Diversity And Plant Growth Promotion Of Endophytic Bacteria Isolated From Oryza Nivara

Plant-promoting bacteria can promote plant growth both directly and indirectly.Plant growth-promoting bacteria on the one hand can synthesize the growth active substances required for plant growth and development,and change the physical and chemical properties of the soil,and directly promote the growth and development of plants through nitrogen fixation,phosphorus solubilization,potassium release,and iron-producing carriers;on the other hand,plant growth promotion Bacteria inhibit the growth of other pathogenic microorganisms by competing for space and nutrient resources and hindering the occurrence of plant diseases,weeds and weeds.In this study,wild rice of Oryza nivara was used as a test material.Endophytic bacteria were isolated and purified using two kinds of nitrogen free medium(DN and NFB).IS-PCR insertion sequence fingerprinting was used to cluster endophyte groups,and 16 S rRNA gene sequence analysis was used to established the phylogenetic relationships of endophytes;Salkowski colorimetric method was used to quantitatively measure the ability of endophytic bacteria to produce auxin.The method of dissolving and transparent rings was utilized to qualitatively detect the ability of dissolving phosphorus and potassium of the strains.The molybdenum-antimony colorimetric method and the atomic absorption spectrophotometer method were used to quantitatively measure the level of the ability of dissolving and dissolving potassium of the strains.CAS method was utilized to detect whether endogenous bacteria produced iron-producing carriers.Finally,the physiological and biochemical characteristics of the strains and their tolerance to cid-base,antibiotics and NacCl were measured.(1)In this study,wild rice of Oryza nivara was used as the experimental material,two kinds of nitrogen free medium(DN and NFB)were used to separate and purify the endophytic bacteria,and 113 endophytic bacteria were obtained.21 strains were obtained by the method of IS-PCR insert sequence fingerprint clustering.The phylogenetic relationships of endophytes were determined by the 16 S rRNA gene sequences of representative strains of diverse groups.The isolated endophytes were Bacillus siamensis,Bacillus tequilensis,Klebsiella singaporensis,Klebsiella quasipneumoniae subsp.quasipneumoniae,Burkholderia contaminans,Ochrobactrum haematophilum,Klebsiella michiganensis.Burkholderia vietnamiensis,Enterobacter ludwigii,Citrobacter bitternis,Pseudomonas beteli,Ralstonia pickettii,Herbaspirillum seropedicae,Raoultella ornithinolytica,Enterobacter cloacae subsp.dissolvens,Patullibacter americanus,Humicacter aquilariae,Achromobacter insuavis,Achromobacter xylosoxidans,Bacillus toyonensis and Bacillus licheniformis.It indicates that the endophytic bacteria of wild rice in Oryza nivara have rich genetic and species diversity.(2)Through the determination of the growth promoting ability of 113 the endogenous bacteria of wild rice Oryza nivara,97 strains were obtained and the production of auxin was distributed between 1.28 and 34.97 mg/L.Among them,10 strains produced prominence,including kq1,kq3,oh3,km1,en2,en3,cs3,hs1,ro6,and bt2.Corresponding auxin levels were 31.25 mg/L,32.46 mg/L,,32.27 mg/L,30.06 mg/L,31.06 mg/L,32.36 mg/L,32.78 mg/L,34.97 mg/L,35.25 mg/L and 44.96 mg/L,respectively.Ninety strains with nitrogenase activity were screened and their nitrogenase activity was measured between7.85 and 618.13 nmol/(mL?h)by the acetylene reduction method.Among them,seven strains with high nitrogenase activity were oh3.,bv1,cs3,cs4,hs1,ro2 and ro6,measured the corresponding nitrogenase activity was 618.13 nmol/(mL?h),571.28 nmol/(mL?h),387.61 nmol/(mL?h),373.01 nmol/(mL?h),403.16 nmol/(mL?h),362.17 nmol/(mL?h)and463.24 nmol/(mL?h).Sixty-four endophytic bacteria with P-solubilizing effect were screened.P-dissolving ability was distributed between 5.79 and 73.81 mg/L.Phosphorus-dissolving effect of 10 endophytic bacteria was good.They were ks3,ks5,oh3,bv1,cs3,cs4,rp2,ro1,ro6 and ec1.The content of soluble phosphorus in the corresponding fermentation broth was 40.22 mg/L,46.42 mg/L,56.72 mg/L,55.34 mg/L,67.8 mg /L,43.01 mg/L,51.78 mg/L,43.55 mg/L,73.81 mg/L and 43.29 mg/L,respectively.Sixty-five strains with potassium-releasing effect were obtained.Potassium releasing capacity was distributed between 2.29 and 97.24 mg/L,of which 8 dominant strains were oh3,bv1,cs1,cs3,hs1,hs2,ro1,and ro6.The content of soluble potassium in the corresponding fermentation broth was measured to be 97.2 mg/L,86.43 mg/L,50.31 mg/L,88.52 mg/L,72.27 mg/L,56.27 mg/L,53.04 mg/L,and 80.04 mg/L respectively.102 strains of endophytic strains which could produce iron carrier were screened,and the color of the siderophores was purple,red and pink.The above experimental data show that the endogenous bacteria of wild rice Oryza nivara have rich functional diversity.(3)Through a comprehensive evaluation and analysis of experimental data,4 strains with high growth-promoting ability were obtained,namely oh3,ro6,bv1 and cs3.After the dominant strain was inoculated with lettuce,the plant height of lettuce increasedsignificantly by 38.14% to 87.51%,the leaf length of lettuce increased significantly by77.01% to 128.00%,the fresh weight of lettuce increased significantly by 52.08% to128.66%,and the dry weight of lettuce increased significantly by 97.48% to 275.58%,the underground root weight of lettuce increased significantly by 14.96% to 73.32%.These indicate that the prevailing strains can provide potential microbial resources for the production of microbial fertilizers.