SNP discovery in Cryptomeria japonica var. sinensis using restriction-site associated DNA sequencing (RAD-seq)

<p>Our study is the first to explore the genetic composition of ancient <i>Cryptomeria</i> trees across distribution range in China. <i>Background and Objectives:</i> <i>Cryptomeria japonica </i>var. <i>sinensis</i> is a native forest species of China; it is widely planted in the south of the country to create forests and for wood production. Unlike <i>Cryptomeria</i> in Japan, genetic Chinese<i> Cryptomeria </i>has seldom been studied, although there is ample evidence of its great ecological and economic value. <i>Materials and Methods:</i> Because of overcutting, natural populations are rare in the wild. In this study, we investigated seven ancient tree populations to explore the genetic composition of Chinese <i>Cryptomeria</i> through ddRAD-seq technology. <i>Results:</i> The results reveal lower genetic variation but higher genetic differentiation (<i>Ho</i>=0.143, <i>F_ST</i>=0.1204) than Japanese <i>Cryptomeria </i>(<i>Ho</i>=0.245, <i>F_ST</i>=0.0455). The 86% within-population variation is based on analysis of molecular variance (AMOVA). Significant excess heterozygosity was detected in three populations and some outlier loci were found; these were considered to be the consequence of selection or chance. STRUCTURE analysis and dendrogram construction divided the seven ancient tree populations into four groups corresponding to the geographical provinces in which the populations are located, but there was no obvious correlation between genetic distance and geographic distance. Demographic history analysis conducted by a Stairway Plot showed that the effective population size of Chinese <i>Cryptomeria</i> had experienced a continuing decline from the mid-Pleistocene to the present. Our findings suggest that strong genetic drift caused by climate fluctuation and intense anthropogenic disturbance together contributed to the current low diversity and structure. Considering the species' unfavorable conservation status, strategies are urgently required to preserve the remaining genetic resources.</p>