| Hybridization was ascribed to the incomplete reproductive isolation mechanism in Glycyrrhiza L.,which leads to interspecific introgression,and has an important influence on the population genetic structure.In this study,the applicability of SCoT markers was investigated by contrast analysis of SCoT and EST-SSR markers in the genetic diversity of Glycyrrhiza.Second,SCoT markers were used to assess the genetic diversity and population genetic structure in 16 wild populations of 5 species and 1 variation of Glycyrrhiza.,a total of 195 individuals,and explored the current situation of intraspecific genetic differentiation.Finally,we analysed the genetic structure and introgression mode of 4 sympatric groups,and discussing hybrid introgression effects on speciation and differentiation of species,and illustrated the formation and evolution trend of Glycyrrhiza.eurycarpa P.C.Li..The results show:1.A total of 358 bands were detected using 20 primers,among which 357 were polymorphic bands.The average percentage of polymorphic bands was 99.75%,and there was no significant difference in the average effective number of alleles(Ne)and the expected heterozygosity(He)between EST-SSR and SCoT markers.SCoT marker(E=17.333,Ai=21.145)was greater than EST-SSR(E=6.909,Ai=8.719)in assay efficiency.The systematic diagram of genetic relationship indicated that SCo T and EST-SSR markers grouped the 14 individuals into 3 major groups of the same.This cluster was in accord with the classical taxonomy,indicating that the 2 methods were both efficient in revealing interspecific or intraspecific genetic difference and relationship.These results indicate that SCoT markers bring a rich polymorphism and informativeness,and suitable for research on phylogenetic relationship,genetic diversity,genetic structure,and gene introgression of Glycyrrhiza species.2.Glycyrrhiza species are rich in genetic diversity,but there is a big difference between species,G.glabra L.has the highest level of genetic diversity(He=0.245,I=0.391),G.uralensis L.(He=0.238,I=0.384),G.eurycarpa P.C.Li.(He=0.237,I=0.383),the least is G.inflata Bat.(He=0.229,I=0.367).According to Nei's genetic differentiation coefficient and AMOVA variance analysis,it was found that there were significant differences(Gst,0.438 ~ 0.450)among 4 species of Glycyrrhiza,and the genetic variation was found mainly within populations(65% ~ 75%).Gene flow among populations(Nm = 0.625 <1),indicating that there may be a limited gene flow among different populations.Intraspecific population level and individual level of clustering and Mantel test showed a regional characteristic of resources distribution in Glycyrrhiza plant.The geographical and environmental conditions such as the abundant light and heat resources and arid in the southern and eastern Xinjiang is likely to promote the differentiation and migration of Glycyrrhiza species.And several Glycyrrhiza species meet each other in the south and eastern of the Tianshan Mountains region during the migration,offer the possibility to form a hybrid zone.3.Sympatric distribution is also affecting the genetic diversity within populations.The level of diversity within the sympatric groups is higher than the species level.Gene flow among species(Nm = 3.369)was greater than that of the intraspecific population(Nm = 0.642),indicating that there was an obvious gene exchange between species.Population structure analysis: the domain complex of the groups A,B,D is divided into two subgroups,C is divided into 4 subgroups,but different from species of division based on the morphological identification.A showed a bidirectional hybridization between G.uralensis and G.inflata introgression,and introgression tend to G.uralensis.B's 2 subgroups showed a regional environment-related,there may be genetic assimilation among species and with a certain degree of interspecific introgression.C: 2~4 subgroups introgress each other,resulting in the complex genetic background of each species,and G.uralensis differentiate into 3 subgroups,with different genetic structure.G.inflata is the formation of 2-4 subgroups.Some G.eurycarpa P.C.Li.With homozygous genetic background,divide into new subgroup.D: bidirectional gene gradually introgression between G.inflata and G.uralensis,introgression prefer to G.inflata.4.The origins and development tendency of G.eurycarpa P.C.Li.: Sympatric populations structural analysis pointed G.eurycarpa are products of sympatric species hybridization and gene introgression,different groups in different genetic composition: The one is involved in sympatric populations by way of backcross introgression events,because it has a certain tendency backcross(dominant species),resulting in G.eurycarpa type differentiation.Second,introgression by hybridization complex multiple species,produce new genetic type.In addition,the diversity level of G.eurycarpa is higher than that of other Glycyrrhiza species in the same region,and G.eurycarpa has a certain advantages in quantity and adaptability,which promotes the interspecific gene exchange of Glycyrrhiza plants.It is speculated that G.eurycarpa is the product of Glycyrrhiza species continue to divide,and accompanied by some gene flow and introgression process,gradually generated,is the formation of the parapatry and sympatry model of the product.In the process of continuous introgress with the sympatric species,the loss of hybridization type may be caused by backcrossing,it may also gradually be stably inherited type,making hybrids independent into ‘species' possible. |
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