Isolation and molecular identification of an indigenous abiotic stress-tolerant plant growth-promoting rhizobacteria from the rhizosphere of the olive tree in southern Morocco

Abstract

The current study was conducted to isolate and identify rhizobacteria with PGP properties from the rhizosphere of olive tree groves in southern Morocco. The rhizobacterial isolates were evaluated in vitro for their tolerance to salinity and temperature stress as well as for their PGP activities. From a total of 160 rhizobacterial isolates, 20 were selected for further molecular identification and characterization. Among these, 65% were thermotolerant (≥45 °C) and 80% were halotolerant (≥4% NaCl). IAA production ranged from 0.43 to 181.43 μg/mL and phosphate solubilization oscillated between 3.3 and 166.89 μg/mL. Moreover, 65% of the isolates were able to produce siderophores. Molecular identification based on phylogenetic analysis of 16S rRNA gene revealed that the isolates belong to Enterobacter, Pseudomonas, Acinetobacter, Erwinia, Bacillus, and Arthrobacter genera. Three bacterial strains with prominent multi-trait PGP activities and good tolerance to salinity and elevated temperatures were finally selected and matched to Bacillus licheniformis (MSRC76), Arthrobacter globiformis (MSRC52), and Bacillus megaterium (MSRC23) with 99–100% similarity. Testing of these PRGP strains on the olive tree in pot and field conditions will further elucidate and prove their benefit potential on the plant growth and the tolerance to biotic and abiotic stresses.