| Natural hybridization plays an important role in the formation and differentiation of species.Because of the imperfect reproductive isolation mechanism between the species of Glycyrrhiza L.,the hybrids between the neighboring and the sympatric distribution species often lead to introgression of the genes,have an important impact on the genetic structure and species differentiation of natural populations.In this study,based on 35,717 genes sequence data of the transcriptome in Glycyrrhiza inflata,the SSR was mined and analyzed.The genetic diversity and species composition(parent and offspring)of the hybrid populations in different hybrid regions were selected by the selected transcriptome SSR.The structure,gene introgression degree and direction were studied.On this basis,the correlation analysis of soil water content,salt content,species composition and genetic diversity in different hybrid areas was carried out.The differences in hybrid species composition and gene introgression in different hybridization areas were revealed,and the effects of natural hybridization on the formation and genetic differentiation of Glycyrrhiza under different environmental selection pressures were investigated,so as to provide a basis for the systematic classification research of Glycyrrhiza and the study on the mechanism of speciation and adaptive evolution of hybrid species.These significant results were summarized as follows:1.In this study,a total of 7,660 transcriptome sequences containing 10,378 SSR loci were shown by transcripting SSR results of G.inflata Bat.Among the searched transcriptome SSRs Glycyrrhiza inflata,the frequency of tri-nucleotide repeats(5,111,47.60%)is approximated to that of di-nucleotides repeats(5,102,47.51%),indicating that these two repeat types are the most dominant for G.inflata Bat.The the most abundant tri-nucleotide motifs CAA/GAA/AAC;followed by the most abundant SSR motifs CT/TC of di-nucleotide repeat was.The 41 pairs of primers screened with high polymorphism.The polymorphism information ranged from 0.173 to 0.644,and the primer polymorphism amplification rate was 83.7%.It is a new SSR marker for studying the genetic diversity of the natural population of Glycyrrhiza L..2.The genetic structure and hybrid composition analysis of different hybridization areas showed that the hybridization type of the Glycyrrhiza hybrid area and its introgression direction and extent were related to the species type and habitat difference of the distribution area:(1)Alar B and Turpan hybrid areas are interspecific hybrids of G.glabra and G.inflata and introgressed species of hybrid backcross and parental backcross.Among them,there are two hybrid types in the Alar B hybrid region,which are two-way hybrid introgression of hybrid progeny and two parental species,and the hybrid region is composed of F2 generation and backcross introgression;the Turpan hybridization zone is mainly composed of F1 generation is the main,followed by the backcross generation with the licorice,which may be related to its relatively closed undisturbed gully habitat.(2)The Korla?Yanqi and Gansu distribution areas are interspecific hybrids of the G.inflata Bat.and G.uralensis,and introgressed species formed by backcrossing of hybrid progeny and parents.Among them,the composition of Korla hybridization area is mainly F2 between of G.inflata Bat.and G.uralensis;the Yanqi hybrid area is mainly F2,and the infiltration of the hybrid progeny and G.uralensis is unidirectionally infiltrated,and the degree of infiltration is different,filtration,and the degree of infiltration is different,which leads to the morphological differentiation of G.inflata Bat.and G.uralensis;the Gansu hybrid area is the F1 generation of interspecific hybridization between G.inflata Bat.and G.uralensis and its one-way backcrossing with Glycyrrhiza uralensis.3.The population genetic diversity of G.inflate,G.glabra,G.uralensis and hybrid types was quite different(H=0.545?0.5523?0.561?0.667;I=1.034?1.048?1.052?1.295),hybrid group>> G.uralensis > G.glabra > G.inflata Bat..Genetic diversity has a certain relationship with soil water content and salt content in different distribution areas of the same species.The lower the soil water content in the G.inflata growing area,the lower the genetic diversity,and the selection pressure of the arid environment makes the genotype with strong drought tolerance of G.inflata adapt to the extreme environment;the higher the soil water content,the other parent species emergence of hybridization and introgression has the potential to promote genetic diversity.The lower the soil water content of the G.glabra,the lower the genetic diversity,the selection pressure of the arid environment makes the genotype with strong drought tolerance of G.inflata adapt to the extreme environment;the higher the water content,the emergence of the species of another parent,the type of hybridization and introgression are formed,resulting in higher genetic diversity.The higher the soil water content of G.glabra L.,the lower the genetic diversity,the lower the selection pressure of the arid environment(increased water content),and the more similar the genotypes of G.glabra.In addition,the higher the soil salinity of the hybridized area,the higher the genetic diversity of the hybrid type,and the selection pressure of the high salt environment makes the genotype of the hybrid type more complicated.The above results indicate that the species distribution of Glycyrrhiza has a certain relationship with soil water content and total salt content,and there is consistency between soil factors and genetic diversity trends.Environmental selection pressure may play a role in the formation and differentiation of licorice hybrid species. |
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