| Codonopsis pilosula (Franch.) Nannf., a perennial herb of Campanulaceae, is an important medicinal plant in China which had been historically used as one type of authentic gingeng for thousands of years. Its wild resources have decreased remarkably due to long-time of over-collection; and instead, large-scale cultivation practice has been conducted for centuries. In this thesis, the current pattern of genetic diversity of wild and cultivated populations of this species was extensively surveyed. In addition, some possible impacts of over-harvesting on genetic diversity of wild populations and cultivating on that of cultivated populations were explored; strategies for in-situ and ex-situ protection and conservation of the genetic resources of this species were suggested. The purposes of this study were aimed to provide practical and effective schemes for protection, conservation and sustainable utilization of germplasm resources of medicinal plants.A total of 463 samples from eight wild and eight cultivated populations were collected from Shaanxi, Shanxi and Gansu provinces. In addition, 138 samples from 7 populations and another 150 individuals from 5 populations were separately collected in different times from Longxi county of Gansu province. Both inter-simple sequence repeat (ISSR) marker and randomly amplified polymorphic DNA (RAPD) marker were employed to estimate their genetic diversity, genetic structure and spatial distribution of the diversity. The research contents and conclusions were listed as follows:1. Both the wild and the cultivated populations of C. pilosula maintain a relatively high level of genetic diversity. The wild populations were found to have a relatively high genetic diversity with Pp = 96.18%, h = 0.288, and I = 0.442, and the major genetic variation was found within population (73.21%). The cultivated populations also displayed a relatively high level of genetic diversity (Pp = 96.18%, h = 0.266, I= 0.414), but more genetic variation existed within populations (82%). At species level, C. pilosula exhibited a relatively high genetic diversity with Pp = 97.0%, h = 0.285 and I = 0.440, and the major genetic variation resided within population (76.70%). The genetic diversity level and genetic structure of C. pilosula were consistent with the general patterns of wide-spread, perennial and outcrossing species.2. The genetic diversity of wild populations of "Lu Dangshen" from Changzhi county of Shanxi province is obviously decreased due to over-harvest in the history. The result showed that the genetic diversity of wild populations of "Lu Dangshen" from Changzhi was significantly lower than that of other wild populations concluded in this study. Its value (h =0.2090, I = 0.3272) was nearly equal to that of Adennophora lobophylla, an endangered species of the same family, and that of other endangered plants of relative families. The current genetic diversity pattern of wild populations in this area might be attributed to the severe over-harvesting practice recorded in the history. The over-harvest in the past had resulted in a severe decrease of the species individuals and population size. For this reason, a great genetic bottleneck was formed, and as a consequence, restrained the genetic diversity of this species.3. The present irregular and sparse cultivation practices of C. pilosula were proved to be an efficient way to maintain genetic diversity of this species. Although the genetic diversity of the cultivated populations was generally lower than that of wild populations, but the cultivated populations in Changzhi of Shanxi province showed much higher level than that of wild populations in the same area. This finding suggested that the current cultivation practices might be an efficient way to maintain the genetic diversity of C. pilosua. This primary conclusion was further supported by an investigation on the cultivated populations from Longxi county of Gansu province and a comparison with that of Changzhi populations. Document showed that the cultivation of C. pilosula was started from 1964 and the germplasm was introduced from Changzhi of Shanxi province. The current genetic diversity level of the cultivated populations from Longxi was found almost equal to that of the cultivated ones from Changzhi. Furthermore, different populations distributed at different height of altitude around Longxi county exhibited altitude-correlated variations of population genetic diversity. This tendency implied that, through 40 years of cultivation, populations of C. pilosula cultivated in this area might have generated new variations adaptive to micro-environment. All these results suggested that the present cultivation practices, i.e., random collecting, preserving, and planting seeds of C. pilosula, and the spatial isolation and heterogenous habitat of populations, might be the main reasons for the efficient conservation of genetic diversity of the studied species.4. An effective sampling strategy for conservation of C. pilosula should consider not only the population number and the population size, but also the sampling range of individuals and the spatial distribution of populations. Based on the above results, we proposed a practicable sampling strategy for in situ and ex situ germplasm conservation of C. pilosula as follows. First, the full germplasm collection program should be divided into several parts according to the administrative regions (provinces), and from each regions, at least four wild and three cultivated populations should be collected. Second, more detailed collection separately including at least four wild and three cultivated populations should be conducted within several germplasm distributing centers, in addition to the general collection for each province. For example, in the authentic distribution and cultivation region of "Lu Danshen" in Changzhi county of Shanxi province, and in Wenxian county of Gansu province where was mainly producing "Suhua Danshen", additional sampling should be carried out. Third, special attentions should be pay on different ecotypes, agrotypes and landraces in the process of germplasm collection, and the sampling schemes for these special types should be planed respectively according to their abundance and geographical distribution. Forth, the sample size for each population was 25-30 individuals, but the sampling range should be as wide as possible. Based on these basic principles of sampling strategy, more detailed implementary schemes for in situ and ex situ germplasm conservation of C. pilosula were proposed.This study explored comprehensively for the first time the common questions encountered in the resources development, germplasm conservation and sustainable utilization of medicinal plants by employing C. pilosula, a wild-spread species, as a research model. Our results showed that over-harvest of the wild resources would result in a severe genetic bottleneck and consequently decrease significantly the genetic diversity of wild populations. However, the present irregular and sparse cultivation practices, i.e., random collecting, preserving, and planting seeds without deliberate selection, might be an effective way to conserve genetic resources of medicinal plants. These findings are of significant theoretical and practical values for protection and conservation of genetic resources of medicinal plant as well as other species.
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