| Rhododendron rex L(?)vl.subsp.rex belongs to the family Ericaceae and subgenus Hymenanthes,which has high value in Landscape horticulture.The wild populations of R rex subsp.rex are mainly distributed in Yunnan Province and Sichuan Province in China.In recently years,the population has been severely damaged due to human disturbance,which caused the population is in a state of recession.IUCN has classified the plant as a vulnerable level.In order to explore the mechanism and main causes for its endangered mechanism,we designed experiments to study the relationship between seed germination traits and various ecological factors.Using microsatellite markers(SSRs)to learn the genetic diversity and structure of R.rex subsp.rex.Based on the results of the study,we analyzed the causes of the decline of populations of R.rex subsp.rex,and put forward the corresponding protection strategies and management measures.The main results are as follows:1.Seed Physiology of Rhododendron rex subsp.rex.The seed of Rhododendron rex L(?)vL subsp.rex hasn't obvious dormancy.The dark environment and high temperature inhibited its seed germination.Under the optimum temperature and light condition,the seeds has high germination rate.It is considered that the temperature condition at 20 ? or 15?25 ? is the optimum temperature condition for seed germination.Low concentration of GA3 had no significant effect on germination.However,1000ppm GA3 significantly inhibited seed germination.The germination of R rex subsp.rex showed a decreasing tendency with the increasing concentration of PEG-6000,and was significantly inhibited when concentration ?11.5%.The storage test showed that the seeds of R rex subsp.rex have good stamina to storage.The germination rate could keep high level after 9 months storage.Thus,we can conclude that the seed isn't recalcitrant seed.The Seed after storage germinates under illumination,the germination ability was mainly affected by the storage time and the interaction of storage time and the storage temperature.Under the dark condition,the germination ability was mainly affected by the storage temperature,the germination rate was very low after storage with 4?.2.Conservation genetics of Rhododendron rex subsp.rexBased on the 8 micro satellites(SSR)loci,we analyzed the genetic diversity and genetic structure of R.rex subsp.rex in Jiaozi Mountain,Yunnan Province.The genetic diversity of R rex subsp.rex has intermediate level in Rhododendron(PPB%=100%?NA=3.906?NE=2.422?H=0.532?I=0.966),and low genetic differentiation and high gene flow between the 4 altitude patches.Cluster analysis by UPGMA and Bayesian and PCoA showed that the four altitude patches and possibility subgroups could not be effectively distinguished.Hardy-Weinberg equilibrium(HWE)showed that four altitude patches conform to HWE test.The bottleneck effect test showed that the four altitude patches had no bottleneck effect in recent years.But in the history,the four altitude patches experienced bottleneck effect,and the number of groups had contracted.Based on the analysis of the seed physiology,genetic diversity and genetic structure of R.rex subsp.rex.Combined with the field investigation,it is considered that R.rex subsp.rex has intermediate genetic diversity level.Therefore,we suggest to strengthen the ex situ conservation,with the off site conservations for R.rex subsp.rex.In view of the situation that the seed of R.rex subsp.rex would have a low germination rate in the dark after storage with cold temperature,which is similar to the natural habitat of R.rex subsp.rex.We advise to moderately clear herb and shrub under R.rex subsp.rex in its main distribution region which has shaded effect,and moderately expand forest gap size in its main distribution region.In addition,artificial nursery establishment were also suggested to help the natural population to expansion and recovery. |
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