| Plant-microbial remediation has been recognized to be one of the most economical,green and promising remediation technique in mining area,especially some local dominant woody plants with large biomass,fast growth,strong adaptability and certain economic value have brought into sharp focus on the treatment of heavy metal pollution in mining ponds.During the previous investigation in the Huangmaoshan tailing ponds of Gejiu,Yunnan,we found that Sailz matsudana(S.matsudana),Salix matsudana var.matsudana f.tortuosa(S.m.f.tortuosa),Cupressus duclouxiana(C.duclouxiana),Phyllostachys viridis(P.viridis)were the dominant plants in the investigated area.In this paper,these four woody plants were taken as research objects.The capacity to alleviate the four plants against heavy metals was estimated by the analysis of their heavy metal accumulation characteristics as well as soil physicochemical properties.The diversity of dark septate endophyte(DSE),a functional microorganism colonizing in plant roots,was studied by microbial pure culture technology;the fungal diversity in roots was explored by high-throughput sequencing technology.The cadmium tolerance,siderphore production and phosphorus dissolving ability of DSE representative strains was estimated in vitro.The conclusions were displayed as below:(1)In the mining ponds where heavy metal pollution was serious,the above four plants all grew well and formed the dominant species in the investigated area.The concentrations of heavy metals in different organs of the plants,as well as the bioaccumulation factor(BCF)and translocation factor(TF)were analyzed.None of the four woody species belonged to hyperaccumulators of Pb,Zn and Cd;The BCF of Zn and Cd in S.matsudana and S.m.f.tortuosa were 2.58,2.57 and 3.02,1.57 respectively.It was worth mentioning that two kinds of willows showed higher ability of Cd transfer to twig,and their TF were 6.458,5.044,respectively.The two kinds of willows had higher ability to transfer Cd to leave,and their TF were as high as 16.330 and 4.879.It can be seen that S.matsudana and S.m.f.tortuosa have strong ability to accumulate and transfer Zn and Cd.In addition,the ability of Pb accumulation of the four plants was not high,the ability to accumulate and transfer Zn and Cd of S.matsudana and S.m.f.tortuosa was also not high,Therefore,we think that S.matsudana and S.m.f.tortuosa belong to the metal tolerance type of plants,while C.duclouxiana and P.viridis belong to the metal exclusion type of plants.(2)A total of 397 DSE strains was obtained from the four plant roots by pure culture isolation technique.Among them,165 strains(accounting for 42%)was isolated from S.matsudana,56 strains(accounting for 14%)from S.m.f.tortuosa,115 strains(accounting for 29%)from P.viridis and 61 strains(accounting for 15%)from C.duclouxiana.The 397 DSE strains was classified into 30 clades on the phylogenetic tree,with eight clades shared among four woody species,and the dominant groups accounting for more than 10% of the 397 DSE strains was Cladosporium spp.,Paraphoma spp.and Phialophora spp.In addition,P.viridis had the highest DSE richness of fungi within its roots,with 23 clades and 8 unique clades.Whereas,the DSE richness of C.duclouxiana was the lowest among the four plants,with its optimal fungal group Cladosporium spp.accounted for up to 45.90% and was absolutely dominant.The rank order of DSE richness was as follows: P.viridis > S.m.f.tortuosa >S.matsudana > C.duclouxiana.(3)The fungal diversity in roots was explored by high-throughput sequencing technology.It was found that the richness coefficient of C.duclouxiana and S.m.f.tortuosa was higher than those of S.matsudana,and significantly higher than those of P.viridis.There was no significant difference in the diversity coefficient of the four plants.Species composition analysis showed that 93%-98% of the fungi in the roots of the four plants belonged to Ascomycota and Basidiomycota,especially Ascomycota(accounting for 78%-86%)were absolutely dominant.The difference of dominant fungi groups(accounting for more than 1%)in the roots of the four plants was obvious at the genus level.Except for the common dominant groups(unclassified?o?Helotiales,Dactylonectria,unclassified?f?Herpotrichiellaceae and unclassified?p?Ascomycota)shared by the four woody,We found some degree of divergence between the composition and the ratio of the dominant fungal taxa within the roots of the four plants,PCoA analysis further illustrated the significant difference in the distribution of fungi within the roots of the four species.Species diversity analysis found unclassified?o?Helotiales,unclassified?p?Ascomycota,Paraphoma spp.and Rhizoctonia spp.was significantly different among the four plants.In addition,the correlation analysis of environmental factors demonstrated that the heavy metal pollution had a lower impact on the composition of microbial group than the soil nutrients in the environment with serious heavy metal pollution in the mining area.The most important environment factor was nitrogen concentration,followed by organic matter,available phosphorus,and the least impact on the microbial group was potassium concentration.(4)The cadmium tolerance,siderophore production,and phosphorus solubility was evaluated in the nine representative strains,which were 527(Cladosporium sp.),679(Periconia sp.),127(Phialophora sp.),236(Minimelanolocus sp.),795(Minimelanolocus sp.),376(Exophiala sp.),104(Leptosphaeria sp.),584(Pyrenochaeta sp.)and 327(Paraphoma sp.),Among them,the host plants of the remaining strains was S.matsudana,except for strain 795,which was isolated from S.m.f.tortuosa,and strain 376,which was isolated from P.viridis.The cadmium tolerance experiments showed that 376,104,584 and 327 had high Cd tolerance,and they could grow at a Cd concentration of 500 mg/L;Siderophore experiments showed that all of the nine strains had the ability to produce siderophore,among which strain 104 was the strongest of the nine strains;Phosphorus solubility experiments showed that 327,127 and 376 had a strong ability to dissolve phosphorus,strain 327 had higher biomass,mycelium phosphorus concentration and fermentation broth phosphorus concentration which was the most prominent among the 9 strains.The above research results and conclusions provide basic data for phytoremediation of heavy metal mining areas with the four plants,and also provide basic information and strain resources of endophytic fungi for plant-microbial remediation with the four plants. |
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