| Orchid and pollinating insects have perfect coevolution relationship, it’s considered to be the most evolved taxa in monocotyledon, and mostly are endangered plants. In China, all orchids belong to second focused protection wild plant of country. Jiangxi Province is surrounded by mountains, with diverse ecological environment and rich mineral resources. Cymbidium faberi Rolfe population is abundant, but with habitat destruction, over-excavation and other reasons, it faces population reduced, the distribution region atrophy and other issues. ITS and cpDNA are important molecular markers for studying many angiosperm taxa systems evolution and biogeography.We investigated distribution resources of wild C. faberi Rolfe in Jiangxi Province, collected255individuals of16populations from Mufu Mountain, Jiuling Mountain, Luoxiao Mountain, Wuyi Mountain, Huaiyu Mountain in Jiangxi Province and1SW population from Wuyi Mountain. And by using ITS and cpDNA molecular markers to analyze the genetic diversity of Cymbidium faberi Rolfe population, to assess C. faberi Rolfe population genetic diversity level, genetic structure and genetic differentiation among populations. And as a theoretical basis for appropriate protective measures, the results provide reference for source protection and rational development utilization of C. faberi Rolfe. The results were as follows:(1) The ITS region length ranged from654bp to659bp, G+C content ranged from54.17%to68.55%. ITS1region length ranged from240to242bp,5.8S region length was conserved of163bp, ITS2region length ranged from250to255bp. ITS1,5.8S, ITS2region G+C content were54.96%～70.54%,46.63%～60.74%,58.27%～71.31%. ITS sequence had178mutation sites,126parsimony informative sites.11ITS types existed in17C. faberi Rolfe populations of Jiangxi province,9populations had variation. There was single ITS type in Mufu Mountain,3ITS types in Huaiyu Mountain and Jiuling Mountain,5and6ITS types in Luoxiaos Mountain and Wuyi Mountain. ITS sequence AMOVA analysis revealed genetic variation among population was18.22%, genetic variation within population was67.87%, the differences within population and among populations were highly significant. FST=0.32127, high genetic differentiation within populations. Nm=1.0563>1, which mean that the number of immigration was large, gene flow was high.(2) The length of the petB-petD intergenic sapcer in C. faberi Rolfe chloroplast DNA ranged from498bp to508bp, G+C content was32.8%.10variable sites were detected, including the missing of two fragments and base mutation of the eight sites, of which there are six informative sites.11haplotypes existed in17C. faberi Rolfe populations of Jiangxi province,9populations had intraspecific variation. There were2haplotypes in Mufu Mountain, Huaiyu Mountain and Jiuling Mountain,5haplotypes in Luoxiaos Mountain and Wuyi Mountain. Take chloroplast haplotype diversity as consideration, genetic diversity in9populations was0, the maximum haplotype diversity was GX population (h=0.7091), the minimum was SW population (h=0.1538). Take nucleotide diversity as consideration, genetic diversity in9populations was0, the maximum nucleotide diversity was CY population (p=11.947×10-3), the minimum was JA population (p=0.651×10-3). The average genetic diversity among17populations Ht(se) was0.324(0.1094), the average genetic diversity within17populations Hs (se) was0.213(0.0682), genetic differentiation coefficient Nst (se) was0.543(0.1883) and Gst (se) was0.342(0.0547). U test was used for the geographical structure analysis of C. faberi Rolfe, Nst> Gst, UNst/Gst=1.03<U0.05=1.96, P>0.05, the populations were lack of apparent phylogeographical structure. cpDNA AMOVA analysis showed that genetic variation among populations was50.03%, genetic variation within populations was48.08%, the differences within populations and among populations were highly significant. FST=0.51518, high genetic differentiation within populations.(3) Combined ITS with petB-petD intergenic spacer region of cpDNA, there was a high level of genetic diversity in Luoxiao Mountain and Wuyi Mountain. Widely distributed ITS type did not exist in CY population from Luoxiao Mountain. C. faberi Rolfe individuals of GX population from Wuyi Mountain with both analysis methods did not contain widespread ITS type and haplotype and contained a variety of haplotypes within population.(4) ITS fragment and chloroplast DNA fragment of petB-petD mismatch distribution analysis (Mismatch distribution analysis), have shown that observed curve consistent with the expected expansion curve in the mismatch distribution curve, and P value of SSD, HRag was larger than0.05, indicated differences was significant and expansion was detected in C. faberi Rolfe populations.(5) Neutrality test for evolutionary model was used for ITS fragment and chloroplast DNA petB-petD fragment on the species and population level. ITS neutrality test Tajima’s D was-1.66078, P=0.01<0.05, the result was significantly negative, showed that populations reject neutral evolution hypothesis, and C. faberi Rolfe may have experienced expansion events. Chloroplast DNA neutrality test Tajima’s D was-1.32051, P=0.076>0.05, the results were not significant.(6) IBD analysis of genetic distance and geographical distance of17C. faberi Rolfe populations, showed that the geographical distribution was not related to genetic distance.(7) We surveyed C. faberi Rolfe populations resources, combined with C. faberi Rolfe genetic diversity and genetic differentiation level, proposed reasonable protection strategies, such as WGS, HF, JGS, SW population with high level of genetic diversity and rich germplasm resource for situ conservation; CY and GX population that genetic differentiation was significant and individuals was rare for ex-situ conservation; use rapid breeding technologies to expand the number of population and distribution; protect pollinators that were pollinating insects. |
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