In this study, a genetic diversity analysis was performed using SCoT markers to assess phylogenetic relationships among 278 Prunus sibirica individuals from 10 different populations in Inner Mongolia. Twenty-three SCoT primers were used for the amplification of genomic DNA from Prunus sibirica. A total of 292 clear bands were obtained, 289 of which were polymorphic. The average number of amplified bands per primer was 12.7, with a polymorphism percentage of 98.87%. In a previous study, researchers used SRAP (Ai et al. 2011), AFLP (Wang 2008), RAPD (Lu 2008), and ISSR (Liu et al. 2011; Duan et al. 2010; Li et al. 2009; Liu et al. 2007) molecular markers to analyze the genetic diversity of Prunus sibirica in different regions, and the results showed that the polymorphism ranged from 58–90%. In contrast, the SCoT molecular markers were found to be more polymorphic than other molecular markers. Therefore, SCoT markers may be suitable for the study of genetic diversity according to molecular markers in Prunus sibirica. A previous study of the genetic diversity of Prunus armeniaca (Li 2014) indicated H, I, and polymorphism percentage values of H = 0.1720, I = 0.2576 and PPB = 50.07%; Sibirica (Ma 2014) indicated H, I, and polymorphism percentage values of H = 0.2318, I = 0.3530 and PPB = 76.74%. However, the H, I, and polymorphism percentage values obtained in the present study were H = 0.2571, I = 0.3989 and PPB = 97.94%, respectively. We showed that the genetic diversity of the Prunus sibirica populations in Inner Mongolia is higher than that of Prunus armeniaca and Sibirica. This result was consistent with the conclusions of other scholars that the genetic diversity of outbred species is higher (Hamrick 1989; Zheng et al. 2008).
As a perennial wild resource, Prunus sibirica is widely distributed in Inner Mongolia and exhibits a large distribution area, long-term evolution and considerable diffusion as well as ecological diversity, leading to rich genetic diversity. According to Wright (1972), when the FST (GST, genetic differentiation coefficient) value is 0 to 0.05, the genetic differentiation within populations is low; when the FST value is 0.05 to 0.15, the genetic differentiation within populations is moderate; when the FST value is 0.15 to 0.25, the genetic differentiation within populations is high; and when the FST value is greater than 0.25, the genetic differentiation within populations is great. In our research, the GST was 0.3601. The results showed that the genetic differentiation coefficient of Prunus sibirica within populations in Inner Mongolia was relatively high, with among-population genetic differentiation of 39% and a within-population genetic differentiation of 61%. Wang (2019), Liu et al. (2012) and Ma (2013), who used SSR and ISSR markers for Prunus sibirica and wild apricot genetic diversity analyses, showed that within-population variation dominated, and the among-population variation was much lower than the within-population variation. which is similar to the results of a previous study in Prunus sibirica.
The reasons for the high within-population genetic differentiation of Prunus sibirica in Inner Mongolia may include the following: 1. Gene flow is an important factor affecting genetic differentiation in a population when Nm < 1, which can conversely effectively prevent genetic differentiation caused by genetic drift. The Nm value for Prunus sibirica in Inner Mongolia was 0.8884, indicating that genetic drift was not the main factor influencing the genetic differentiation of the Prunus sibirica populations in Inner Mongolia. Some gene flow exists among the Prunus sibirica population in Inner Mongolia, but the Nm intensity was relatively low. 2. The self-incompatibility breeding characteristic of Prunus sibirica may eliminate self-pollination as a possible cause of genetic differentiation, and its breeding mainly relies on natural pollination or pollination by visiting insects such as bees, flies and a few butterflies (Liu et al. 2010; Liu 2010). Although pollen can be spread by insects and by wind over long distances, the large distribution area and discontinuities in the population distribution of Prunus sibirica are restricted due to geographic isolation or habitat fragmentation (Wu et al. 2015), thus weakening the gene flow within populations of Prunus sibirica. 3. Some populations have been destroyed or their habitats have been degraded, resulting in a gradual fragmentation of the population distribution and limiting the gene flow within the populations. Therefore, Prunus sibirica in Inner Mongolia shows high within-population genetic differentiation under the influence of multiple factors, such as physical geographic isolation and human activities.
In the present study, the genetic structure of Prunus sibirica populations in Inner Mongolia was analyzed. From the clustering diagram, principal component analysis, and structure analysis, we can see that most of the populations are clustered together with a similar geographic distribution, and the Mantel test showed a significant correlation between the genetic distance and geographic distance and between the genetic distance and altitude of the Prunus sibirica studied (r = 0.0426, P ≦ 0.4790;r = 0.0305, P ≦ 0.4260). Therefore, we hypothesized that a geographic isolation effect exists among populations of Prunus sibirica populations in Inner Mongolia, weakening the opportunities for gene flow within the populations and causing the intensification of genetic differentiation within populations. The clustering diagram, principal component analysis and structure analysis of the 278 individuals divided the populations into two groups ( I and II ). KSK, WJG, KYZ, and KZH were clustered in group I; LC, BLY, WLS, AL, and ZLT were clustered in group II; and only the 22 individuals in the ZLA group were divided between the two groups. A certain degree of gene flow exists among the subgroups, and gene flow also affects the population structure of Prunus sibirica (Liu et al 2012). This may occur because of the existence of many mountains and areas of sandy land in Inner Mongolia, and the topography and landforms are very complex. Thus, topographic barrier characteristics are prominent in the regional distribution, resulting in a natural isolation effect on different provenances of species and weakening the gene flow opportunities among populations. Second, habitat fragmentation is also an important factor that affects the composition and structure of the ecosystem and the genetic structure of a species.