Moderate Genetic Diversity and Genetic Differentiation in the Relict Tree Liquidambar formosana Hance Revealed by Genic Simple Sequence Repeat Markers

作   者：Rongxi Sun , Furong Lin , Ping Huang and Yongqi Zheng
期刊名称：Frontiers in Plant Science
影响因子：4.298
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论文摘要：
Chinese sweetgum (Liquidambar formosana) is a relatively fast-growing ecological
pioneer species. It is widely used for multiple purposes. To assess the genetic
diversity and genetic differentiation of the species, genic SSR markers were mined
from transcriptome data for subsequent analysis of the genetic diversity and population
structure of natural populations. A total of 10645 potential genic SSR loci were
identified in 80482 unigenes. The average frequency was one SSR per 5.12 kb, and
the dinucleotide unit was the most abundant motif. A total of 67 alleles were found,
with a mean of 6.091 alleles per locus and a mean polymorphism information content
of 0.390. Moreover, the species exhibited a relatively moderate level of genetic diversity
(He = 0.399), with the highest was found in population XY (He = 0.469). At the regional
level, the southwestern region displayed the highest genetic diversity (He = 0.435) and
the largest number of private alleles (n=5), which indicated that the Southwestern region
may be the diversity hot spot of L. formosana. The AMOVA results showed that variation
within populations (94.02%) was significantly higher than among populations (5.98%),
which was in agreement with the coefficient of genetic differentiation (Fst = 0.076).
According to the UPGMA analysis and principal coordinate analysis and confirmed by
the assignment test, 25 populations could be divided into three groups, and there were
different degrees of introgression among populations. No correlation was found between
genetic distance and geographic distance (P > 0.05). These results provided further
evidence that geographic isolation was not the primary factor leading to the moderate
genetic differentiation of L. formosana. As most of the genetic diversity of L. formosana
exists among individuals within a population, individual plant selection would be an
effective way to use natural variation in genetic improvement programs. This would be
helpful to not only protect the genetic resources but also attain effective management
and exploit genetic resources.