Enterobacter sp. DBA51 produces ACC deaminase and promotes the growth of tomato (Solanum lycopersicum L.) and tobacco (Nicotiana tabacum L.) plants under greenhouse condition

Abstract

Bacterial isolated from rhizospheric soil associated with the semi-desertic plant Coronilla juncea L. were screened for 1-aminocyclopropane-1-carboxylate deaminase (ACCD) activity, a common trait for plant-growth-promoting rhizobacteria (PGPR). Among bacterial isolates, strain DBA51 showed phosphate solubilizing index (PSI), producing indole acetic acid (IAA), and with the hemolysis-negative test. Sequencing and analysis of the 16S rDNA gene identified DBA51 as Enterobacter. DBA51 did not show antagonistic activity in vitro against bacterial (Clavibacter michiganensis, Pseudomonas syringae pv. tomato DC3000 and Pectobacterium cacticidum FHLGJ22) and fungal phytopathogens (Alternaria sp., Fusarium oxysporum fsp. lycopersici, Fusarium oxysporum fsp. cubense M5, and Rhizoctonia sp.). Root inoculations with DBA51 in tomato (Solanum lycopersicum L.) and tobacco (Nicotiana tabacum L.) plants were performed under greenhouse conditions. Plant height (20 %) and root biomass (40 %) were significantly enhanced in tomato plants inoculated with DBA51 compared to non-inoculated plants, although for tobacco plants, only root biomass (27 %) showed significant differences with DBA51. In addition, physiological parameters such as photosynthetic rate (µmol CO₂ m⁻² s^-1), stomatal conductance (mol H₂O m⁻² s⁻¹), and transpiration rate (mmol H₂O m⁻² s⁻¹) were also evaluated, and no differences were detected between DBA51-inoculated and control treatment in tomato and tobacco leaves. The observed results indicate that the DBA51 strain could be used as a biofertilizer to improve yields of horticultural crops.