Characterization of chloroplast matK sequences of Citrus tachibana and Citrus depressa, two indigenous species in Japan

Citrus tachibana, C. nippokoreana, and C. depressa are indigenous mandarin species in Japan. We deduced their phylogenetic relationships from nucleotide sequences of the chloroplast matK gene. The results indicate that C. tachibana, C. nippokoreana, and C. depressa accessions can be classified into two types: type A, all sixteen C. tachibana and six C. Depressa; type B, eleven C. depressa and one C. nippokoreana. Both type A and type B accessions of C. depressa were found on the Okinawa Islands, whereas only type B accessions of C. depressa were found on the Sakishima and Amami Islands. This cpDNA divergence seemed to indicate a polyphyletic origin of C. depressa. The matK genes of type A were found only in C. tachibana and some C. depressa. From these results, both species probably possess a characteristic chloroplast genome among various Citrus species