Abstract
BACKGROUND: Pitaya is an important tropical fruit highly favoured by consumers owing to its good and juicy characteristics. It contains a large amount of betacyanin, which is a natural food-colouring agent, in the peel and pulp. However, few studies have focused on the pitaya chloroplast (cp) genomes. RESULTS: To explore the genetic differences and phylogenetic relationships among the cp genomes of the six pitaya cultivars, we assembled, annotated, and performed a comparative genomic analysis. The cp genomes of the six cultivars exhibited a typical circular structure, ranging in length from 133,146 to 133,617 bp, with a GC content of 36.4%. All individual cp genomes were annotated with 123 genes, including 80 protein-coding genes, 38 tRNA genes, four rRNA genes, and one pseudogene (ycf68). Six mutated hotspot regions (trnF-GAA-rbcL, trnM-CAU-accD, rpl20-psbB, accD, rpl22, ycf1) were detected, which could be considered potential molecular markers for population genetics and molecular phylogeny studies. Phylogenetic analysis showed that pitaya cultivars clustered into a single branch in the phylogenetic tree of the Cactaceae family. Furthermore, the observed phylogenetic patterns suggest a complex genetic basis for colour variation among pitaya cultivars. CONCLUSIONS: The study findings expand our understanding of the cp genome of pitaya and the phylogenetic relationships among different cultivars. The genomic data obtained provide important information for the breeding and genetic improvement of pitaya.