| Soybean has a cultivation history of over 5000 years in China as an important grain and oil crop.The current supply crisis triggered by the huge production and demand gap of soybeans is very prominent,and the import channels are highly concentrated,with a high dependence on a few countries,which has clearly exceeded the usual safety bottom line,and has posed a significant threat to China’s food security.Boosting soybean production capacity has become an important measure to supplement the national food security gap.The increase in soybean production capacity is greatly influenced by agricultural cultivation patterns on the one hand,and the legacy effects generated by farmland ecosystems with different cultivation histories can also affect soybean production capacity by reshaping soil microbial communities and changing soil physical and chemical environments.Therefore,exploring the legacy effects of agricultural management on soybean rhizosphere microbial communities and their interaction with plants is of great significance for rational planning of agricultural production and efforts to improve soybean yield.In this paper,high-throughput sequencing technology and eukaryotic transcriptome analysis technology were used to reveal the impact mechanism of different cultivation modes on soybean rhizosphere microbial community,explore the impact of continuous and rotation cultivation modes on the composition,diversity,and interaction of soybean rhizosphere microbial community,and clarify the impact of legacy effects of different agricultural use historical soils on microbial community composition and assembly process,discovered keystone microorganisms with potential to promote soybean growth,and ultimately synthesized and validated a growth-promoting microbial community with nutrient activation function.The main results are as follows:(1)The results based on high-throughput sequencing analysis showed that the diversity and interaction of soil bacterial and fungal communities had different response mechanisms to rotation and continuous cropping patterns.The diversity of soil bacterial communities under rotation cultivation mode is low,but the network complexity is high,while fungi show the opposite trend.The main environmental factors driving the influence of soil bacterial and fungal communities are soil moisture content and p H.(2)In the pot experiment,the results of co-occurrence network analysis showed that in the historical soil of rotation utilization,the diversity of rhizosphere bacterial communities in soybean during the R3 period of growth and development was significantly higher than that in the historical soil of continuous cropping utilization.For bacterial communities,the diversity of soil microbial communities in the R3 rotation period of soybean growth is significantly higher than that in the continuous cropping period.At the same time,the R3 rotation period has the most stable soil bacterial network,while the V3 rotation period has the most stable soil bacterial network.For fungal communities,the diversity of soil microbial communities during V3 and R3 continuous cropping was significantly higher than that during rotation.At the same time,the soil fungal network during R3 continuous cropping was the most unstable,while the soil fungal network during V3 rotation was the most unstable,opposite to bacterial communities.(3)The results of community assembly process analysis based on neutral model and zero model showed that,for bacterial communities,community assembly in the soil of continuous cropping use gradually changed from a deterministic process to a stochastic process with the growth and development of soybean,while the trend in the soil of rotation use was roughly opposite.For fungal communities,different utilization histories,parts,and soybean development stages are almost entirely dominated by homogenization selection in deterministic processes.(4)Affected by the legacy effects of rotation history,the fresh and dry weight of pods in soil under rotation utilization is significantly higher than that in continuous cultivation soil.The expression levels of genes related to protein activation,catalytic activity,biosynthesis of secondary metabolites,extension of fatty acid chains,nitrogen metabolism,and plant pathogen interaction in historical soil under rotation utilization are much higher than those in continuous cultivation soil.The rhizobiaceae in the core microorganisms obtained from the analysis of continuous cropping soil networks was significantly positively correlated with the phenotype of soybean plants,while the Leptosphaeriaceae was found in the rotation soil.(5)Based on the experiments of pure cultivation and growth promoting characteristics of microorganisms,we isolated a total of 156 bacterial strains from soil samples of field and pot experiments under two cultivation modes of rotation and continuous cropping.Among them,61 strains had the ability to dissolve organic phosphorus,4 strains had the ability to dissolve inorganic phosphorus,and the vast majority had varying degrees of potassium solubilization ability.The synthetic microbial community constructed by the five strongest strains,R4-6,R4-11,C6-6,C1-10,and C1-6,can promote the underground growth of soybean plants and enhance the stability of soybean rhizosphere bacterial network.To sum up,this paper uses mature experimental techniques such as high-throughput sequencing and transcriptome analysis to clarify the impact of different cultivation modes on the composition,diversity,interaction and relationship with environmental factors of soybean rhizosphere flora,and reveals the mechanism of legacy effects brought by different agricultural use of historical soils on the composition and assembly process of soybean rhizosphere flora at different development stages,Clarify the core microbial groups that have the potential to improve soybean plant productivity.Especially,based on large-scale pure cultivation of single microbial strains,a synthetic functional microbial community with promoting soybean root development has been constructed,laying the foundation for the development of microbial agents.The above research results provide theoretical support for formulating reasonable soybean production management measures,exploring ways to increase yield,and providing a new perspective and microbial strain resources for the large-scale development of plant rhizosphere growth promoting microbiota with application value. |
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