| Hippophae is a kinds of significant water and soil conservative plant. It shows great genetic differentiation at different levels, such as within populations, among populations, at subspecies and even species levels. As distribution center and the origin area of Hippophae, China contains rich resources of sea buckthorn. In the present study, random amplified polymorphic DNA (RAPD) marker by 15 primers was used to analyse genetic divergence and population genetic variation of three endemic taxa in China, H. rhamnoides ssp. sinensis, H. rhamnoides ssp. yunnanensis, H. rhamnoides ssp. wolongensis. The main results are as follows :107 bands in total were generated from 251 individuals of 14 populations of H. rhamnoides ssp. sinensis using 15 primers. At subspecies level, the percentage of polymorphic bands (PPB) was 89.72%. Nei's gene diversity (h) was 0.204 and Shannon index (1) was 0.325. The means of three indexes (PPB, I and h) were 55.81%, 0.168 and 0.259 at population level. As a woody, moderately long-lived, obligatedly outcrossing and wind-pollinated species, ssp. sinensis might be regarded as somewhat lower genetic diversity than other plants with the same breeding system. 18.7% of genetic variation was found among populations (Gst=\$.7), which showed most of the variation existed within populations. The result was a little lower than the mean value of outcrossing species. It, however, was in accord with characters of its breeding system. Mantel test between genetic distance and geographic distance of 14 populations showed that they have significant correlation(r = 0.335, t = 2.371 > t0.05, P = 0.010) at 0.05 level. But no correlation was found between genetic distance and geographic distance when the range of distribution was narrow. In large altitude gradient, correlation could be found between genetic distance and altitude at 0.05 level (r = 0.285, t = 2.343> t0.05, P = 0.011), but not in small gradient .As for subpopulations of 5 populations with different environments, ssp. sinensis appeared different genetic differentiation. The isolation by the separate distribution of individuals, and the environments made the limited gene flow, which caused the distinct among-subpopulation genetic variation of S9 and S13 (Gst was 0.240 and 0.487, respectively). The plain environments of subpopultions of S11 S17 and S20 were in favor of gene flow among subpopulations. So, frequent gene flow was attributed to the low genetic differentiation among subpopulations of the above three populations (Gst was 0.194, 0.161 and 0.188, respectively).From the 15 primers, 12 primers that were detected plain bands were selected for theanalysis of H. rhamnoides ssp. yunnanensis. Altogether 112 bands were generated from 113 individuals of 6 populations. The percentage of polymorphic bands (PPB) was 92.86%. Nei's gene diversity (h) was 0.255 and Shannon index (I) was 0.397 at subspecies level. As about 6 populations, the means of PPB was 46.28%, h was 0.139, 7 was 0.214. The above results showed that genetic diversity of ssp. yunnanensis was high. Gst indicated genetic variation among populations was remarkable (Gst = 0.459). AMOVA received similar result (47.02%). The Gst was close to the mean value of inbreeding species (0.510). Mantel test between genetic distance and geographic distance of 6 populations showed that the two distance had no correlation (r = 0.437, t = 1.454< t0.05, P = 0.104). There were no correlation between genetic distance and altitude also (r = -0.117, | t | = 0.514< to.os, P = 0.324).12 primers that can received abundant polymorphic bands from all the 15 primer were used to analyse genetic diversity of H. rhamnoides ssp. wolongensis. All of 82 bands from 28 individuals of 2 populations were received. The percentage of polymorphic bands (PPB) was 78.05%. Nei's gene diversity (h) was 0.255 and Shannon index (I) was 0.384 at subspecies level. The means of three indexes (PPB, I and h) were 63.42%, 0.219 and 0.329 for populations, respectively. Most of genetic variation was within populations,... |
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