Screening Of Salt-Alkali Tolerant Strains And Its Effect On Wheat Growth And Soil Environment Under Saline-Alkali Conditions

China is one of the countries with serious soil salinization.In recent decades,the unreasonable use of land resources has become more and more serious,and the area of soil salinization has been expanding.Under the premise of advocating sustainable development nowadays,improving saline-alkali land by microorganisms has gradually become a research hotspot.Based on the idea of using microorganisms to improve saline-alkali soil,an extremely salt-alkali tolerant strain was screened from saline-alkali soil,and the growth-promoting effect of the bacteria was investigated.The salt-alkali removal of Gibbson modified liquid medium under different carbon and nitrogen sources was carried out.The effect and the bacterial agent of the strain was applied to the pot experiment of wheat under saline and alkali conditions.The saline-alkali soil samples collected from Dongying,Shandong province were diluted and spread to modified Gibbson medium with pH 9.0 and salt concentration of100g/L.A total of 18 bacteria strains were obtained.By increasing the salt concentration and pH,an extremely salt-tolerant strain 14 was gotten which could grow at pH 12,and salt concentration 20%.Morphology,physiology-biochemistry character and 16SrDNA sequence of strain 14 were analyzed.The results showed that the strain 14 was identified as Bacillus marmarensis.The results of salt-alkali tolerant strain 14 promoting experiments showed that the strain could produce IAA with a secretion of 3.93 ug/mL.The strain also has the functions of potassium dissolving and protease production,and the protease production ability is optimal at pH 7.0,and the enzyme activity is 41.88 U/mL under this condition.Under the condition of Gibbson modified liquid medium,different carbon and nitrogen sources were selected to study the salt-alkali removal ability of strain 14.The results showed that glucose as a carbon source was more favorable for pH reduction,and the alkali reduction rate was 40.25%.The effects of three kinds of nitrogen sources,such as beef extract,peptone and yeast extract,were not obvious.However,when peptone was used as nitrogen source,strain 14 had the fastest rate of alkali reduction;the effect of Cl~-removal by strain 14 was not obvious when these carbon and nitrogen sources were added.Using the strain 14 to prepare the bacterial agent,the pot experiment was carried out with wheat as the material,and the results showed that at 60 days,compared with saline-alkali soil(CK),biofertilizer treatment(T)could significantly increase the activity of invertase,urease and alkaline phosphatase in saline-alkali soil by 23.2%,40.76%and106.5%,respectively(P<0.05).Catalase showed an increasing trend,with a growth rate of6.1%.It could significantly increase the activity of superoxide dismutase,peroxidase and catalase in wheat roots by 109.6%,17.8%,50%,respectively(P<0.05).The content of malondialdehyde in wheat roots was significantly reduced by 39.8%(P<0.05).Biofertilizer treatment(T)could significantly increase the chlorophyll a,chlorophyll b and total chlorophyll in wheat by 36.4%,20.0%and 31.7%,respectively(P<0.05).It also could significantly increase the biomass of wheat,improved plant height,fresh weight and dry weight by 21.8%,57.9%and 41.7%,respectively(P<0.05).There was no significant difference between the culture medium treatment(CM)and the control check(CK),and the influence of the culture medium factor was excluded,indicating that the bacterial agent improved the saline-alkali soil and promoted the growth of wheat.The above experiments show that Salt-alkali tolerant strain 14 has a certain growth-promoting function.Under the condition of liquid medium,it can reduce the pH of the medium.The pot experiment with the bacterial agent of the strain promoted the growth of wheat to a certain extent,and improved the soil enzyme activity and root enzyme activity of wheat in saline-alkali soil.This experiment provides a new idea for the application of extreme salt-alkali tolerant strains,and also provides a basis for microbial measures to improve saline-alkali soil.