Rock Powder Solubilization and Growth Promotion of Passiflora edulis Seedlings by Bradyrhizobium viridifuturi

Abstract

The utilization of plant growth-promoting microorganisms (PGPMs) represents a promising and environmentally sustainable approach to enhance global food production. These microorganisms improve nutrient availability by solubilizing minerals such as phosphates and silicates, especially when used in combination with organic fertilizers, thereby stimulating plant development. This study aimed to evaluate the rock powder solubilization capacity of PGPMs in vitro and their agronomic efficiency when combined with organic fertilizers on the growth of Passiflora edulis seedlings. Four bacterial strains Bradyrhizobium viridifuturi , Achromobacter spanius and Bacillus cereus . were characterized based on genetic, biochemical, and physiological traits, including hydrolytic enzyme production and their ability to solubilize rock powder. Parameters influencing solubilization, such as pH and electrical conductivity, were also evaluated. Greenhouse experiments were conducted over 60 and 90 days to assess seedling growth under four substrate conditions, with and without chemical fertilization. Growth parameters, including plant height, stem diameter, leaf number, and nutrient accumulation, were measured. (A) spanius and (B) cereus , effectively solubilized silicate rock in vitro. Notably, B. viridifuturi significantly enhanced seedling growth and nutrient uptake when applied to substrates containing both organic fertilizer and rock powder. These findings underscore the potential of PGPMs particularly B. viridifuturi as sustainable bioinoculants to improve nutrient availability and optimize seedling development in agricultural systems.

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