Classification And Genetic Diversitiy Of Medicinal Plants Polygala Tenuifolia Willd.and P.Sibirica Linn

Polygala tenuifolia Willd. and P. sibirica Linn. are two perennial Polygala L. herbaceous plants in the Polygalaceae family. Both plants have medicinal uses; notably, either plant can serve as the basis of Radix Polygalae, a medication in "Chinese Pharmacopoeia". The medicinal portions of these plants are their dried roots, and the main medicinal ingredient in these roots is tenuigenin. These two species have rather similar morphologies, and both species have large morphological variations; as a result, there are many intermediate types of these plants that are difficult to identify. Furthermore, both species are widely distributed across China and have large areas of overlapping distribution, increasing the difficulty of distinguishing between these two species, particularly for ordinary individuals. Thus, Radix Polygalae is frequently a mixture of P. tenuifolia and P. sibirica.Although both of these species can be used in Chinese medicine, certain studies have indicated that P. tenuifolia has better medicinal effects than P. sibirica. In this study, to discriminate between these two species, a principal component analysis of morphology, an assessment of root anatomy and molecular analysis using ISSR (inter-simple sequence repeat) markers were performed. Convenient morphological characters and ISSR indicators for distinguishing between the two species were found, and the genetic diversity and genetic structure of P. tenuifolia and P. sibirica were analyzed. The following results were obtained.(1) A total of12morphological characters were used to assess212P. tenuifolia specimens and229P. sibirica specimens by principal component analysis. From this analysis,4principal components accounting for71.355%of the variability were obtained. The main sources of morphological variation in the two examined species were leaf width, LL/LW, plant height, inner sepal length, inner sepal width, outer sepal length and carina length. Discriminant analysis indicated that the discrimination accuracies for P. tenuifolia and P. sibirica were91.5%and83.0%, respectively, and that the overall discrimination accuracy was87.1%.(2) Root transection was performed to investigate the root structures of P. tenuifolia and P. sibirica. The root structures of these species were extremely similar, although one major difference was the presence of a higher proportion of secondary phloem (which contains tenuigenin) in P. tenuifolia than in P. sibirica; this difference may explain why P. tenuifolia has a stronger medicinal effect than P. sibirica.(3) In our molecular study,20ISSR markers were selected, and372loci were obtained. Both P. tenuifolia and P. sibirica exhibited high genetic diversity at the species level. A low level of genetic differentiation and a high level of gene flow among populations were detected for P. tenuifolia. A high level of genetic differentiation and a low level of gene flow among populations were detected for P. sibirica.(4) AUPGMA clustering analysis based on ISSR examination indicated that all P. tenuifolia germplasms were in one group and that all P. sibirica germplasms were in another group. Thus, the two species could be easily and accurately distinguished using the20ISSR markers selected in this study.The above experiments and analyses clearly demonstrate that P. tenuifolia and P. sibirica are two distinct species. These species can be identified by morphology and root anatomy, and ISSR markers are a stable indicator that can readily be used to distinguish between these two species.