Study On The Composition Of Rhizosphere Fungal Communities And The Functions Of Some Cultivable Fungi In Pioneer Plants In Phosphate Mine Reclamation Areas

The degradation of phosphate rock mountainous areas poses a serious threat to the ecological security of the mountainous system in southwestern China.Plants and microorganisms can form complex symbiotic relationships,which can help improve the overall stability of the ecosystem.However,the "plant-microbial" characteristics still lack in-depth understanding.The structure and functional characteristics of rhizosphere/root microbiota communities reflect changes in environmental stress.In view of this,this study conducted the isolation and identification of culturable fungi through high-throughput sequencing technology and traditional dilution coating method,analyzed the composition and diversity of rhizosphere fungal community in the phosphate rock reclamation area,and explored its correlation with soil environmental factors,laying the foundation for developing unique functional strains in the area and building a rhizosphere beneficial fungal species bank.Dominant culturable probiotic fungi has similar biological functions to mycorrhizal fungi and plays a more important role in stress environments.However,there are few reports on the promotion of growth of Lolium perenne and Medicago sativa by this fungus.Due to the presence of chelating systems and metal chelating abilities,probiotic fungi can alleviate cadmium(Cd)stress and form symbiotic relationships with most plants.Therefore,this study used quartz sand as a culture medium and analyzed the effects of inoculation of probiotic fungi on the growth,root characteristics,and antioxidant enzyme system of Lolium perenne and Medicago sativa under Cd stress through a pot experiment.It is expected to provide certain scientific reference significance for the planting and actual production of Lolium perenne and Medicago sativa in the Cd contaminated soil around the mining area.The main results obtained are as follows:1.Based on high throughput research on the characteristics of rhizosphere fungi,ITS gene sequence analysis was conducted for rhizosphere fungi.The main fungal genera in the natural and artificial restoration areas were Mortierella,Knufia,Cladosporium,and Exophylla.The main fungal genera in the natural recovery area are Ruhlandiella,Archaeorhizomyces,Clavaria,Cladophialophora,Trichoderma,Coniosporium,Paraboeremia,Tritirachium,Beauveria.The main fungal genera in the artificial restoration area are Thelebolus,Sesquicillium,Cylindromonium,Talaromyces,and Hygrocybe.2.Based on the isolation and identification of rhizosphere fungi from pioneer plants,46 strains of rhizosphere fungi were purified using traditional isolation and culture methods.46 strains of rhizosphere fungi belong to 6 classes,10 orders,13 families,17 genera,and 28 species.The fungi isolated and identified in the natural recovery zone belong to 12 genera and 21 species,and the dominant groups are Penicillium(25.00%),Paecilomyces(25.00%),Talaromyces(14.29%),Cladosporium(7.14%).The fungi isolated and identified in the artificial recovery zone belong to 6 genera and 9 species,and the dominant groups are Purpuricillium(38.89%),Penicillium(27.78%),Metarhizium(11.11%)and Mortierella(11.11%).Penicillium is widely distributed in two sample plots.It is worth noting that in the artificially restored areas,although the diversity of culturable fungi isolated was low,the proportion of beneficial fungi was significantly higher than in the naturally restored areas.3.Redundancy analysis(RDA)was conducted between the relative abundance of rhizosphere fungi and soil physical and chemical indicators,and it was concluded that there was a significant positive correlation between total phosphorus and alkaline nitrogen in the soil of the artificial restoration area and the rhizosphere fungal community;There was a significant positive correlation between soil organic matter and p H and rhizosphere fungal communities in natural restoration areas.The composition of rhizosphere fungal community in this reclamation area was significantly correlated with soil alkaline nitrogen and soil p H(P<0.05).4.The results of seed germination experiments showed that after inoculation with Paraboeremia putaminum bacterial solution,the germination index,vitality index,and total fresh weight of Medicago sativa seeds significantly increased by 61.93%,85.58%,and 25.57%,respectively.After inoculation with Aureobasidium pullulans,the germination rate,vitality index,plant height,root length,and total fresh weight of alfalfa seeds significantly decreased by 11.32%,81.57%,55.03%,82.48%,and 59.02%,respectively.5.Inoculation P.putaminum can increase the root length,dry weight,root surface area,root volume,branch number,and root tip number of Lolium perenne and Medicago sativa,and promote the growth and development of Lolium perenne and Medicago sativa.Under Cd stress,inoculate P.putaminum can increase the root length,total root length,root volume,root tip number,shoot SOD activity,and shoot POD activity of Lolium perenne.Inoculation under Cd stress P.putaminum can increase the aboveground fresh weight,total root length,branch number,root tip number,total chlorophyll content,underground SOD content,and MDA content of Medicago sativa.The characteristics of the composition and diversity of rhizosphere fungal communities obtained in this study,as well as the analysis results of microbial communities and environmental factors,are of great significance for the development and utilization of beneficial microbial resources,and can provide a theoretical basis for the restoration of phosphorus rich land.The dominant probiotic fungus P.putaminum strain selected in this study is a strain with good growth promoting effect on Lolium perenne and Medicago sativa,in order to provide a basis for further revealing the mechanism of improving plant heavy metal stress tolerance and improving the ecological role of soil microenvironment in agricultural heavy metal polluted areas by using dominant fungal resources.