Actinobacteria from Extreme Niches in Morocco and Their Plant Growth-Promoting Potentials

The objectives of this study were to assess actinobacterial diversity in five Moroccan extreme habitats and to evaluate their plant growth-promoting (PGP) activities. The soil samples were collected from different locations, including soils contaminated with heavy metals, from a high altitude site, from the desert, and from a marine environment. In total, 23 actinobacteria were isolated, 8 from Merzouga sand soil; 5 from <i>Cannabis sativa</i> rhizospheric soil; 5 from Toubkal mountain; 4 from a Draa sfar mining site; and 1 from marine soil. Based on their genotypic classification using 16S rRNA gene sequences, 19 of all belonged to the genus <i>Streptomyces</i> (82%) while the rest are the members of the genera <i>Nocardioides</i> (4.5%), <i>Saccharomonospora</i> (4.5%), <i>Actinomadura</i> (4.5%), and <i>Prauserella</i> (4.5%). Isolates <i>Streptomyces</i> sp. TNC-1 and <i>Streptomyces</i> sp. MNC-1 showed the highest level of phosphorus solubilization activity with 12.39 and 8.56 mg/mL, respectively. All 23 isolates were able to solubilize potassium, and 91% of them could grow under nitrogen-free conditions. The ability of the isolated actinobacteria to form indole-3-acetic acid (IAA) ranged from 6.70 to 75.54 &#956;g/mL with <i>Streptomyces</i> sp. MNC-1 being the best IAA producer. In addition, all of the actinobacteria could produce siderophores, with <i>Saccharomonospora</i> sp. LNS-1 synthesizing the greatest amount (138.92 &#956;g/mL). Principal coordinate analysis revealed that <i>Streptomyces</i> spp. MNC-1, MNT-1, MNB-2, and KNC-5; <i>Saccharomonospora</i> sp. LNS-1; and <i>Nocardioides</i> sp. KNC-3 each showed a variety of high-level plant growth-promoting activities. The extreme environments in Morocco are rich with bioactive actinobacteria that possess a variety of plant growth-promoting potentials that can further benefit green and sustainable agriculture.

Abstract licence: CC BY

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