The complete chloroplast genome of paradox (Juglans major × J. regia), an interspecific hybrid in China.

Paradox is one of the most important rootstock resources in USA and China walnut industry. In this study, we characterized the complete chloroplast genome of Paradox (Juglans major × J. regia) based on next generation sequencing. The circular complete chloroplast genome was 160,324 bp in length, containing a large single-copy (LSC) region of 89,852 bp, and a small single-copy (SSC) region of 18,410 bp. These two regions were separated by a pair of inverted repeat regions (IRa and IRb) of 26,031 bp each. A total of 131 functional genes were encoded, consisted of 87 protein-coding genes, 36 tRNA genes, and 8 rRNA genes. The overall GC content of the chloroplast genome was 36.1% and the GC contents of the LSC, SSC, and IR regions were 33.7, 29.9, and 42.6%, respectively. The phylogenetic analysis by Neighbor-Joining showed that Paradox was relatively closely related to J. major compared to other species of Juglans genus. This complete chloroplast genome will provide valuable insight into evolution, molecular breeding, and phylogenetic analysis of Juglans species.