Root exudate-derived compounds stimulate the phosphorus solubilizing ability of bacteria

Area of Science:

• Agricultural Science
• Microbiology
• Soil Science

Background:

• Low phosphorus (P) availability in soils is a significant constraint on global food production.
• Most soil P is locked in unavailable forms, limiting plant uptake and crop yields.
• Effective strategies to enhance phosphorus use efficiency (PUE) in crops are urgently needed.

Purpose of the Study:

• To investigate the role of root exudate compounds (galactinol, threonine, 4-hydroxybutyric acid) in stimulating P-solubilizing bacteria.
• To assess the impact of these compounds on bacterial P-solubilization from inorganic and organic sources.
• To evaluate the effect of threonine application on crop growth and soil nutrient availability.

Main Methods:

• Incubation of P-solubilizing bacteria (Enterobacter cloacae, Pseudomonas pseudoalcaligenes, Bacillus thuringiensis) with root exudates and insoluble P sources (calcium phosphate, phytin).
• Measurement of bacterial growth rates and P-solubilization activity.
• Field application of threonine to corn, assessing root growth, plant nutrient content, and soil nutrient levels.

Main Results:

• Individual root exudates did not significantly enhance bacterial growth rates.
• Root exudates, particularly threonine and 4-hydroxybutyric acid, enhanced bacterial P-solubilizing activity and overall P availability.
• Threonine application to soil improved corn root growth, increased root N and P concentrations, and enhanced soil K, Ca, and Mg availability.

Conclusions:

• Root exudate compounds can stimulate bacterial P-solubilization, increasing phosphorus availability.
• Threonine shows potential as a biostimulant to improve nutrient uptake and crop productivity.
• These findings offer novel strategies for unlocking soil phosphorus reservoirs and enhancing crop nutrition.