Genetic Diversity Analysis And Core Collection Construction Of Germplasm Of Sophora Moorcroftiana

Sophora moorcroftiana Benth.Baker is a native ornamental shrub species endemic to the Qinghai-Tibet Plateau.Its blue-purple inflorescence blooms into a large sea of pure flowers,making it a rare ornamental resource on the plateau.In addition,the special geographical location and ecological environment conditions of the QinghaiTibet Plateau provide a rich variation environment for this ornamental species.In recent years,due to excessive human disturbance,extreme climate,geographical separation and other adverse factors,the population of S.moorcroftiana have been seriously degraded and decreased sharply.At present,S.moorcroftiana are still completely in the wild state,which undoubtedly aggravates the loss of germplasm resources of S.moorcroftiana.In this study,300 representative samples of S.moorcroftiana were used as experimental materials.The core collections were constructed based on morphological traits and genetic diversity with SSR markers.The construction of core collection of S.moorcroftiana will lay a solid foundation for the protection and sustainable development of wild resources.The main results are as follows:(1)The genetic variation of the morphological characters of S.moorcroftiana resources was abundant.Among the 13 morphological characters of S.moorcroftiana resources,the coefficient of variation of base diameter,crown width,inflorescence length and seed number were 55%,47%,35% and 35%,respectively.The variation coefficients of 1000-seed weight,lobule number,pod length and leaf width were 13%,13%,16% and 21%,respectively.In addition,there was a great difference in morphological characters among different populations.Among the 15 populations,GG population had the highest coefficient of variation(27%),while MR and RB populations had the lowest coefficient of variation(17%).Therefore,the genetic diversity of S.moorcroftiana is widely distributed,which is suitable for the construction of core collection.(2)Twenty pairs of highly polymorphic SSR primers were filtrated based on partial nuclear genome of S.moorcroftiana.The average number of alleles detected in 300 representative samples was 4.8.The PIC value of 20 pairs of SSR primers ranged from0.0099 to 0.9142,with an average value of 0.5394.Among them,PIC values of 11primers(55%)were higher than average 0.5394.At population level,these 20 pairs of primers revealed that the percentage of polymorphic loci(PPL)ranged from 80% to95.00%,the number of alleles(Na)ranged from 3.70 to 5.50,and the number of effective alleles ranged from 2.266 to 3.250,Shannon’s information index(I)ranged from 0.816 to 1.118,the observed heterozygosity(Ho)ranged from 0.516 to 0.648,and the expected heterozygosity(He)ranged from 0.437 to 0.539.The genetic differentiation coefficients between the natural populations of S.moorcroftiana ranged from 0.017 to 0.179,and the genetic differentiation between JD and XTM populations was the largest,while the genetic differentiation between LZX and NML populations was the smallest.The gene flow ranged from 0.181 to 4.303,with the largest gene flow between LZX and NML populations and the smallest gene flow between JD and XTM populations.The genetic distance between populations of S.moorcroftiana was 0.033 to 0.472,and the average genetic distance between populations was 0.191.The genetic consistency ranged from 0.624 to 0.967,with an average of 0.831.The analysis of molecular variance(AMOVA)of natural populations showed that 12% of genetic variation existed among populations and 88% existed within individuals of S.moorcroftiana.In addition,population structure analysis divided these 300 representative samples of S.moorcroftiana into two groups.(3)Based on the morphological data and genetic diversity data with SSR markers,38 core collections were obtained by using the method of loci sampling and Nei’s genetic distance clustering.The percentage of retained morphological traits of core collections was 97.12%,the percentage of mean difference was 0,the percentage of variance difference was 7.69%,the range coincidence rate was 85.08%,and the variation rate of coefficient of variation was 107.31%.T test showed that there was no significant difference between core collections and the original collections in morphological traits.In addition,t test shows that the 20 loci of core collections in the average number of alleles,effective number of alleles,the percentage of polymorphic loci,Nei’s genetic diversity index,Shannon’s information index,the observed heterozygosity and expected heterozygosity germplasm had no significant difference with the original.Principal component analysis concluded that the core collections and original collections exist high genetic similarity.Therefore,core collections can also represent the genetic diversity of the original collections at the molecular level.In conclusion,this study revealed morphological characteristics and variation degree of S.moorcroftiana in different populations through the study of morphological diversity.In addition,it also revealed the degree of genetic variation and genetic diversity of S.moorcroftiana in different populations through SSR molecular marker technology.The core collections were constructed based on morphological diversity and genetic diversity,which laid a solid foundation for the protection and sustainable development of S.moorcroftiana wild resources.