Eleven million raw reads were generated from sequencing and trimmed using Trimmomatic v0.35 to produce low quality reads. All sequenced plant mitochondrial genomes were downloaded from NCBI and used as a local blast database. To minimize the possibility of contaminated reads from plastid or nuclear genomes, filtered reads were first mapped to the local database and mapped reads were subsequently imported into Geneious v10.1.3 (Biomatters, Inc., Auckland, New Zealand; http://www.geneious.com) for initial assembly. The contigs generated by the initial assembly were used as seeds for further iterative mapping and extension processes. Velvet and Geneious were alternatively used during assembly with multiple combinations of k-mer lengths.