Genetic Diversity of Dianthus Plants Revealed by SRAP Markers

Dianthus is a valuable genetic resource for flower breeding. However, study on the genetic similarity of Dianthus plants is rare. In this work, 20 pairs of SRAP markers were used to analyze genetic diversity of 44 Dianthus plants, including 13 lines of wild Dianthus chinensis L., 7 lines of wild Dianthus superbus L. and 24 commercial varieties including Dianthus caryophyllus L., Dianthus plumarius L. and Dianthus barbatus L.. Results showed that precise interspecific and intraspecific genetic diversity was provided in Dianthus plants by using 20 pairs of SRAP molecular markers. The interspecific genetic diversity of Dianthus plants was much abundant and the intraspecific genetic difference of wild Dianthus species was related to their geographical distribution and habitats. In this work, theoretical basis and technical support were provided for crossbreeding and molecular mechanism research of Dianthus plants.


Introduction
Dianthus plants are herbs in Caryophyllaceae. About 600 kinds of Dianthus species are recorded 27 worldwide, most originated in Europe and Asia, and a few in America and Africa. In China, there are 17 28 species, 1 subspecies and 9 variants, most of which are grown in the northern grassland and mountainous 29 grassland [1,2]. Dianthus plants all have very significant application value because of their colorful flowers, 30 long flowering period, air purification ability, adaptability to abiotic stress, and so on. Dianthus caryophyllus 31 L. is one of the four major cut flowers worldwide and plays an important role in the flower market [3]. 32 Dianthus plumarius L. is an important environmental protection and greening plant, because of its strong 33 reproductive capacity and rapid growth speed which can effectively prevent soil erosion and soil erosion 34 [4][5][6]. Dianthus chinensis L. and Dianthus Superbus L. are used as herbal medicine for its function of 35 reducing fever and diuresis, and also as insecticidal pesticides [7][8][9]. Dianthus barbatus L. is also an 36 important source of cut flowers and a greening plant. It can purify the air by absorbing harmful gases such as 37 sulfur dioxide and chlorine [10]. Therefore, Dianthus is a valuable genetic resource for flower breeding.

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It is a common breeding strategy to improve plant characters for Dianthus to by aggregating excellent 39 traits from different species through interspecific hybridization [11,12] plumarius L. and Dianthus barbatus L. (Table S1). Collection area information of wild species was given in 56  Table S2.

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Young-leaf tissue from samples was ground in liquid nitrogen to a fine powder and total genomic DNA 59 was extracted using the modified CTAB method. DNA quality testing was performed by 1% agarose gel 60 electrophoresis.

SRAP Analysis
62 88 primer pairs were used in this work which consisted of 8 forward primers and 11 reverse primers.

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DNA Extraction and Testing of PCR Products. 82 Genomic DNA was showed clear bands and undegraded extracted by modified CTAB method which 83 mean the DNA was qualified for genotyping (Fig 1a). Only 20 primer pairs in 88 pairs were amplified 84 successfully (Table 2, Fig 1b).   (Table S3).

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In this work, 414 polymorphic bands were used for genetic similarity analysis. The Jaccardp's similarity 99 coefficient ranged from 0.73 to 0.98. 44 samples were divided into 5 groups which were in accordance with 9 100 the species (Fig 2). In these 5 groups, Dianthus plumarius L. showed the minimum genetic similarity with 101 other four species, and the second and the third were Dianthus caryophyllus L. and Dianthus barbatus L.
102 respectively (Fig 2). In wild species, the intraspecific genetic similarity was strongly associated with the habitat.  (Fig 2). The first and the second subgroup located in low latitude showed a higher genetic 120 similarity than the third one located in high latitude (Fig 2, Table S1).Similarly, the wild Dianthus superbus 121 L. group was also divided into 2 subgroups, one in the south Shanxi Province including 38/39/43 and another 10 122 in north-central Shanxi Province including 40/41/42/44 (Fig 2, Table S1). In this work, the intraspecific 123 genetic similarity of wild species was closely related to their geographical distribution and habitats. And the 124 intraspecific genetic similarity of cultivars showed a high relationship with their phenotypic characteristics.

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For example, Dianthus barbatus L. group was divided into 2 subgroups, one including 1/2/3/4/5/6/7 and 126 another including 16/17. The forward could also be divided into 2 groups, pink flower group including and 127 white/red flower group. Furthermore, the pink flower group could also be divided into 2 groups, light pink 128 and dark pink.

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In conclusion, the interspecific genetic diversity of Dianthus plants was much abundant and the 130 intraspecific genetic difference of wild Dianthus species was related to their geographical distribution and 131 habitats. Precise interspecific and intraspecific genetic diversity was provided in Dianthus plants by using 132 SRAP molecular markers. In this work, theoretical basis and technical support were provided for 133 crossbreeding and molecular mechanism research of Dianthus plants.