| Tricholoma matsutake(S.Ito&S.Imai)Singer is a kind of ectomycorrhizal fungi,which plays an important role in the forest ecosystem.T.matsutake is popular for its unique edible and medicinal value,but it cannot be cultivated artificially at present.The germplasm resources of T.matsutake are decreasing year by year due to the contradiction between supply and demand,and now it is in a vulnerable state.It will provide theoretical basis for the conservation of germplasm resources when the correlations were clarified between the distribution of T.matsutake and microecological factors.In this paper,based on the habitat of T.matsutake in Northeast China,some methods of high-throughput sequencing,bioinformatics and statistics were used to analyze the changes of microbial communities and functions,the correlations between microbial communities and soil physicochemical factors.Two habitats of T.matsutake were selected as the study plots,they are respectively a mixed forest of Quercus mongolica Fisch.ex Ledeb with Rhododendron simsii Planch.(sample plot B)and a mixed forest of Q.mongolica,R.simsii and Pinus densiflora Sieb.et Zucc.(sample plot C),and a control plot with a pure forest of Q.mongolica(sample plot A)at the same latitude as sample plot B.The main results were shown follows.(1)The diversity indexes,species composition structure and functions of the fungal community in the habitat of T.matsutake showed a certain dynamic change rule.In plot B,plot C and plot A,the fungal alpha diversity indexes showed difference with the sampling time,with significant(p<0.05)higher diversity in June to July than in August to September.There was highest diversity in plot C and some alpha diversity indexes showed significant differences between plots.Beta diversity analysis of the three plots showed separately,and the community composition of plot B and plot C were relatively close.The fungal communities in the same plot were comparatively closer.Fungal ASVs from soil were annotated to 11 phyla,44 classes,105 orders,222 families and 423 genera.Species composition and relative abundance varied with sampling time and plot.The dominant genera at plot A in June to July were Russula(33.77%),Cortinarius(26.09%),Sebacina(8.77%)and Mortierella(4.53%)etc.The dominant genera in August to Septembe were Russula(64.79%),Mortierella(18.42%),Cortinarius(6.43%)and Tomentella(3.90%)etc.The dominant genera at plot B in June to July were Russula(32.39%),Cortinarius(16.34%),Hygrophorus(6.05%)and Sistotrema(5.14%)etc.Tricholoma(42.16%),Umbelopsis(23.55%),Russula(18.07%)and Mortierella(2.90%)were the dominant genera in August to September.The dominant genera at plot C in June to July were Russula(24.54%),Mortierella(9.32%),Delastria(6.51%)and Umbelopsis(6.43%)etc.Russula(39.92%),Hydnellum(37.49%),Umbelopsis(2.16%)and Sebacina(2.10%)were the dominant genera in August to September.Through the analysis,we found that the biomakers were different among the plots.In plot B,Mortierellomycota,Tricholoma and Umbelopsis were the fungal biomarker,while in plot C,Hydnellum was the fungal biomarker.The function of soil fungi was predicted by PICRUST2,and five primary metabolic pathways were obtained,and there was no change in sampling site and sampling time.A total of 29 secondary metabolic pathways were obtained.In the early of development stage,plot B and plot C showed similar pathway compositions.The results showed of the group involved in nitrogen fixation metabolism in the tertiary pathway that Russula,Cortinarius and Sebacina were the nitrogen fixation fungi.(2)The diversity indexes,species composition and functions of the bacterial community in the habitat of T.matsutake were shown as follows.In plot B,plot C and plot A,the bacterial alpha diversity indexes showed difference with the sampling time,with significant(p<0.05)higher diversity in June to July than in August to September.There was highest diversity in plot A and some alpha diversity indexes showed significant differences between plots.Beta diversity analysis of the three plots showed separately,and the bacterial communities in the same plot were comparatively closer.Bacterial ASVs from soil were attributed to 41 phyla,119 classes,284 orders,481 families,1021 genera.The dominant genera at plot A in August to September were Ochrobactrum(7.99%),Vibrionimonas(6.10%),Allonhizobium-NeorhizobiumPararhizobium-Rhizobium(2.72%),Candidatus?Udaeobacter(1.80%)and so on.The dominant genera at plot B in June to July were Burkholderia-CaballeroniaParaburkholderia(5.01%),Bryobacter(2.63%),Bradyrhizobium(2.52%),Acidothermus(2.25%)and so on.Burkholderia-Caballeronia-Paraburkholderia(21.24%),Bradyrhizobium(4.22%),Acidothermus(2.82%)and Bryobacter(2.36%)were the dominant genera in August to September.The dominant genera at plot C in June to July were Bradyrhizobium(4.35%),Burkholderia-CaballeroniaParaburkholderia(4.18%),Candidatus?Udaeobacter(3.66%)and Mycobacterium(2.83%),etc.The dominant genera at plot C in August to September were Bradyrhizobium(3.81%),Bryobacter(3.02%),Mycobacterium(2.38%),Burkholderiacaballeronia-Paraburkholderia(2.28%)and so on.The dominant genera at plot A in June to July were Subgroup?6(6.45%),Candidatus?Udaeobacter(5.44%),KD4-96(3.72%)and Bradyrhizobium(2.65%),etc.Through analysis,the bacterial biomarker in the fruit-body development period of the sample site B were Proteobacteria,Burkholderiaceae,and Burkholderia-Caballeronia-Paraburkholderia.PICRUST2 was used to predict the functions of soil bacteria,and five primary metabolic pathways were obtained.There was little difference in primary metabolic pathways among the three plots.A total of 61 secondary metabolic pathways were obtained.The metabolic pathways of plot B and plot C were similar.In three plots,the composition of soil bacterial pathways was similar in two growth stages of T.matsutake.Analysis of the tertiary metabolic pathway of ornithine cycle,a nitrogenfixing pathway,showed that both Bradyrhizobium are known nitrogen-fixing bacteria,and other bacterial genera,Acidothermus,Subgroup?6 and Subgroup?2 are also important nitrogen-fixing bacteria in soil.(3)Besides the difference of forest types,the SAK of plot A was significantly higher than that of other plots.Soil texture is different,plot A is loam,plot B and plot C are sandy clay.The results of redundancy analysis showed that Sp H and SAK were the most significant influencing factors(p<0.01)on the composition and distribution of soil fungal community,and other factors were also significant influencing factors(p<0.05),followed by SOM>SAP>SEN.Sp H was the most significant factor(p<0.01)affecting the composition and distribution of bacterial community in soil,and SEN was the most significant factor(p<0.05)affecting the composition and distribution of bacterial community.The content of sand,silt and clay in the soil was positively correlated with the composition of fungal and bacterial communities.(4)In the early stage of fruiting body development(in June to July)of T.matsutake,the relative abundance of Tricholoma in plot B was 1.33%,the fruiting body development stage of Tricholoma(in August to September),the relative abundance of Tricholoma in plot B increased rapidly to 42.35%,but the relative abundance of Tricholoma in plot C decreased from 3.64% to 0.10%.SOM,SEN and SAP were negatively correlated with Tricholoma,while SAK was positively correlated with Tricholoma.The content of clay in the soil had positively correlated with the abundance of Tricholoma,while that of silt was nearly negatively correlated.The composition of fungi and bacteria in the habitat soil had certain influence on the community composition of Tricholoma.The results of association network analysis showed that Umbelopsis,Dasyspora and other genera were positively correlated with Trichomoma,and their promoting effects on plants and fungi were also reported in some literature.However,fungi such as Russula,Inocybe and Leotia competed with Tricholoma,so the association network was negatively correlated.Among the bacteria,Burkholderia-Caballeronia-Paraburkholderia and Bradyrhizobium were positively correlated with Tricholoma in soil.Burkholderia and Rhizobium were known as mycorrhizal auxiliary bacteria.MND1,Phyllobacterium,Pseudoxanthomonas and Nitrospira were significantly negatively correlated with Tricholoma. |
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