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Pak. J. Bot., 47(1): 95-101, 2015.

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Taxonomy and phylogeny of the genus Citrus based on the  nuclear ribosomal DNA ITS region sequence

Yan-Lin Sun^1*, Ho-Min Kang², Sang-Heon Han³, Young-Chul Park⁴  AND Soon-Kwan Hong^{5, 6}*

Abstract: The genus Citrus (Aurantioideae, Rutaceae) is the sole source of the citrus fruits of commerce showing high economic values. In this study, the taxonomy and phylogeny of Citrus species is evaluated using sequence analysis of the ITS region of nrDNA. This study is based on 26 plants materials belonging to 22 Citrus species having wild, domesticated, and cultivated species. Through DNA alignment of the ITS sequence, ITS1 and ITS2 regions showed relatively high variations of sequence length and nucleotide among these Citrus species. According to previous six-tribe discrimination theory by Swingle and Reece, the grouping in our ITS phylogenetic tree reconstructed by ITS sequences was not related to tribe discrimination but species discrimination. However, the molecular analysis could provide more information on citrus taxonomy. Combined with ITS sequences of other subgenera in the “true citrus fruit tree” group, the ITS phylogenetic tree indicated subgenera Citrus was monophyletic and nearer to Fortunella, Poncirus, and Clymenia compared to Microcitrus and Eremocitrus. Abundant sequence variations of the ITS region shown in this study would help species identification and tribe differentiation of the genus Citrus.

Key words: Citrus; Phylogenetic relationship; ITS region; Genetic diversity.

¹School of Life Sciences, Ludong University, Yantai, Shandong, 264-025, China

²Department of Horticulture, Kangwon National University, Chuncheon, 200-701, Korea

³Faculty of Bioscience & Industry, Jeju National University, 66 Jejudaehakno Jeju-si Jeju Special Self-governing Province, 690-756, Korea

⁴Jeju Special Self-governing Province Agricultural Research and Extension Services 212, Jungsangan seoro,

Seogwipo-si, Jeju Special Self-governing Province, 697-828, Korea

⁵Deaprtment of Bio-Health Technology, Kangwon National University, Chuncheon, 200-701, Korea

⁶Institute of Bioscience and Biotechnology, College of Biomedical Science, Kangwon National University,

Chuncheon, 200-701, Korea

*Corresponding author. E-mail: laddiya@hotmail.com (YL Sun); soonkwan@kangwon.ac.kr (SK Hong); Tel.:86-535-6685003 (YL Sun); 82-33-250-6476 (SK Hong); Fax: 82-33-250-6470 (SK Hong)