Two Isolates From Plants Cultivated in Red Lateritic Soils are Good Candidates for the Development of Microbial Biostimulants.

Abstract

Phosphorus is essential for plant growth, yet its availability in soils is extremely limited, with less than 0.1% accessible to plants. Though phosphate fertilizers are frequently employed to address this deficiency, a significant portion of the applied phosphorus is quickly fixed and unavailable to plants. Thus, the use of plant growth-promoting bacteria (PGPB) capable of solubilizing insoluble phosphate is an increasingly accepted eco-friendly agricultural practice to enhance phosphorus availability. This study aimed to isolate native phosphorus-solubilizing bacteria from lateritic and sandy soils of Misiones and Corrientes provinces (Argentina) and to study their plant growth-promoting attributes. Among the 17 isolates obtained following a selective protocol, two isolates, here named BVP24 and MMBR01, exhibited the highest phosphate solubilization activity (greater than other reported microorganisms) and produced substantial amounts of indole acetic acid. Both isolates were identified as Priestia megaterium via MALDI-TOF analysis and inhibited in vitro Fusarium graminearum growth. MMBR01 additionally inhibited Bipolaris sorokiniana growth. A dose of 1 × 10⁶ CFU per seed was the most efficient to promote root dry weight in maize seedlings. Based on their plant growth-promoting capacities, these native strains emerge as potential biofertilizers, offering an alternative to synthetic phosphate fertilizers and contributing to more sustainable phosphorus management.