Genetic diversity and population structure of sour jujube, Ziziphus acidojujuba

Sour jujube or wild jujube (Ziziphus acidojujuba), considered as the ancestor of cultivated jujube, is an economically and ecologically important species. However, little is known about the population genetics of this species across China. In this study, we detected genetic variation among 874 individuals from 31 natural populations covering the most representative distribution sites of sour jujube in China using nine simple sequence repeat markers. By Bayesian, phylogenetic, and principal component analyses, two genetic groups of sour jujube in China were identified. One group was almost from east of the Taihang Mountains in the North China Plain, and the other was from west of the Taihang Mountains in the Loess Plateau. The high levels of genetic diversity (H-E=0.659 and H-S=0.674) was detected in these populations, and the moderate differentiation was found among populations (F-ST=0.091, R-ST=0.068, G(ST)'=0.271). Populations from the North China Plain harbored higher genetic diversity (H-E=0.686 and H-S=0.706) than those from the Loess Plateau (H-E=0.646 and H-S=0.659) (P<0.05). Analysis of molecular variance revealed that within-population genetic variation (88 %) was higher than that among populations (12 %). High gene flow (Nm=6.572) and weak correlation between genetic and geographical distances (r(2)=0.026, P>0.05) suggested that gene flow occurred frequently among the populations. Understanding the genetic diversity and population structure could benefit germplasm conservation, genetic improvement, and systematic utilization of Ziziphus.