The Influencing Mechanism Of Different Establishment Methods In Cutting Orchard On Rejuvenation For Vegetative Propagation Of Cunninghamia Lanceolata

Vegetative propagation can maintain excellent quality and speed up the rate of reproduction,which plays an important role in establishing sustainable and stable production forestry.However,the reproduction ability decreased with the aging of ontogeny.Therefore,the reversal of maturation or maintaining of the juvenile stage is of great practical significance for tree production and clonal reproduction of improved species.Chinese fir [Cunninghamia lanceolata(Lamb.)Hook.] is one of the most important native and evergreen coniferous timber species in subtropical China.Chinese fir plantations account for 30% of the total plantation area in China.Propagation via cuttings plays an important role in establishing sustainable and stable production forestry.The establishment and development of cutting orchard has become an important way to accelerate the planting of Chinese fir.The yield and quality of cuttings in cutting orchard directly affect the quality and production scale of Chinese fir clone seedlings.Therefore,the establishment of a new and efficient cutting orchard is conducive to improve afforestation and the development of Chinese fir industry.In this study,there are five propagules,they are tree canopy shoots of mother tree in holding trunk cutting orchard,cuttings from cutting surface in holding trunk cutting orchard,tree canopy shoots of mother tree in burying trunk method with crown cutting orchard,cuttings from cutting surface in burying trunk method with crown cutting orchard,and top tips cuttings of seedlings derived from seeds of the same parent tree,respectively.Five kinds of cuttings were collected for rooting experiment.In addition,the growth and physiological characteristics of cuttings cultured by cuttings from cutting surface in two kinds of cutting orchard were studied,and the seedlings was taken as the control treatment.From the aspects of phenotype,physiology and transcriptome,the rooting characteristics of cuttings and seedling growth of cuttings in different ways of cutting orchard were analyzed,and the influencing mechanism of cutting rooting and seedling growth of cuttings was explored,which was helpful for the research on the mechanism rejuvenation of Chinese fir.The main research results were as follows:1.The rooting type of Chinese fir cuttings under different treatments were callus rooting and barking rooting.The rooting rate of the cuttings from cutting surface in the cutting orchard of burying trunk method with crown(TCC),the cutting orchard of holding trunk(HTC)and seedlings(CKC)were significantly higher than the cuttings in crown of mother trees in two kinds of cutting orchard(HTCC,TCCC).The rooting coefficient of the cuttings from cutting surface in the cutting orchard of burying trunk method with crown was significantly higher than other cuttings,the rooting coefficient of the cutting in crown of mother trees in cutting orchard of holding trunk was significantly lower than other cuttings.In terms of overall rooting ability,TCC performed best,indicating it has better rejuvenation effect.The main factors affecting rooting ability were the K,t Z,t ZR,ABA,SOD,CAT,SC of cuttings leaf,JA,JA-Ile,APX,SC,IAA of cuttings stem phloem.SOD and CAT of cutting leaf positively regulated rooting ability of cuttings,while K,t Z,t ZR,ABA and SC negatively regulated rooting ability.IAA,SC and APX of cuttings stem phloem positively regulated rooting ability,while JA and JA-ILE negatively regulated rooting ability.After 110 days of cutting experiment,there was a significant positive correlation between rooting ability and stem phloem IAA,and a significant negative correlation between rooting ability and ABA.2.Transcriptome analysis was performed on roots under different treatments and a total of 59267 unigenes were obtained.The differentially expressed genes were analyzed by GO and KEGG functional enrichment,and WGCNA was also performed.The results showed that plant hormone signal transduction,terpenoid backbone biosynthesis,phenylpropanoid biosynthesis,and flavonoid biosynthesis may play important role in roots growth.The genes involved in the plant hormone signal pathway showed different regulation.These genes CCR,CAD,POX,HCT involved in lignin synthesis in phenylpropanoid biosynthesis were upregulated to promote root development.The F3’H and DFR were up-regulated and ANS down-regulated in flavonoid biosynthesis.These genes DXR,MCS,HDS,and GPPS in the terpenoid backbone biosynthesis pathway were up-regulated,which contributed to the formation of terpenoid precursors and influenced root development.This study provide theoretical reference for revealing root development for cuttings from different cutting orchard,and lay a theoretical foundation for the establishment of efficient cutting orchard,seedling breeding technology system of Chinese fir,and contribute to further exploring the rejuvenation mechanism of Chinese fir.3.The height,ground diameter and biomass of TC and CK were significantly higher than HT.The LA of HT and TC were significantly higher than CK,the SLA of HT was significantly higher than CK and TC,the LTD of CK was significantly higher than HT.The SV and SWD of TC and CK were significantly higher than HT.Through similarity analysis of growth characteristics and phenotypic trait sets,the results showed that there was similarity between TC and CK,both of which were significantly different from HT,indicating that TC has better rejuvenation effect than HT.The main factors affecting the growth of cutting seedlings are nutrients,hormone characteristics,anatomical structure and so on.Stem carbon content positively affected seedling growth and development.Because IAA synthesized from leaves was transported through phloem,IAA in TC stem was significantly higher than HT.JA inhibit plant growth,and leave,stem JA and JA-Ile in HT were higher than TC and CK.The LET and Gs of TC and CK were higher than HT,which was conducive to plant photosynthesis to promote seedling growth.The antioxidant enzymes as a marker of rejuvenation for Chinese fir cuttings need further study.On the whole,there were significant differences among the growth characteristics of different treatments.Phenotypic characteristics,nutrient characteristics and anatomical structure had positive effects on the growth of cutting seedlings,while hormone had negative effects on the growth of cutting seedlings.4.Transcriptome analysis was performed on the leaves and stem of cutting seedlings and a total of 99886 unigenes were obtained.The DEGs were analyzed by GO and KEGG functional enrichment,and GSEA functional enrichment analysis was performed for all genes in different comparison groups.The metabolism-related pathways such as“plant hormone signal transduction” and “starch and sucrose metabolism” were involved in the growth of Chinese fir seedlings.The rooting rate,rooting coefficient were positively correlated with leaf soluble sugar in root growth period.The rooting coefficient was negatively correlated with leaf starch,and was positively correlated with stem starch in initial cutting period.The "starch and sucrose metabolism" and "plant hormone signaling" are involved in leave development,the main genes involved in the pathway of starch and sucrose metabolism are SUS,beta-amylase and beta-glucosidase,the main genes involved in plant hormone and signal transduction pathway are the genes encoding B-ARR,PP2 C,JAZ.Pathways such as "starch and sucrose metabolism" and "plant pathogen interaction" are involved in stem development,the main genes involved in "starch and sucrose metabolism" are WAXY,GBE1,SUS,ots B.Most of these genes promote the synthesis of sucrose and trehalose,promote the transition from juvenile to adult,and negatively regulate plant rejuvenation.Genes involved in the "plant pathogen interaction" pathway were mainly the genes encoding RPM1,PBS1,KCS.Up-regulated of these genes are conducive to the enhancement of plant disease resistance and defense,and promote plant growth.The results provide theoretical reference for revealing the cuttings growth and rejuvenation mechanism from cuttings in different cutting orchard.5.Different treatments had significant positive effects on key genes of phenylpropanoid biosynthesis,key genes of terpenoid backbone biosynthesis and antioxidant enzymes,and then positively regulated root development.In particular,the key genes of phenylpropanoid biosynthesis promote lignin formation and directly influence root development.Key genes of plant hormone signaling pathway affect root development by significantly influencing hormone content.6.The growth of cuttings seedlings was directly affected by plant nutrients.Different establishment methods of cutting orchard directly significantly affected the changes of key genes in plant-pathogen interaction and indirectly affected the growth of cutting seedlings.Different establishment methods of cutting orchard also indirectly affected the growth of cutting seedlings by directly significantly affecting the changes of key genes in plant hormone signal transduction.In conclusion,compared with holding trunk cutting orchard,burying trunk method with crown cutting orchard can improve the rooting ability and promote seedlings growth.In this study,the rejuvenation mechanism of Chinese fir was studied from two aspects:“The influencing mechanism of different establishment methods in cutting orchard on cutting rooting for vegetative propagation of Cunninghamia lanceolata ”,and “The influencing mechanism of different establishment methods in cutting orchard on cutting seedling growth for vegetative propagation of Cunninghamia lanceolata ”.This study lay a theoretical foundation for the breakthrough of excellent seedling cultivation technology,and contribute to the promotion of Chinese fir industry development.