Seleção de bactérias diazotróficas não simbióticas solubilizadoras de fosfatos

Abstract

ABSTRACT One of the most important resources of nitrogenn present on the soil are biological fixation process of atmosferic N2, as nitrogen the phosphorus has a importante role on biosphere, since he is part of nucleic acids that stock de genetic code. A lot of photosynthesis and celullar respiration intermediaries substancies are combined with phosphorus, besides, this one is part of the energetic coin of life, the ATP. With this study, the objective was to isolate and select diazotrophics rhizobacteria, not simbiotics that are capable of solubilizating phosphates and evaluate the efficient of interacting with corn (Zea mays .L) seedlings in vitro. 57 strains grew in Nfb and JmV (nitrogen-free) solutions, 11 showed formation of a transparent halo around the colony cultivated on solid solution, indicating the ability to solubilize calcium phosphate (Ca5(PO4)3OH) added to NBRIP. among the eleven isolated bacterias 3 presentes low solubilization with IS ( solubilization indice) ranging between 1,140 to 1,417. One of then reatch medium level ( IS 2,735), and 7 bacterias present hight level of solubilization ( IS ranging between 3.102 to 12,750). 8 of these isolated colonized all the radicular system and the region of the lap , one colonized just a part (DBSF47), and two colonized just the region of the lap (DBSF40 and DBSF58). The analyzes of variance detected a significance (test F p<0,05) for the parameters: plant height (PH), root length (RL), stalk diameter (SD), foliar area (FA), number of leafs (NL) and total weitgh of dry matter (TWDM) .PH, only the isolated DBSF40, do not differed significantly of control, while the oders promote a significant increase with emphasis on DBSF21 (16.970 cm) e DBSF33 (16,767 cm), in RL has noted significantly diferences between control and strains, the greatest lenghts were with the strains DBSF30, DBSF37, DBSF40, DBSF47 e DBSF58. For SD the observed results to DBSF30, DBSF37, DBSF42, DBSF47 e DBSF64 do not differed significantly of control. the highest value has been checked was found for the strain DBSF20 which did not show significant differences in relation to DBSF33, DBSF40, DBSF41 e DBSF58. as for the NL only the strain DBSF58 differed from the control with 3 leaves. Regarding FA, all isolates promoted a significant increase compared to the control, with the best results being verified for DBSF58, DBSF40 and DBSF20 (16,763, 15,950 and 15,950 cm2 respectively).In the highest mass production of TWDM by seedlings, all isolates differed statistically (p<0.05) from the control, the average was verified for DBSF40 (1.00g). All isolates selected as diazotrophic showed characteristics to promote plant growth.

Keywords: bacterias, non simbyotic, growth promotion, diazotrophs