Plant growth-promoting rhizobacteria

by | Apr 10, 2024 | South Africa Wine Scan

Grape production in the Sao Francisco Valley in Brazil requires large amounts of fertiliser input, fuelling cost inflation for producers. Researchers prospected six sites for plant growth-promoting rhizobacteria to identify beneficial species, promote further research and possibly reduce fertiliser inputs.


Project Layout

Rhizospheric soil samples were collected from six sites in the Sao Francisco Valley. Bacterial isolates were produced and evaluated regarding their phenotypic characteristics, phosphate solubilisation, nitrogen fixation, IAA (auxin) synthesis, biofilm formation, and antibiosis. The DNA of isolates proven to have favourable plant growth-promoting results were extracted and sequenced for identification.



  • A total of 423 bacteria were identified, of which 99 presented positive results for at least one of the plant growth-promoting factors evaluated.
  • 85% of bacteria solubilised phosphates, 0.74% of bacteria fixed nitrogen, 5.7% synthesised IAA, 11.27% produced biofilm, and 4.01% promoted antibiosis against Xanthomonas campestris pv. Viticola (which causes a significant grapevine disease in Brazil).
  • Stenotrophomanas, Bacillus, Pseudomonas, and Clostridium isolates presented the best results regarding plant growth-promoting mechanism expression, and future research was proposed to better understand their potential.


Significance of the study

These results prove that promoting microbial activity in soils is worthwhile and should be considered when defining whether the soil is healthy. More work needs to be done on regenerative farming practices and how they benefit the soil microbiome and plant growth.



Mendes Júnior, J.P., Fracetto, G.G.M., Fracetto, F.J.C., Silva, D.J., Lira Junior, M. de A. & Barros, F.M. do R. 2024. Prospecting plant growth-promoting rhizobacteria in grapevines in the São Francisco Valley. Revista Caatinga. 37:e11523. DOI: 10.1590/1983-21252024v3711523rc.


Image: Courtesy of Pacific Northwest National Laboratory