F. nilgerrensis genome will be a valuable resource for biological research and comparative genomics research.