Actinobacteria Isolated from Soils of Arid Saharan Regions Display Simultaneous Antifungal and Plant Growth Promoting Activities.

Application of actinobacteria has grown exponentially in recent years in sustainable agricultural. Most actinobacterial inoculants are tailored to function as either biocontrol agents or biofertilizers. Hence, there is the need to obtain and include multifunctional actinobacterial strains in inocula formulations. In this research, 90 actinobacterial isolates were isolated from rhizospheric and non-rhizospheric soils of Algerian Saharan arid regions and were screened for their activity against the phytopathogenic fungi Alternaria alternata, Aspergillus flavus, Botrytis cinerea, Fusarium oxysporum, and Fusarium solani. Five isolates that inhibited at least three of these fungi were characterized according to morphological, environmental and biochemical parameters, and were preliminarily identified as Streptomyces enissocaesilis A1, Streptomyces olivoverticillatus A5, Streptomyces erumpens A6, Streptomyces cavourensis A8, and Streptomyces microflavus A20. These strains were then screened for plant growth promoting activities. All strains produced siderophores, hydrocyanic acid, ammonia and the auxin indole-3-acetic acid (IAA) and were capable of solubilizing phosphate. The highest producer of siderophores (69.19 percent siderophore units), ammonia (70.56 μg mL) and IAA (148.76 μg mL) was strain A8, A20, and A5, respectively. These findings showed that the five actinobacteria are multipurpose strains with simultaneous antifungal and plant growth promoting activities and have the potential to be used for sustainable agricultural practices, particularly in arid regions.