| Landscape fragmentation is the main factor that leads to the loss of biodiversity and species extinction,and it is also one of the important factors that threaten the survival of natural organisms.Generally,there are more green patches in cities,but it is not clear how the urban matrix affects plant genetic diversity.In order to explore the above problems,this study analyzed genetic diversity and genetic structure of wild populations of Setaira viridis based on SSR molecular markers.Twelve pairs of markers were screened out from 20 pairs of molecular markers of Setaira viridis.Forty-five populations from Changsha and surrounding areas were analyzed for genetic diversity and genetic structure of 209 samples of Setaira viridis.Through genetic pattern and landscape or environmental characteristics,the genetic diversity and genetic structure of Setaira viridis were analyzed.The correlation analysis of symptoms determined that there was no relationship between the spatial genetic structure of plant population and urban landscape,and whether landscape fragmentation had a significant impact on the genetic diversity of plant population.The results of this study can provide a basis for studying the relationship between plant genetic diversity and urban landscape through genetic diversity and genetic structure of wild Setaira viridis resources in Changsha and its surrounding areas,and also provide a reference and theoretical basis for urban planning based on theoretical data.The main results are as follows:(1)12 pairs of primers with more bands,strong signal and clear background were screened for SSR-PCR amplification,and the suitable annealing temperature of 12 pairs of primers was determined.(2)Twelve microsatellite loci showed that the number of effective alleles Ne w as 6.920,Shannon information index I was 2.075,observed heterozygosity Ho was 0.705,allele richness AR=7.27,inbreeding coefficient Fis was 0.152.AMOVA analysis showed that the percentage of variation among populatio ns was 17%,among populations and within populations was 12%and 71%.(3)Based on the optimal response system,genetic diversity and genetic structur e of 45 wild populations were analyzed by using 12 pairs of SSR primers.The results showed that the wild populations showed high genetic diversity at species level and population level.The genetic diversity of the population with higher degree of fragmentation was higher than that of the population with lower degree of fragmentation.Setaira viridis population has a certain resistance to the isolation effect brought by the fragmentation of green Ian dscape.(4)There was no significant correlation between geographical distance(KM)a nd genetic distance(GD)matrices,but the relationship between geographical distance and genetic distance was not significant.There was no geographic al isolation between populations.There is no significant correlation between geographical distance(KM)and gene flow(Nm)matrices,and the correlati on between geographical distance and gene flow is not significant.Geograp hical distance is not the main cause of gene flow changes.(5)The gene flow of the population with higher fragmentation degree is lower than that of the population with lower fragmentation degree.The population with higher fragmentation degree is affected by natural factors(topography,wind speed)or human disturbance(road),and the communication between populations is weaker than that of the population with lower fragmentation degree.The effect of gene flow between populations on the same side of t he river is higher than that on the other side of the river,and the river has a weak isolation effect on the population of Setaira viridis.Combining lan dscape characteristics and low-level gene flow around adjacent patches in th e study area,excluding geographical distance and geomorphological factors,the urban matrix has an impact on gene flow of Pennisetum davidianum po pulation.(6)There is a significant spatial genetic structure in the short distance of the p opulation.Landscape fragmentation can hinder gene flow,resulting in a sma ller spatial genetic structure distance. |
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