| The genus Litsea Lam.(Lauraceae)with more than 200 species around the world,mainly distributed in tropical and subtropical regions,and 72 species in China.It is woody plant taxa with wide distribution,multipurpose,significant ecological and economic value,which occupies important position in forest plant research.The Sect.Tomingodaphne plants of Litsea have important research value in industrial oil,medicine and essential oil exploitation and utilization.Tomingodaphne plants in Litsea.So far,the fruit essential oils extracted from L.cubeba,L.cubeba var.formosana and L.mollis have been widely used in traditional Chinese medicine,natural spices and inhibitor,but the differences in essential oil composition and quality among different species deserve further investigation.However,the species of this plant group are similar in morphology and function,but the phylogenetic relationship and phylogenetic position of each species is still a mystery,which hinder the application of Sect.In this study,the Sect.Tomingodaphne plants of Litsea were used as research materials.The taxonomic system of this plant taxa was improved by morphological and molecular systematics.The similarities and differences of chemical constituents among the species were analyzed by chemical fingerprints.The inhibitory activities and chemical compositions of essential oils from L.cubeba,L.cubeba var.formosana and L.mollis were further investigated.The data provided a basis for the development and utilization of Sect.Tomingodaphne plants.The main results were as follows:(1)Morphological identification of Sect.Tomingodaphne plants: Samples of Sect.Tomingodaphne plants were collected nationwide.A total of 15 species of Sect.Tomingodaphne plants were made in exsiccate specimens for further identification.All the specimens were reserved in the Institute of Subtropical Forestry,Chinese Academy of Forestry.In the traditional morphological classification study,L.auriculata and L.populifolia are divided into a group with the petioles more than 2 cm;L.cubeba,L.rubescens,L.ichangensis and L.chunii are divided into a group with the branchlets glabrous;according to the shortpubescence of twigs and leaves,L.moupinensis var.szechuanica,L.moupinensis,L.moupinensis var.glabrescens,L.cubeba var.formosana,L.euosma and L.mollis are divided into a group;L.pungens,L.sericea and L.veitchiana are divided into a group according to the long sericeous hairs on the twigs and leaves.(2)Phylogenetic analysis on Sect.Tomingodaphne plants in Litsea.Genome-wide re-sequencing and single nucleotide polymorphism(SNP)were carried out for 16 species in Sect.Tomingodaphne plants,2 Sect.Conodaphne plants,2 Sect.Cylicodaphne plants and 1outgroup(Sassafras tzumu).Then the chloroplast genome was assembled and spliced.The phylogenetic tree was constructed by SNP differential loci and chloroplast genome sequence,respectively.The two phylogenetic trees all showed that L.auriculata had a special position in the evolution of Litsea.In morphology,L.auriculata belongs to Sect.Tomingodaphne,but it has cup-shaped fruit holder.However,the phylogeny result indicated that L.auriculata had closer relationship with Sect.Cylicodaphne and Sect.Conodaphne.The results indicated that L.auriculata was a transitional specie between Sect.Cylicodaphne and Sect.Conodaphne,as well as a transitional specie between Sect.Tomingodaphne and evergreen trees.According to the phylogenetic analysis,the cup-shaped fruit holder could be used as an important basis for species classification in Litsea.Morever,L.cubeba,L.cubeba var.formosana,and L.mollis were clustered into one branch with fastest evolutionary rate.In addition,L.cubeba var.formosana was closer to L.mollis,which was quite different from morphological classification.(3)Chemical fingerprint analysis on Sect.Tomingodaphne plants in Litsea: The volatile components of fresh leaves in 12 Sect.Tomingodaphne plants were detected by Gas Chromatography-Mass Spectrometer(GC-MS).Based on the content of each component,cluster analysis was carried out using DPS(Data Processing System).There were 16 main components were identified,including ?.-Cubebene,?.-Farnesene,?.-Pinene,?.-elemene,?.-Myrcene,?.-Pinene,1,8-Cineole,Germacrene D,Linalool,Camphene,Ocimene,D-Limonene,Terpinene,Phellandrene and ?.-Terpineol.Based on the content of each component,cluster analysis for these samples was carried out by using DPS(Data Processing System)software.The results showed that the chemical constituents of L.auriculata werequite different from those of other species in Sect.Tomingodaphne,which was consistent with the results of morphological classification and phylogenetic classification.The chemical constituents of L.moupinensis var.glabrescens,L.moupinensis var.szechuanica and L.moupinensis were similar,which is consistent with the results of morphological classification.In addition,the volatile components of L.mollis,L.cubeba var.formosana and L.cubeba,clustered were similar and exhibited abundant varities.The inhibitory activities of essential oils from L.cubeba,L.cubeba var.formosana and L.mollis: According to the above experimental results,the essential oils of L.cubeba,L.cubeba var.formosana and L.mollis were selected as experimental materials to explore their inhibitory activities.The inhibition rate of essential oil against Fusarium oxysporum f.sp.fordii 1(Fof-1)was determined by growth rate method,and the antibacterial activities against Escherichia coli and Listeria monocytogenes by using the agar disc diffusion method.The results showed that the content of essential oil in L.cubeba was highest(6.13%)and the essential oil of L.cubeba was indicated that has extensive antimicrobial activity,which was superior over L.mollis and L.cubeba var.formosana whether in anti-bacteria or anti-fungal activities.The relative content of citral and linalool was showen signicantly correlated with the inhinition rate.(4)Population genetic diversity among L.populifolia in Mount Emei area.L.populifolia is the species owing the highest level of linalool in the Sect.Tomingodaphne plants.The genetic diversity of 84 leaf samples,which were collected from 7 different regions in Mount Emei area,was analyzed by genotyping-by-sequencing(GBS)technique.We identified 48,795 SNP sites globally and clustered the samples into three clusters.The average of Ho and He was0.27218 and 0.20635,respectively.As a result of ANOVA,the percentage of intra-group variation reached 96.28%,while inter-group variation was only 3.72%.These results indicated that regional divergence issued the main factor of genetic diversity among L.populifolia in Emei Mountain,and the different altitudes in high altitude area also affected the genetic diversity of intra-population.The high nucleotide diversity in the populations and the high percentage of intra-group variation illustrated that genetic variation of L.populifolia in MountEmei mainly exists in intra-population.Our data provided a fundamental basis for the genetic breeding and diversity conservation of L.populifolia. |
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