| Angelica sinensis is extremely intolerant to the continuous cropping,and the cultivation of wasteland causes serious soil erosion,so it is urgent to find a crop residue soil to replace the uncultivated meadow soils.In the study,the crop residue soils of Triticum aestivum L.,Astragalus membranaceus(Fisch.)Bge.var.mongholicus(Bge.)Hsiao,Solanum tuberosum L.and Angelica sinensis(Oliv.)Diels were used to cultivate A.sinensis seedlings,and the A.sinensis seedlings in the uncultivated meadow soil were used as the control group.Using amplicon sequencing and microbial cultivable methods,I investigated the compositions and diversities of the bacterial and fungal communities,the dynamics of the microbial communities and the factors,and the relationships between microbial communities and factors to reveal the impact of the ecological factors on microbial communities.I hope that the results could provide a scientific basis for a reasonable residue soil instead of the uncultivated meadow soils and a regulating strategy to the microbial community.The main conclusions were summarized as follows:1.During the growth stages of A.sinensis seedlings,the dominant bacterial phyla included Proteobacteria,Bacteroidetes,Acidobacteria,and Plantomycetes,and the dominant fungal phyla included Proteobacteria,Bacteroidetes,Acidobacteria,and Plantomycetes.There were differences in the compositions of the dominant bacterial and fungal phyla during growth stages in the residue soils.Both the growth stages and the residue soils had different effects on the relative abundance of Proteobacteria,Bacteroidetes,Ascomycota,and Basidiomycota.The order of the number of CFU for bacteria,actinomycetes,and fungi during the growth stages was as follows: bacteria>actinomycetes>fungi.During the growth stages,the order of the average coefficients of variation for bacteria,actinomycetes and fungi was as follows: fungi>actinomycetes>bacteria.According to the preliminary identification of bacterial and fungal culture strains,12 strains belonged to Actinobacteria,eight strains to Proteobacteria,five strains to Firmicutes,one strain to Bacteroidetes,12 strains to Ascomycota,and four strains to Mucoromycota.2.Core bacterial and fungal OTUs for all residue soils were identified.The seedling growth stages in all residue soils significantly affected the core bacterial and fungal community compositions.Different residue soils significantly affected the neighborhood connectivity of the core bacterial community co-occurrence network and did not significantly affect that of the core fungal community co-occurrence network.Neighborhood connectivity of the core bacterial community in HQ was the highest in all reside soils.By analyzing the degree centrality of the core bacterial and fungal community co-occurrence networks,the key bacterial and fungal OTUs in different residues were determined.It was found that the key bacterial and fungal OTUs in different residue soils differed greatly from each other.The residue soils importantly affected the construction of the key bacterial and fungal OTUs.3.It is concluded that the bacterial community diversities of all residue soils had been stable before AM stage,and the fungal community diversities of DG and SH had been stable before AM stage.The of fungal community diversities in XM,HQ and MLS changed significantly during the growth stages.The bacterial community abundance in all residue soils changed significantly during the growth stages,while the fungal community abundance only in XM significantly changed.There were the specific bacteria and fungi during the growth stages,including 26 specific core bacteria,18 specific bacteria,three specific core fungi,and 16 specific fungi.There were 65% of the specific core bacteria and 63% of the specific fungal genus in SH.By comparing the SH with other residue soils,the bacteria and fungi that significant differeed at taxonomy levels were found.4.The changes in the composition of the bacterial and fungal communities during the growth stages were accompanied by changes in the composition of the core bacterial and fungal communities.Except for the fungal community of DG,the composition changes of the bacterial and fungal communities in the others were also accompanied by those in the potential functions of the bacterial and fungal communities.The bacterial communities and potential functions in the XM,HQ,MLS,and DG were not significantly different from each other,but significantly different from the SH.There were significant differences in the composition of the fungal communities between the residue soils,while the potential functions between the corresponding residue soils were not necessarily different.Rhizoctonia solani,one of the pathogenic fungi to A.sinensis,was found in all the residue soils.The highest relative abundance of R.solani in DG indicated the possible reasons that the high incidence morbidity and the severe root rot for A.sinensis occurred after transplanting A.sinensis seedlings cultivated in DG.R.solani is an opportunistic pathogen.The relative abundance of the ectomycorrhizal fungi and arbuscular mycorrhizal fungi in HQ was highest in all residue soils,which provided a strong evidence that the quality of A.sinensis seedlings cultivated in HQ was better than that in XH,MLS,and DG.5.During the succession of the bacterial and fungal communities in the A.sinensis seedlings,the niche overlap,narrow niche,and wide niche in bacterial and fungal species showed the stability and variability of the trend of the bacterial and fungal population in the A.sinensis seedling rhizosphere.The main factors affecting the formation of bacterial and fungal communities at distinct growth stages were different,the pH and T in AM,the RF in BM,and the MBC,MBN,RD,and PW in CM.These conclusions were a theoretical basis for the farmland management of A.sinensis seedlings,keeping warm after sowing the A.sinensis seeds,increasing irrigation timely in the middle of the growth period,and fertilizing organic fertilizers and nitrogen fertilizers in the middle and later growth period.The soil pH should be an index for selecting the reside soil sources.6.It was found that there was a close relationship between HQ and its factors,indicating bacterial and fungal communities could better adapt to the micro-environment in HQ.These were conducive to the succession of the bacterial and fungal communities during the growth stages.The seedling indices in the HQ were better than those in other crop residue soils,the relative abundance of ectomycorrhizal fungi and arbuscular mycorrhizal fungi were the highest in all residue soils,and the relative abundance of R.solani was lower than that in other crop residue soils.It was concluded that the HQ was a reasonable soil resource to replace the uncultivated meadow soils.In conclusion,the soil characteristics of the previous crops created the different taxonomy,composition,and function of the rhizosphere microbial communities in A.sinensis seedlings.The results and conclusions enriched the understanding of the composition and function of the rhizosphere microbial community in the growth stages of A.sinensis seedlings,and provided a theoretical basis for the soil resource selection of A.sinensis seedlings and for the microbial control strategies during the growth stages. |
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