First report of phosphate-solubilizing bacteria associated with Agave angustifolia

In this study, we isolated, characterized, and evaluated the tricalcium phosphate solubilization ability of phosphate-solubilizing bacteria (PSB) from the rhizosphere of maguey espadín (Agave angustifolia Haw.) plants cropped in mountain, hill and valley soils in Oaxaca, Mexico. Strains with the greatest phosphate-solubilizing capacity were identified biochemically using the API 20 NE and API 20 E kits (bioMerieux, USA). Forty-four PSB strains were isolated, and 24 were selected based on their phosphate solubilization efficiency and solubilization indices. Of these 24, nine (PSBVa, PSBVb, PSBVf, PSBHa, PSBHc, PSBHd, PSBMg, PSBMh and PSBMi) were selected as the most efficient phosphate solubilizers based on criteria including the amounts of solubilized phosphorus in culture filtrate and organic acids produced and the culture filtrate pH change. The highest PSB population was found in mountain soils. All selected strains were able to produce indole-3-acetic acid and gibberellic acid. Biochemical and morphological tests revealed genetic diversity among the strains studied. PSBVb, PSBMg, and PSBMh were identified as Pseudomonas luteola; PSBHc and PSBHd as Burkholderia cepacia; PSBVa as Enterobacter spp.; PSBVf as Burkholderia gladioli; PSBHa as Sphingomonas paucimobilis; and PSBMi as Aeromonas hydrophila. These PSB could serve as potential biofertilizers to improve the phosphorus nutrition of maguey espadín plants as has been demonstrated in previous studies.