Screening Of Plant Growth Promoting And Salt Tolerant Bacteria From Three Desert Halophytes

The poor physical and chemical properties of saline-alkali soil make it difficult for most plants to survive,which has become one of the biggest limiting factors of crop production.However,plant germplasm with strong stress resistance has been developed in this kind of habitats,which has become the dominant vegetation in different salinealkali areas because of its strong saline-alkali tolerance.Compared with a series of environmental problems caused by long-term application of chemical fertilizer,people pay more and more attention to the development of growth-promoting bacteria in salttolerant plants to improve soil fertility and ecological environment,and to improve crop yield and quality.Based on this,plant growth-promoting bacteria were screened from xerophytic Reed Phragmites communis,Halostachys caspica and Halocnemum strobilaceum of three halophytes in Kirgiz Autonomous Prefecture of Kizilsu Autonomous Prefecture of Xinjiang,and their taxonomic status was confirmed based on restriction endonuclease fragment length polymorphism(PCR-restriction fragment length polymorphism,PCR-RFLP)of 16 S r RNA gene and phylogenetic analysis.The strains with strong growth-promoting ability were selected to analyze their salt tolerance and to explore their effects on plant seed germination and seedling growth under saline-alkali stress.The main results are as follows:(1)A total of 240 PGPB strains were isolated from the three halophytes,among which 100,128 and 76 strains of inorganic phosphorus,organophosphate and nitrogen fixation were respectively.Based on this method,48 ACC deaminase producing strains(1-aminocyclopropane-1-carboxylicacid deaminase),162 iron carrier producing strains,and 181 inole-3-acetic acid(IAA)producing strains were isolated.Their capacities ranged from 0.61±0.03 to 30.33±1.15 μg/m L,1.67±0.15 to 233.61±1.01 μg/m L,14.29±0.29 to 34.00±0.13,respectively IU/L,0.094±0.016 to 0.381±0.016,0.03±0.01 to 5.97±1.23 U/mg,9.70±1.48 to 38.90±3.56 mg/L,the content of dissolved inorganic phosphorus was significantly negatively correlated with the p H value of fermentation solution(P< 0.05).Among all PGPBS,63.75% had more than two growth-promoting functions,35.83% had more than three functions,10% had more than four functions,and 2.5% had six functions.(2)Phylogenetic analysis showed that all PGPB strains belonged to 11 genera,and Enterobacter was the dominant genus,accounting for 66.4% of the total strains.Escherichia followed.Other bacteria genera such as Paenibacillus,Acinetobacter,Psychrobacter and so on were relatively small.All the PGPB strains with different functions had good salt tolerance,and the suitable growth salt concentration range was2.5% to 7%,and the maximum tolerance was 15%.(3)The germination potential,germination rate,root length,bud length and fresh weight of wheat seeds were promoted by inoculating growth-promoting strains with different functions.Compared with the control,they increased 3.09% ～ 27.74%,4.76%～ 22.86%,6.81% ～ 58.97%,1.81% ～ 36.34%,14.69% ～ 50.76%,respectively.(4)The biomass(plant height,stem diameter,above-ground dry weight,root dry weight and chlorophyll content)of wheat seedlings under different salt stress(150mmol/L,200 mmol/L and 300 mmol/L)was positively affected by different functional growth promoters.However,with the increase of salt concentration,the growth promoting effect of PGPB strain was gradually weakened.Inoculation also affected the physiological characteristics of plants,increasing the activities of catalase(CAT),peroxidase(POD)and superoxide dismutase(SOD),and reducing the accumulation of malondialdehyde(MDA)in seedlings.(5)In pot experiment,inoculation of phosphorus-soluble strains significantly increased the seedling biomass of Arabidopsis thaliana under non-saline-alkali stress,especially Enterobacter sp.MHSC29 and Escherichia sp.MHCB24,respectively.It had positive effects on above-ground part(plant height,stem diameter,above-ground dry weight,chlorophyll content)and underground part(root dry weight)of wheat in saline-alkali soil.The results showed that bacillus Enterobacter sp.MHSC29,Acinetobacter sp.MHCC3 and Enterobacter sp.APCB2 strains were effective against organic phosphorus.