Valorization of Moroccan Phosphate Sludge Through Isolation and Characterization of Phosphate Solubilizing Bacteria and Assessment of Their Growth Promotion Effect on Phaseolus Vulgaris

Mining activities generate considerable quantities of wastes that are usually accumulated in the open air, and form dykes that disfigure the landscape and arable land. The present study aims to isolate and select the phosphate solubilizing bacteria (PSBs) from Phosphate Solid Sludge to improve the agronomic efficacy of phosphate bio-fertilizers. Thirty-one bacterial strains were isolated from the Moroccan phosphate sludge, from which 24 were retained after molecular phylogenetic analysis of 16S rRNA sequences and characterized biochemically, phenotypically, and genotypically. Strains with the best plant growth-promoting and tolerance to abiotic stress traits were therefore reselected for the biocontrol test against Fusarium oxysporum and Botrytis cinerea and inoculation trials of Phaseolus vulgaris. The 24 selected strains have significantly different abilities to solubilize Moroccan rock phosphate, and the quantity of soluble phosphate varied between 3.25 and 140 µg/ml. Out of 24 selected PSBs, 33