A high-quality chromosome-scale genome assembly of blood orange, an important pigmented sweet orange variety

Abstract

Blood orange (BO) is a rare red-fleshed sweet orange (SWO) with a high anthocyanin content and is associated with numerous health-related benefits. Here, we reported a high-quality chromosome-scale genome assembly for Neixiu (NX) BO, reaching 336.63 Mb in length with contig and scaffold N50 values of 30.6 Mb. Furthermore, 96% of the assembled sequences were successfully anchored to 9 pseudo-chromosomes. The genome assembly also revealed the presence of 37.87% transposon elements and 7.64% tandem repeats, and the annotation of 30,395 protein-coding genes. A high level of genome synteny was observed between BO and SWO, further supporting their genetic similarity. The speciation event that gave rise to the Citrus species predated the duplication event found within them. The genome-wide variation between NX and SWO was also compared. This first high-quality BO genome will serve as a fundamental basis for future studies on functional genomics and genome evolution.