03217nam a2200325 a 450000100080000000500110000800800410001910000200006024501140008026000510019430000100024550000230025552023650027865000230264365000160266665000090268265000130269165000140270465000240271865000160274265000290275865000100278765000160279765000160281365000140282965000090284365000090285265300110286165300190287215584571998-10-15       1998    bl uuuu  m   00u1 u    #d1 aCATTELAN, A. J.  aScreening and characterization of soil and rhizosphere bacteria for traits that promote early soybean growth.  aAthens, Georgia: Universidade of Georgiac1998  a89 f.  aPhD. Dissertation.  aUnderstanding specifically how a particular species of bacteria is favored for growth in soybean rhizosphere will facilitate e better understanding of root colonization and competitiveness of rhizosphere organisms. This is crucial for the sucess of plant growth promoting rhizobacteria (PGPR) inoculation. We used fatty acid methyl ester (FAME) analysis to identify bacteria in two different soils and in the rhizosphere of nodulating and mon-nodulating (Glycine max (L.) Merr.) cv. 'Lee'. In a lightroom experiment, bacterial isolates from each soil and soybean rhizosphere were selected at 3, 6, and 15 days after planting. Of 1131 bacterial isolates examined, 572 (50.6%) were identified. The majority of the identified isolates were Bacillus (324 isolates), Pseudomonas (121 isolates), and Arthrobacter (48 isolates). Numbers of Bacillus spp. were lower in the rhizosphere of nodulating and non-nodulating soybean compared to root-free soil, and these lower numbers were usually offset by higher numbers of Gram-negative bacteria, especially Pseudomonas spp. From the 1131 isolates, 116 isolates were screened in vitro for a variety of PGPR traits which might increase early soybean growth. A subsample of 23 isolates, all but one of which was positive for one or more of these PGPR traits, was tested in soybean cv. 'Lee' grown in nonsterile soil. Six of eight isolates positive for 1-aminocyclopropane-1-carboxylate (ACC) deaminase production, four of sevem isolates positive for siderophore production, three of four isolates positive for B-1,3-glucanase production, and two of five isolates positive for P solubilization increased at least one aspect early soybean growth. One isolate, wich did not share any of PGPR traits tested in vitro except antagonism to S. rolfisii and S. sclerotiorum, also increased early soybean growth. All isolates that increased soybean growth, seven in total, were Pseudomonads spp. or Pseudomonas-like. One of 23 isolates increased nodule occupancy with strains of Bradyrhizobium elkanii USDA 31. Although the presence of a PGPR trait in vitro does not guarantee that a particular isolate is a PGPR, the results suggest that rhizobacteria able to produce ACC deaminase and, to a lesser extent, produce B-1,3 glucanase or siderophores or able to solubilize P in vitro, may increase early soybean growth in nosterile soil.  abiological control  arhizosphere  asoil  asoybeans  aBactéria  aControle Biológico  aCrescimento  aFixação de Nitrogênio  aFungo  aGlycine Max  aNodulação  aRizosfera  aSoja  aSolo  aGrowth  aRhizobacterias