Genetic Relationship And Diversity Analysis Of Lagerstroemia Based On SSR Markers

Lagerstroemia indica is a perennial deciduous shrub or small tree belonging to the genus Lagerstroemia in the Lythraceae.Lagerstroemia indica has a long history of cultivation,and has the advantages of rich color,gorgeous,long flowering period,anti-pollution and other advantages.It has been widely used in garden landscape and greening work.With the increasing number of new varieties of Lagerstroemia indica,there are confusion in variety management and difficulty in variety identification,which seriously hinders the development of Lagerstroemia indica.In this study,SSR loci of Lagerstroemia indica were analyzed based on leaf transcriptome data,primers suitable for SSR analysis were designed and screened,the genetic relationships and genetic diversity of 97 Lagerstroemia indica cultivars or species were evaluated,and their fingerprints were constructed,which provided a scientific basis for the identification and protection of Lagerstroemia indica cultivars or species.The results of this study are as follows:(1)Transcriptome sequencing of young and mature leaves of Lagerstroemia indica varieties ’Dynamite’ and’Ebony Embers’ revealed that 12,901 transcripts containing SSR sites were found from 44,440 transcripts with a length greater than 500 bp,accounting for 29.03%.A total of 15,275 SSR sites were detected,including 13,844 SSR sites in the perfect repeat form(P-type),accounting for 90.63%,and 1,431 SSR sites in the complex repeat unit(C-type),accounting for 9.37%.Among the P-type SSR sites,the SSR sites of single nucleotide repeat(P1 type),dinucleotide repeat(P2 type)and trinucleotide repeat(P3 type)were the most abundant,accounting for 88.58%.(2)According to the transcript sequence information,12,882 pairs of SSR primers were successfully designed,and the primer design success rate was 84.33%.Twenty-four pairs of primers with clear amplification band,good polymorphism and stability were selected from 300 pairs of primers randomly selected.In 97 Lagerstroemia indica cultivars(species),24 pairs of SSR primers detected a total of 535 amplification sites,the percentage of primer polymorphism sites reached 100%,and the Shannon information index(Ⅰ)was between 0 and 3.774.The degree of zygosity(Ho)is between 0 and 0.584,and the expected degree of heterozygosity(He)is between 0.021 and 0.972.Among them,the expected degree of heterozygosity(He)of 24 pairs of primers is higher than the observed degree of heterozygosity(Ho),accounting for about 100%.%,the gene diversity index(G)was between 0.08 and 0.972,and the polymorphism information content(PIC)was between 0.078 and 0.970,with an average value of 0.586.The results indicated that all 24 pairs of SSR primers obtained by screening could amplify 97 Lagerstroemia indica varieties well,and provided suitable primers for cultivar identification,relationship analysis and genetic diversity research of Lagerstroemia indica.(3)The genetic relationship analysis of 97 Lagerstroemia indica varieties or species found that 97 Lagerstroemia indica varieties or species were clustered into 9 groups.Among the 7 wild species of Lagerstroemia indica,Lagerstroemia balansae Koehne,Lagerstroemia limii,Lagerstroemia micrantha Merr,Lagerstroemia speciosa,Lagerstroemia excelsa Chun were clustered in group I,and Lagerstroemia caudata and Lagerstroemia fauriei Koehne were clustered in group VII.The clustering results show that these The wild species of Lagerstroemia indica is in a relatively primitive position in evolution.In the long-term cross-breeding work of Lagerstroemia indica,the wild species as parents have widely participated in the breeding process of new varieties of Lagerstroemia indica.Among the 97 Lagerstroemia indica varieties(species),the Lagerstroemia indica varieties from Florida are clustered in 9 groups,and the research on the development and utilization of new Lagerstroemia indica varieties in the United States started early.Many Lagerstroemia indica resources have been collected from all over the world,and a large number of Cross-breeding experiments have produced many new plant varieties.(4)The total inbreeding number(Fit),population inbreeding number(Fis),genetic differentiation coefficient(Fst),gene flow(Nm)and total inbreeding number(Fit)were 0.841,0.832,0.054 and 4.362,respectively.The genetic differentiation of the 9 groups of Lagerstroemia indica is very low,and the gene flow and the genetic stability of the population are very high.AMOVE analysis showed that the genetic variation of the 9 groups mainly came from within the group,with a coefficient of variation of 7.751,accounting for 79%of the total variation,while the lowest variation among the groups was only 5%.It may be related to the way of breeding new varieties of Lagerstroemia indica.Artificial cross-breeding strengthens the gene exchange between Lagerstroemia indica varieties or species,which is the main reason for the low genetic differentiation among Lagerstroemia indica varieties or species.(5)The discriminant ability of the 15 pairs of primers with the best polymorphism was evaluated.The discriminant ability of primer SSR292 was the strongest,and a total of 58 varieties or species were identified,followed by primer SSR132,SSR174 and SSR102,and primer SSR293 and SSR269 had the least number of discriminants.Using the primer combination method,6 core primers were successfully identified for 97 Lagerstroemia indica varieties or species,namely SSR292,SSR132,SSR102,SSR289,SSR107 and SSR211.The DNA fingerprints of 97 cultivars or species were successfully constructed by using the core primers,and converted into fingerprint QR codes.For the first time,a DNA molecular ID card containing a relatively comprehensive variety of Lagerstroemia indica was established,which laid the foundation for the establishment of a standard fingerprint database platform for Lagerstroemia indica.It provides a scientific basis for the identification and protection of Lagerstroemia indica varieties or species.