Research On Structural Diversity And Allelopathy Potential Of Endophytic Fungus Communities In Casuarina Equisetifolia Roots Of Various Ages Of Stand

A majority of studies regarding Casuarina equisetifolia protection forest focus on aspects like genetic breeding,seedling and afforestation,as well as degradation and allelopathy of litter.However,research on isolation and identification of endophytic fungi in Casuarina equisetifolia roots as well as their community structural diversity is lacking.Therefore,young,half-mature and mature Casuarina equisetifolia forests in Guilinyang coast were selected as the test plots in this paper based on the practical demand of Casuarina equisetifolia forest in Hainan Province.Abundance,community composition and evolutionary relationship among endophytic fungi in Casuarina equisetifolia roots of various ages of stand were analyzed using high throughput sequencing platform.Meanwhile,differences and the dynamic changes in endophytic fungus communities in Casuarina equisetifolia roots of various ages of stand were compared,so as to reveal the structural diversity of endophytic fungus community in Casuarina equisetifolia.Furthermore,endophytic fungi in Casuarina equisetifolia roots of various ages of stand were isolated,and strain identification was carried out in combination with Biolog microorganism automatic analysis system.The fermentation liquid of endophytic fungi of Casuarina equisetifolia was isolated and identified by GC-MS.The contents of the extracts were compared with those of the previous extracts of Casuarina equisetifolia,root,floor litter and soil leaching extract.And use different fermentation liquid on the treatment of Thespesia lampas L.and Calophyllum inophyllum L.,in order to explore the differences and effects of different fermentation liquid on allelopathic potential of native trees.The research results had established foundation for revealing the role of endophytic fungi in Casuarina equisetifolia roots in allelopathy.In addition,it had provided theoretical foundation for further investigating the mechanism and pathway of allelopathy of Casuarina equisetifolia,and scientific theoretical guidance for construction and update of protection forest in Hainan Province.The main results of this paper are as follows:1.Based on Illumina Miseq high-throughput sequencing platform,endophytic fungi of different forest age Casuarina equisetifolia root received 318972 valid sequence,the sequence number of endophytic fungi of Casuarina equisetifolia was as follows: mid-maturation forest,sapling forest,mature forest.Clustering tree and histogram portfolio analysis of various ages of stand indicated that young forest and half-mature forest were classified into the same cluster.It demonstrated that community compositions of young forest and half-mature forest were closer,which were different from that of mature forest.And endophytic fungi of Casuarina equisetifolia the dominant population are Ascomycota and Basidiomycota.PCA and PCoA analysis through OTU abundance indicated that great difference in structural composition of endophytic fungi in Casuarina equisetifolia roots of various ages of stand could be seen.Of them,age of stand was the major factor leading to discrete samples.2.The endophytic fungi of Casuarina equisetifolia were isolated by traditional classical method,and the growth of bacteria without fungi was tested by sterile water test and tissue blotting.Based on the biolog microbial automatic analysis system,four strains of fungi(two strains of Penicillium,two strains of Aspergillus)were identified as Aspergillus aculeatus lzuka,Penicillium melinii thom,Neosartorya fisccheri,Penicillium solitum westling BGB,all belong to Trichocomaceae,for the advantage of endophytic fungi of Casuarina equisetifolia root fungus.3.The results of GC-MS analysis show that the secondary metabolites of endophytic fungi from Casuarina equisetifolia at different ages are mainly esters,phenols,acids,ketones,aldehydes,ethers,alchhols,pyridine.There are differences in the types and contents of substances identified by different fermentation liquid.And compared with the root,floor litter and soil leaching extracted from Casuarina equisetifolia at various ages,have common product are 2,4-bis(1,1-dimethylethyl)-,1,2,3,4-Butanetetrol,(-)-Globulol and some difference product are 1,2,3-Benzenetriol,Dodecanoic acid,Hexadecanoi cacid,Octadecanoic acid.In addition,use methanol extraction material than n-hexane as an extractant identified species more abundant.4.Different endophytic fungi fermented liquid all have obvious inhibitory effect on Thespesia lampas L.and Calophyllum inophyllum L.,reduce the germination rate of native tree seeds.And the absolute germination rate,absolute germination potential and allelopathic effect index are also inhibited.In the same kind of fermentation liquid,the performance of the native tree species Calophyllum inophyllum L.than Thespesia lampas L.on the allelopathy of the more tolerant.In different fermentation liquid,Aspergillus aculeatus lzuka has the strongest inhibition effect.Suggests that allelochemicals kinds and content in the fermented liquid is one of the cause of inhibition.In conclusion,endophytic fungi of Casuarina equisetifolia showed rich flora diversity.There were differences in the structure of flora with the change of age,which was related to factors such as age of forest age,environmental factors of forest land and accumulation of allelochemicals in forest land.In addition,there were some allelopathic substances in the secondary metabolites of endophytic fungi in different ages,and the fermentation liquid had different inhibitory effects on the seeds of native tree species.Indicating that microbial secondary metabolites are an important aspect of the source of allelochemicals.