Assembly and comparative analysis of the complete mitochondrial genome of Lactuca sativa var. ramosa Hort.

Lettuce (Lactuca sativa var. ramosa Hort) is an important leaf vegetable that widely cultivates due to its high-quality, short growth cycle, and less diseases. L. sativa var. ramosa Hort belongs to Asteraceae family and its evolutionary relationships with related species of Asteraceae are not completely assessed based on genome sequences. Here, we assembled the whole mitochondrial (mt) genome of L. sativa var. ramosa Hort, and performed a comparative with other related species. The L. sativa var. ramosa Hort mt genome has a typical circular structure with a length of 363,324 bp, within GC content accounted for 45.35%. In total of 71 genes, comprising 35 protein-coding genes (PCGs), 6 rRNAs, 28 tRNAs, and 2 pseudogenes were annotated. Codon preference, RNA-editing sites, repetitive sequences, and genes migrating from chloroplast (cp) to mt genomes were investigated in the L. sativa var. ramosa Hort mt genome. Nucleotide diversity (Pi) showed that the L. sativa var. ramosa Hort mt genome was relatively conserved. A Bayesian phylogenetic tree showed that L. sativa var. ramosa Hort was closely to L. sativa var. capitata and L. virosa, which belonged to the Lactuca genus in the Asteraceae family. Our findings will provide useful information to explore genetic variation, genetic diversity, and molecular breeding on the Lactuca genus.