The comparative chloroplast genomic analysis of photosynthetic orchids and developing DNA markers to distinguish Phalaenopsis orchids

The chloroplast genome of . Phalaenopsis equestris was determined and compared to those of . Phalaenopsis aphrodite and . Oncidium Gower Ramsey in Orchidaceae. The chloroplast genome of . P. equestris is 148,959. bp, and a pair of inverted repeats (25,846. bp) separates the genome into large single-copy (85,967. bp) and small single-copy (11,300. bp) regions. The genome encodes 109 genes, including 4 rRNA, 30 tRNA and 75 protein-coding genes, but loses four . ndh genes (. ndhA, . E, . F and . H) and seven other . ndh genes are pseudogenes. The rate of inter-species variation between the two moth orchids was 0.74% (1107 sites) for single nucleotide substitution and 0.24% for insertions (161 sites; 1388. bp) and deletions (189 sites; 1393. bp). The IR regions have a lower rate of nucleotide substitution (3.5-5.8-fold) and indels (4.3-7.1-fold) than single-copy regions. The intergenic spacers are the most divergent, and based on the length variation of the three intergenic spacers, 11 native . Phalaenopsis orchids could be successfully distinguished. The coding genes, IR junction and RNA editing sites are relatively more conserved between the two moth orchids than between those of . Phalaenopsis and . Oncidium spp.