Study On The Genetic Diversity And Distribution Structure Of Polygonatum Cyrtonema In Anhui Province

Polygonatum cyrtonema,a perennial rhizomatic herb of Polygonatum in Asparagaceae,is endemic to China and mainly distributed in the Yangtze River.It is one of the three major source plants of the Chinese medicinal material“huangjing”,with the developed rhizome as medical and edible parts.The underground rhizomes of P.cyrtonema have medicinal properties in replenishing spleen,moistening lungs,increasing immunity,and so are commonly regarded as drug homologous food.It has small white flowers,overhanging,large leaves,hoar frost under the leaves,prominent veins,and has good ornamental value.In recent years,the research on P.cyrtonema is mainly focused on systematic classification,drug composition activity and cultivation,while the population genetics research is relatively limited.The hilly mountains in western and southern Anhui province are one of its main natural distribution and artificial cultivation areas.However,the number and size of the wild population were gradually reduced due to human interference and environmental changes.We assessed the genetic diversity and structure of P.cyrtonema germplasm resources in Anhui by the developed microsatellite primers and analyzed morphological variation preliminarily.We chosed the sibling species P.filipes and P.odoratum as outgroup,for the purpose of providing guidance for the protection and artificial cultivation of P.cyrtonema germplasm resources.The main research results are as follows:?1?The test materials were sampled from 17 natural populations in Anhui province,covering the main distribution areas of P.cyrtonema in Anhui.Among them,there are 13populations of P.cyrtonema,with a total of 312 individuals;2 populations of P.filipes,total 46 individuals;2 populations of P.odoratum,23 individuals in total.P.filipes and P.odoratum were both collected as outgroup.?2?Nine pairs of SSR primers with good polymorphism and stability were selected from the published microsatellite primers,and 231 alleles were detected in 17 natural populations by PCR amplification and population typing.The average genetic diversity of the sampled three species was moderate,and the number of alleles?NA?was 7.634,the number of effective alleles?NE?was 4.399,the observed heterozygosity?HO?was 0.567,the expected heterozygosity?HE?was 0.644.Averaged across P.cyrtonema in Anhui province,the number of alleles?NA?was 7.983,the number of effective alleles?NE?was4.527,the observed heterozygosity?HO?was 0.539,the expected heterozygosity?HE?was0.645.The genetic diversity indexes of P.filipes?N_A=8.389,N_E=4.743,H_O=0.602,H_E=0.664?and P.odoratum?N_A=4.611,N_E=3.227,H_O=0.716,H_E=0.616?were both close to the corresponding level of P.cyrtonema,with no significant difference.?3?The consensus neighbour-joining tree and Splits tree,combined with STRUCTURE and PCoA analysis results showed that the 17 studied populations on whole level were clustered into five groups.The 13 populations of P.cyrtonema were clustered into three groups with high support.Among them,there are six populations?MC,FLS,BJS,HHGD,JHGS,JHHS?in Xuancheng and Chizhou City as group I,four populations?YLC,HG,HGGS,HT?in Huangshan City as group II,and three populations?TTZ,YLP,TZS?from Dabie Mountains area as group III.The two populations of P.filipes?flsC,hgC?and P.odoratum?ttzY,jhs Y?respectively,each clustered into their own group?group IV and V?.The three genetic groups of P.cyrtonema are closely related to mountain ranges.The group I is distributed in the Tianmu Mountains?including Jiuhua Mountain?,the group II is distributed in the Huangshan Mountains,and the group III is distributed in the Dabie Mountains.The mean genetic diversity of the three genetic groups was,respectively,group I?N_A=8.167,N_E=4.469,H_O=0.599,H_E=0.682?,group II?N_A=7.139,N_E=4.048,H_O=0.488,H_E=0.597?and group III?N_A=8.741,N_E=5.281,H_O=0.487,H_E=0.637?.There is no significant difference between them.?4?According to the AMOVA,on the overall level of 17 populations,84.0%of the total genetic variance was found within populations,which was much higher than that between the populations?15.96%?.Among the 13 P.cyrtonema populations,the variation was mainly from within the population?85.22%?,which was significantly different from the variation between the populations?14.78%?,which might be relevant to this species'reproduction and biological characters.The genetic differentiation was evident among the populations of P.cyrtonema,and the average genetic differentiation coefficient(F_ST)of the 17 sampled populations was 0.118,the FST of P.cyrtonema populations among different groups was 0.144,which was significantly higher than that between populations within groups?0.065?but lower than that between populations of different species?0.185?.The frequency distribution simulation of F_STT map among groups P.cyrtonema overlapped0.584 with that among species and significantly greater than that within groups 0.217.Morphological studies?leaf length,leaf width,fruit stem length and leaf length:width ratio?also exhibited that there were obvious morphological differences in the three branches of P.cyrtonema,so P.cyrtonema may have differentiated into three different species or cryptic species in Anhui province.?5?No spatial genetic structure described by the IBD?isolation-by-distance?model was detected in 17 total population groups?r=?0.014,P=0.872?or 13 P.cyrtonema populations?r=0.148,P=0.196?by Mantel Test.The results of gene flow analysis revealed that the historical gene flow level of each population was small,but the gene flow level within the group was significantly stronger than between groups,and the gene flow level between groups was significantly stronger than between species.There were significant differences among them?F=29.331,P<0.001?,which might infer that there may have been significant segregation in the history of each population.Contemporary gene flow increasesed,the geographical distance between populations is small,and there was no significant difference in gene flow within groups,between groups,and between species?F=1.748,P>0.05?.The increasesed gene flow may be one of the reasons for the poor morphological differentiation among populations.?6?Based on the above research results,the following protection suggestions were put forward for P.cyrtonema in Anhui province:the three genetic groups of P.cyrtonema should be considered as independent units for conservation and breeding management in the Anhui region.In order to provide more efficient support for the cultivation and breeding of the germplasm resources of P.cyrtonema in Anhui province,it is necessary to further study whether there are differences in the specific distribution range and the effective components of the three genetic groups of P.cyrtonema in Anhui province.