Characterization of Multitrait Plant Growth-Promoting Rhizobacteria From Opuntia ficus-indica in Different Moroccan...

Plant growth-promoting rhizobacteria (PGPR) enhance plant fitness through nutrient mobilization, hormone modulation, and improved tolerance to abiotic stresses. Despite the ecological and agricultural importance of Opuntia ficus-indica, a drought-adapted cactus widely cultivated in arid and semiarid regions, little is known about its rhizosphere microbiota. This study aimed to select culturable rhizobacteria associated with O. ficus-indica, assessing their plant growth-promoting (PGP) traits and identifying strains with potential for improving crop performance under challenging environmental conditions. Bacterial strains from the rhizosphere of O. ficus-indica were isolated across three Moroccan regions with distinct rainfall regimes: Tafrant (humid), Fez (semiarid), and Chichaoua (arid). Seventy-seven strains were isolated and screened for their PGP traits, including phosphate solubilization, indole-3-acetic acid, siderophore, ammonia and HCN production, exopolysaccharide synthesis, in vitro nitrogen fixation, and antagonistic activity against Fusarium solani. Twenty-two high-performing isolates displaying superior PGP traits were selected. Molecular identification revealed taxonomic diversity across three bacterial groups: Gammaproteobacteria (Pseudomonas, Acinetobacter, Enterobacter, and Stenotrophomonas), Actinobacteria (Streptomyces, Arthrobacter, Kocuria, and Citricoccus), and Firmicutes (Bacillus, Peribacillus, Virgibacillus, Terribacillus, and Priestia). Isolates from semiarid and arid regions exhibited higher tolerance to drought-mimicking stress. Several isolates enhanced seed germination and seedling growth parameters in wheat, with the highest germination percentage induced by Peribacillus frigotolerans ZFSp2 and Pseudomonas moraviensis ZN17. Sorghum germination rate was highest in the presence of ZFSp2. These results highlight the rhizosphere of O. ficus-indica as a valuable reservoir of PGPR with strong potential for applications in sustainable agriculture, particularly in arid and semiarid regions.