Abstract
As a precious and rare genetic resource, ancient Platycladus orientalis L. (Cupressaceae) has important scientific, cultural and historical value. The ancient temples and royal cemeteries in the middle reaches of the Yellow River contain the most concentrated and abundant distributions of ancient P. orientalis. Due to unfavorable conditions, the genetic resources of ancient trees are facing great threats and challenges; thus, it is urgent to strengthen the evaluation of the genetic resources of ancient P. orientalis. In this study, we used nine polymorphic nuclear simple sequence repeats (nSSRs) to evaluate the genetic resources of 221 individuals in 19 ancient P. orientalis populations in the middle reaches of the Yellow River. These selected polymorphic nSSR loci can be used reliably and rapidly in P. orientalis genetic studies. Our study showed that the 19 ancient P. orientalis populations have high genetic diversity (mean H = 0.562, He = 0.377). High historical gene flow (mean Nm = 1.179) and high genetic differentiation (mean Fst = 0.184) were observed in the ancient P. orientalis population. The analysis of molecular variance (AMOVA) showed that higher genetic variation existed within populations (93%) rather than among populations (7%). The genetic structures showed that the 19 populations were divided into two groups. The Mantel test and neighbor-joining (NJ) tree analysis showed no geographical distribution characteristics among populations, which may indicate a history of transplanting by ancient humans. Our research provides a theoretical basis for the protection and utilization of ancient P. orientalis germplasm resources and exploration of the historical origin and genetic relationships among the populations of P. orientalis on a large scale in the future.
Highlights
Platycladus orientalis L. (Cupressaceae), which belongs to the family Cupressaceae, is a monoecious, evergreen conifer that originates in China and is distributed as far away as Japan, North Korea and Europe [1]
We found that the distribution area of the ancient P. orientalis populations in the middle reaches of the Yellow River was fragmented in our field investigations and that the geographical distance among populations has far exceeded the distance over which pollen could spread effectively (100 km) [67]
19 ancient P. orientalis populations were divided into two groups in the STRUCTURE analysis
Summary
Platycladus orientalis L. (Cupressaceae), which belongs to the family Cupressaceae, is a monoecious, evergreen conifer that originates in China and is distributed as far away as Japan, North Korea and Europe [1]. (Cupressaceae), which belongs to the family Cupressaceae, is a monoecious, evergreen conifer that originates in China and is distributed as far away as Japan, North Korea and Europe [1]. The presence of P. orientalis has been historically demonstrated by records of ‘The Book of Songs’, which was the first anthology of Chinese poetry written approximately 3000 years ago [2]. Ancient coffins excavated in various parts of China have provided archaeological evidence proving that the extensive cultivation of P. orientalis has a history spanning thousands of years [3]. Greening Committee and the National Forestry Administration in 2005, ancient P. orientalis are mainly located at temples, historical sites and cemeteries in the vicinity of the middle reaches of the Yellow River. The middle reaches of the Yellow River are considered one of the most important birthplaces of Chinese civilization.
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