Phylogenetic Studies Of Yellow Camellias Based On Chloroplast Small Single Copy (SSC) Sequence

Yellow Camellias are group of the famous ornamental plants honored as "The Queen of Camellia" for having yellow, waxy and shiny petals. As Chinese important germplasm resources, Yellow Camellias have an important economic and scientific value in the cultivation of new varieties and the development of drug and health care products. At present, China have published more than thirty yellow Camellias, however, the classifications from different researchers are inconsistent. Many researchers have tried to use morphology and molecular evidence to solve the problem, but the evidence is scattered, and the species involved are not comprehensive. In this study, We use the chloroplast small single copy (SSC) sequence to reveal the phylogenetic relationships about yellow Camellias, and provide insight for classification and conservation of yellow Camellias. Conclusions are the following:(1) The length varied from 18,235 bp to 18,286 bp in the SSC region, The SSC region contained 14 genes:ndhF, rpl32, trnL-UAG, ccsA, ndhD,psaC, ndhE, ndhG, ndhl, ndhA, orf188, ndhH, rps15 and ycf1; The SSC sequences show highly A+T bias (69.4%); The average content of each base composition is:A (34.6%), T(34.8%), G(14.5%), C(16.1%).(2) The phylogenetic trees(BI, MP and NJ) show that:all yellow Camellias can be divided into five branches, the composition and structure are basically consistent and well supported: Clade I (PP=1.00/99.6/99.6), Clade II (PP=1.00/99.7/100.0), Clade III (PP=1.00/94.7/98.4), Clade IV (PP=1.00/96.5/94.7), Clade V (PP=1.00/90.8/93.3). The geographic distribution and genetic relationship are basically consistent. C. Chrysantha, C. nitidissima var. Microcarpa, C. quinqueloculosa, C. multipetala var. patens, C. multipetala and C. wumingensis form the Clade Ⅰ, mainly distribute in Nanning, Fusui, Chongzuo and Wu Ming; Inside the branch, there is also a closed relationship between phylogenetic relationship and geographical distribution, C. nitidissima var. Microcarpa (Nanning) and C. chrysantha (Tanluo and Fusui population) are classified into a small group, C. quinqueloculosa, C. multipetala var. patens, C. multipetala (all from Fusui population) are classified into the second small group, C. wumingensis which distribute in Wuming forms the third group. C. nitidissima, C. tunghinensis and C. euphlebia are classified into the Clade II, mainly distribute in the south of Shiwan Mountain of Fangcheng. C. micrantha, C. xiashiensis, C. ptilosperma, C. chrysanthoid.es and C. parvipetala form the Clade III, mainly distribute in Ningming. In the Clade IV, there are C. huana, C. tianeensis, C. pubipetala and C. pingguoensis var. terminalis, these species mainly distribute in Guizhou, TianE, TianDeng, LongAn and Daxin; in this branch, C. huana and C. tianeensis (which come from Guizhou and TianE of Guangxi respectively) form a small group, C. pubipetala and C. pingguoensis var. terminalis are classified into the other group, these two species mainly come from TianDeng, LongAn and Daxin of Guangxi. C.flavida, C.impressinervis, C. longgangensis, C. grandis, C. longruiensis and C. longzhouensis are classified into the Clade V, mainly distribute in Longzhou. In addition, C. fascicularis from Yunan has a distant kinship with other species of Camellia. C. murauchii, C. hirsuta and C. amplexicaulis from Vietnam are closely related to each other.But not all species who have the same or similar distribution are classified into a group, such as, C. liomonia is not classified into the Clade V, C. achrysantha from Fusui is not classified into the Clade I.(3) Internal relationship of each branch is analyzed, and the results indicate that C. micrantha, C. xiashiensis and C. parvipetala are closely related to C. chrysanthoides, they should be merged into C. chrysanthoides. For C. ptilosperma, the chloroplast sequence shows that C. ptilosperma has a closed relationship with C.chrysanthoides, but the ITS sequence reveals that C. ptilosperma and C. flavida are closely related and probably conspecific, suggesting it may be the offspring of hybridization from C.chrysanthoides and C. flavida. C. longzhouensis is highly divergent from C.chrysanthoides, but it has a closed relationship with C. flavida, C. longgangensis, C. grandis and C. longruiensis, they should be merged into C. flavida; C. pingguoensis var. terminalis is highly divergent from C. pingguoensis. C. liberofilamenta is a distinctive species. C. huana and C. tianeensis are closely related and probably conspecific. C. quinqueloculosa, C. multipetala var. patens and C. multipetala are closely related and probably conspecific, while C. wumingensis has a distant relationship with these taxa, it should be a distinctive species; C. chuongtsoensis and C. perpetua are closely related and probably con-specific.