Mechanism Of Microbiome In Regulation Of The Adaptability Of Iron Deficiency In Soybean &maize Intercropping System

The Loess Plateau area is an alkaline calcareous soil,and the solubility of iron in the soil is severely reduced due to high p H and high content of carbonate,which significantly inhibits the absorption and utilization of iron by crops.Plant intercropping can complement resources between crops and play an important role in improving system productivity,promoting soil nutrient activation and crop absorption and utilization,and changing soil microbial community structure.However,little known about how intercropping affects iron uptake and utilization in soil-plant systems and the underlying principles of microbiology.Therefore,in this study,soybean and maize plants were used as experimental materials,soil was collected from the field for pot experiments,and various methods of physiology and biochemistry,highthroughput sequencing and metabolomics were used to study iron absorption,and transport,and response mechanisms to effects and differences in root-associated microbial diversity and root exudates in soil-plant systems under soybean/maize intercropping.This study can provide theoretical basis and scientific basis for the regulation of plants under different iron content conditions in soil,and provide new ideas and solutions for alleviating iron deficiency in plants.In addition,it provides a scientific basis for activating and promoting the efficient utilization of iron in alkaline calcareous soils in northern semi-arid regions and improving crop productivity.These are our main research results:(1)Both iron deficiency and iron excess inhibited the growth of soybean and maize.The dry weight of different compartments of the plant in the three periods was the highest when the iron content was appropriate,and intercropping significantly increased the dry weight of soybean leaves;The chlorophyll content and photosynthetic rate of soybean and maize increased gradually;and intercropping significantly increased the photosynthetic rate of maize.Intercropping improves the absorption and utilization of iron and other nutrients in plants.Compared with monocultures,intercropping significantly increased the content of iron,organic carbon and total phosphorus in soybean and the content of total nitrogen,organic carbon and total phosphorus in maize;and the soil total nitrogen,organic carbon and β-glucosidase contents were increased in three periods of soybean and maize.(2)Different iron concentrations and planting patterns affected the diversity of microbial communities.In root zone,rhizosphere and endophyte of soybean,and root zone and rhizosphere of maize,the microbial communities of different planting patterns and iron contents were significantly different.Different iron concentrations and planting patterns changed the microbial communication associated with plant roots.Under iron deficiency conditions,the soybean rhizosphere was significantly enriched with Herpetosiphon,Ensifer,and Gaiella,and the maize rhizosphere was significantly enriched with Microbacterium and Rhizobium,which are potential strains with the ability to produce siderophores or to promote plant iron absorption.Planting patterns and iron content also altered the interaction relationships of the microbial communities.At low deficiency,microbial networks in intercropping system is more complex than it in monoculture system in soybean and maize rhizosphere.(3)Intercropping significantly changed the structure and composition of soybean and maize root exudates,and had a greater impact on soybean root exudates;while iron content only had a significant effect on maize root exudates.Under the condition of iron deficiency,Oleamide,Fenpropimorph,Coumestrol and other substances were significantly enriched in soybean roots during intercropping,and Oleamide,Coumestrol,Daidzein and other substances were significantly enriched in maize roots during intercropping.(4)Soil physicochemical properties affect the structure and composition of microbial communities and root exudates,root exudates were correlated with microbial communities,and the correlation was stronger in maize.In maize rhizosphere,Coumestrol was significantly positively correlated with Nakamurella;in soybean rhizosphere,Coumestrol was significantly positively correlated with Pirellula,which may potentially have the effect of promoting plant iron absorption.Root exudates associated with microorganisms significantly enriched in intercropping systems under iron deficiency conditions,and microorganisms significantly associated with Coumestrol potentially have the capacity to promote plant iron uptake.In summary,soybean/maize intercropping improved the adaptability of plants to irondeficient environments in alkaline calcareous soil,thereby promoting the absorption of other nutrients in plants,and improving the total nitrogen,organic carbon and other nutrients in the soil.Under iron-deficient conditions,the soybean and maize rhizospheres were significantly enriched with relevant microorganisms and root exudates,which may have the ability to generate siderophores or promote iron uptake in plants.This study provides potential microbial resources for improving iron uptake by crops in iron-limited soils,and provides a theoretical basis for diversifying planting to improve crop productivity.