title: Genetic variation in cultivated Rheum tanguticum populations.
abstract: To examine whether cultivation reduced genetic variation in the important Chinese medicinal plant Rheum tanguticum, the levels and distribution of genetic variation were investigated using ISSR markers. Fifty-eight R. tanguticum individuals from five cultivated populations were studied. Thirteen primers were used and a total of 320 DNA bands were scored. High levels of genetic diversity were detected in cultivated R. tanguticum (PPB = 82.19, H = 0.2498, HB = 0.3231, I = 0.3812) and could be explained by the outcrossing system, as well as long-lived and human-mediated seed exchanges. Analysis of molecular variance (AMOVA) showed that more genetic variation was found within populations (76.1%) than among them (23.9%). This was supported by the coefficient of gene differentiation (Gst = 0.2742) and Bayesian analysis (θ B = 0.1963). The Mantel test revealed no significant correlation between genetic and geographic distances among populations (r = 0.1176, p = 0.3686). UPGMA showed that the five cultivated populations were separated into three clusters, which was in good accordance with the results provided by the Bayesian software STRUCTURE (K = 3). A short domestication history and no artificial selection may be an effective way of maintaining and conserving the gene pools of wild R. tanguticum.
authors.affiliation: Northwest Institute of Plateau Biology , the Chinese Academy of Sciences , Xining , China .
authors.forename: Yanping
authors.initials: Y
authors.lastname: Hu
authors.affiliation: School of Pharmacy , Henan University of Traditional Chinese Medicine , Zhengzhou , China .
authors.forename: Xiaolong
authors.initials: X
authors.lastname: Xie
authors.affiliation: Northwest Institute of Plateau Biology , the Chinese Academy of Sciences , Xining , China .
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: Northwest Institute of Plateau Biology , the Chinese Academy of Sciences , Xining , China .
authors.forename: Huaigang
authors.initials: H
authors.lastname: Zhang
authors.affiliation: Northwest Institute of Plateau Biology , the Chinese Academy of Sciences , Xining , China .
authors.forename: Jian
authors.initials: J
authors.lastname: Yang
authors.affiliation: Northwest Institute of Plateau Biology , the Chinese Academy of Sciences , Xining , China .
authors.forename: Yi
authors.initials: Y
authors.lastname: Li
keywords: ISSR; Polygonaceae; Rheum tanguticum Maxim. ex Balf; cultivated populations; genetic variation