Phosphate Rock Solubilization by Burkholderia and Paraburkholderia Strains: Implications for Biofertilizer Development in Sustainable Agriculture

Phosphorus is a vital nutrient for plant development, yet its availability in soil is often limited by fixation in insoluble compounds. While abundant, phosphate rock (PR) exhibits low solubility, which reduces its agronomic value. The use of phosphate‐solubilizing microorganisms offers an eco‐friendly alternative for enhancing phosphorus bioavailability in agriculture. This study aimed to evaluate six bacterial strains from the Burkholderia and Paraburkholderia genera for their ability to solubilize phosphorus from PR using two selective media: Pikovskaya (PVK) and National Botanical Research Institute’s Phosphate. Solubilization was assessed via halo formation on solid media and quantification of soluble phosphorus in PVK and PVK + PR liquid cultures, and we quantified indole‐3‐acetic‐acid. A three‐way ANOVA indicated that bacterial strain and evaluation time significantly affected halo diameter, but not the type of medium. In PVK + PR liquid medium, B. anthina (10 PEI) and B. gladioli (FB‐1Ma3) showed the highest phosphorus solubilization (31.6 ± 0.2 and 26.3 ± 0.2 mg L −1 , respectively; n = 3), whereas B. contaminans (MSR2) exhibited the lowest (6.44 ± 0.7 mg L −1 ). Indole‐3‐acetic acid production ranged from 4.1 ± 0.9 to 10.6 ± 1.4 μg mL −1 , with P. rhynchosiae (SCV21) and P. graminis (SCV16) yielding the highest values. Notably, B. gladioli did not form halos in solid media despite strong PR solubilization in liquid culture, underscoring the limits of halo‐based screening. These results highlight strain‐dependent solubilization of PR and the complementary value of liquid assays. Selected Burkholderia sensu lato strains, together with their indole‐3‐acetic acid production, are promising candidates for biofertilizer development in phosphorus‐deficient systems, provided biosafety is carefully assessed.