Molecular Phylogeny of the "True Citrus Fruit Trees" Group (Aurantioideae, Rutaceae) as Inferred from Chloroplast DNA Sequence

The genus Citrus L. has a long controversial taxonomy history, and a well-resolved molecular phylogeny of the "true citrus fruit trees" group in the future will provide new information for advancing breeding techniques and developing better conservation strategies. In the present study, three cpDNA fragments (TrnL-TrnF, PsbH-PetB, and TrnS-TrnG) of 30 genotypes chosen from the six genera of the "true citrus fruit trees" group were analyzed. A molecular phylogenetic tree of the "true citrus fruit trees" group was reconstructed based on plastid DNA sequences. The results confirmed that the "true citrus fruit trees" group was monophyletic, and thereby the group was divided into genera as previously suggested based on morphological characters. The cpDNA data also suggested that Poncirus might be the first genus separated from the other five genera in the group. The genus Fortunella were of hybrid origin and Citrus might be as its putative paternal parent. The genera Microcitrus, Eremocitrus, and Clymenia were possibly monophyletic and their common ancestor might branch out from Citrus. Furthermore, the phylogenetic relationships within the Citrus genus were discussed.