The Screeing Of Selenium-resistant Strains In Soil And Selenium-rich Effect Mechanism Of Pakchoi On Iatosolic Red Soil

Selenium is a trace element closely related to human health.Guangxi is a typical selenium-rich soil province.However,although selenium-rich soil may have the potential to produce selenium-rich agricultural products,it does not necessarily produce the selenium-rich agricultural products.Therefore,how to improve the biological effectiveness of soil selenium is one of the current research hotspots of current.This experiment uses the diluted coating plate method and flat dash method to separate and screen out microorganisms that can tolerate higher concentrations of sodium selenium from the soil in Enshi,Hubei province,China.And identifies selenium-resistant strains by morphological characteristics and molecular biology methods.The pot and soil culture experiments were conducted to discuss the effect and mechanism of selenium-resistant bacteria B-1 and selenium-resistant fungus B-2 on selenium absorption of pakchoi in acid selenium-rich lateritic red soil.To provide biospecies resources and technical means for the exploitation and utilization of selenium-rich soil resources.Simultaneously,this studyt in selenium-rich microbial fertilizer research and development,selenium-rich agricultural production and selenium-contaminated environment repair and other aspects provide relevant theoretical basis.The main results were as follows:（1）Two high selenium-resistant microorganisms were screened from the selenium-rich soil in Enshi,Hubei Province.Selenium-resistant bacteria B-1was identified as Stenotrophomonas maltophilia,which has a concentration of17000μg·m L^-1.The strain B-1 can grow normally when the temperature was20～35℃,the p H was 5～9,and the Na Cl mass fraction was 0～3%.Selenium-resistant fungus B-2 was identified as Aspergillus sydowii,which has a concentration of 6000μg·m L^-1.The strain B-2 can grow normally when the temperature was 25～30℃,the p H was 4～7,and the Na Cl mass fractin was2～5%.（2）After inoculation of selenium-resistant strains B-1 and B-2,the root length,plant height,ground dry weight,and underground dry weight of pakchoi have increased to varying degrees.Compared with the non-inoculated strains,selenium-resistant bacteria significantly increased the selenium content of the upper part of the pakchoi,with a growth rate of 33.44%to 57.61%.Inoculation of selenium-resistant fungi was better than that of selenium-resistant bacteria,with a growth rate of 37.26%to 61.15%.（3）Screening for selenium-resistant strains B-1 and B-2 can increase the amount of active state selenium in the soil.After inoculation of selenium-resistant strains,the content of soluble selenium,exchangeable selenium,and ferromanganese oxide binding selenium in soil increased,the content of organic binding selenium and residual selenium decreased.It is shown that inoculation of selenium-resistant strains B-1 and B-2 can promote the conversion of different forms of selenium in soil.（4）After inoculation of selenium-resistant strains,the microbiality and species richness of soil bacteria and fungi increased.Moreover,the soil bacterial species richness increased significantly.In addition,inoculation of selenium-resistant strains affected the relative abundance of bacteria and fungal communities.In the soil bacterial community the abundance of Chloroflexi and Gemmatimonadota is relatively increased,but the abundance of Proteobacteria and Acidobacteriota is relatively decreased.The relative abundance of Ascomycota has increased in fungal communities.Through the analysis of results by high-throughput sequencing,the Bacillaceae and Streptomycetaceae in the bacteria and the Chaetomiaceae in the fungus may be the key flora to promote the growth of pakchoi.In summary,inoculation of selenium-resistant strains B-1 and B-2 can significantly improve the effective state selenium content in the soil,and promote the activation of selenium in the soil.At the same time,it improves the microbial biodiversity and species abundance of soil bacteria and fungi,increases the abundance of beneficial flora,and improves the structure of the soil microbiome.Thus promoting the absorption and utilization of the selenium in the soil,and improving selenium content of the pakchoi on the ground.