Abstract

GUZMAN, Andrés; OBANDO, Melissa; RIVERA, Diego  and  BONILLA, Ruth. Selection and characterization of plant growth promoting rhizobacteria (PGPR’s) associated with cotton crop (Gossypium hirsutum). Rev. colomb. biotecnol [online]. 2012, vol.14, n.1, pp.182-190. ISSN 0123-3475.

As part of strategies for sustainable agriculture, it is necessary to reduce the use of synthetic nitrogen fertilisers through the use of biofertilisers. In particular, the genera Azotobacter and Azospirillum are used as plant growth promoters because of their ability to fix atmospheric nitrogen and indolic type hormones. For this reason, in this study were isolated diazotrophic bacteria of the genera Azotobacter and Azospirillum from the rhizosphere of cotton crops in Espinal (Tolima). The microbial populations were characterized phenotypically in specific semi culture media: Ashby and LG (Azotobacter sp.) and NFb, LGI and Batata (Azospirillum sp.). The promotion of plant growth was determined by the enzyme nitrogenase activity through acetylene reduction technique and production of indoles by the salkowsky colorimetric method. 9 isolates were obtained tentative Azotobacter sp. and 4 of Azospirillum sp. Significant differences in acetylene reduction test with presumptive strains of Azotobacter sp.: NAT 9 (206.43 nmol C₂H₂ mL^-1.h^-1), NAT, 4, (292.77 nmol C₂H₂ mL^-1.h^-1), and NAT 6 (460.60 nmol C₂H₂ mL^-1.h^-1) and indole production strains NAT 19 (19.87 µg.mL^-1) and NAT 13 (20.08 µg.mL^-1). In vitro efficiency in promoting plant growth were selected strains NAT9, NAT4, NAT6, NAT19 and NAT13 to be evaluated as active in future inoculants on cotton in this part of the department of Tolima.

Keywords : biological nitrogen fixation; indole production; plant growth-promoting; biofertilisers.

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