Culturable diazotrophic bacterial community associated with Agave sisalana P. plants from semi-arid regions in Brazil

Abstract

The aim of this study was to isolate, quantify, identify and characterize the culturable diazotrophic bacterial community associated with sisal (Agave sisalana P.) and assess its potential for plant growth promotion and tolerance to abiotic stress. Nitrogen-free Burk’s medium was used for bacteria isolation and quantification. Isolates carrying the nifH gene were typed by BOX-PCR and sequenced for the 16S rRNA region. Additionally, the bacteria was tested for growth promotion in maize plants and for salinity tolerance in cucumber seedlings. The representative isolates were identified as members of Pantoea, Rhizobium, Burkholderia, Leifsonia and Bacillus genera. All isolates were positive for at least two of the nine plant growth promoting (PGP) traits tested. All isolates showed positive traits for tolerance to abiotic stress. Leifsonia sp. (S1.5) significantly increased root length, stem length and total fresh matter, and it was involved in the reduction of deleterious salt effects (60 mM NaCl) in cucumber seedlings. Diazotrophic bacterial community associated with sisal plants is genetically diverse, exhibits several plant growth-promoting traits and shows potential to support plant growth in adverse environments (salinity).