Bioprospecting phosphate-solubilizing bacteria in soils with different fertility levels

Abstract

Phosphate-solubilizing bacteria (PSB) have the ability to release fixed phosphorus (P) that is adsorbed in the soil, converting insoluble phosphate into soluble forms, making it readily available for plant absorption. Occurring naturally in various environments, with soil being the main reservoir, PSB are deemed beneficial and safe for agricultural applications. Their potential lies in isolation, multiplication, and reintroduction to the rhizosphere (through inoculants, biofertilizers, biopesticides, or biostimulants) to stimulate plant growth through direct and/or indirect mechanisms. However, identifying efficient isolates adapted to different crops and cropping systems remains a key challenge. This study aimed to prospect PSB from soils of different locations and select efficient strains with high potential for agricultural use via in vitro assays, as well as to evaluate the effects of inoculation on upland rice seeds. From soil samples collected in a conserved Amazonian biome, a productive Cerrado biome agricultural area, and a degraded with exposed subsoil, located in the Cerrado biome area, 32 P-solubilizing isolates were obtained. Among these, three isolates were selected for their early onset ability to solubilize Ca and/or Fe phosphates, and for further analysis. Identified as Pantoea sp., Enterobacter sp., and Klebsiella sp., these isolates proved to be non-harmful to rice seed health, germination, and seedling emergence, additionally promoting increased root length.