The decrease in the population of Gluconacetobacter diazotrophicus in sugarcane after nitrogen fertilization is...

Area of Science:

• Agricultural Microbiology
• Plant-Bacterial Interactions
• Nitrogen Metabolism

Background:

• Gluconacetobacter diazotrophicus is a beneficial bacterium associated with sugarcane.
• Nitrogen fertilization is known to decrease G. diazotrophicus populations.
• The mechanism behind this population decrease is not fully understood.

Purpose of the Study:

• To investigate the direct effect of ammonium nitrate (NH4NO3) on G. diazotrophicus survival.
• To determine if high nitrogen levels induce systemic changes in sugarcane affecting bacterial populations.

Main Methods:

• In vitro experiments assessing G. diazotrophicus survival with varying NH4NO3 concentrations.
• Split-root system experiments with micropropagated sugarcane plantlets inoculated with G. diazotrophicus.
• Differential fertilization of split-root systems with basal and high NH4NO3 doses.

Main Results:

• In vitro, high NH4NO3 concentrations (44.8mM) directly inhibited G. diazotrophicus survival.
• In planta, a lower NH4NO3 dose (6.3mM) significantly reduced G. diazotrophicus populations compared to controls.
• Bacterial population decline was more pronounced in basal nitrogen fertilized areas when the other side received high nitrogen.

Conclusions:

• High nitrogen fertilization in sugarcane induces systemic physiological changes that negatively impact G. diazotrophicus establishment.
• The observed decrease in bacterial populations is primarily mediated by plant responses to nitrogen, not solely direct toxicity.