*Article* **Rhizospheric** *Actinomycetes* **Revealed Antifungal and Plant-Growth-Promoting Activities under Controlled Environment**

**Hazem S. Elshafie and Ippolito Camele \***

School of Agricultural, Forestry, Food and Environmental Sciences, University of Basilicata, Viale dell'Ateneo Lucano 10, 85100 Potenza, Italy; hazem.elshafie@unibas.it

**\*** Correspondence: ippolito.camele@unibas.it; Tel.: +39-0971205544; Fax: +39-0971205503

**Abstract:** *Actinomycetes* has large habitats and can be isolated from terrestrial soil, rhizospheres of plant roots, and marine sediments. *Actinomycetes* produce several bioactive secondary metabolites with antibacterial, antifungal, and antiviral properties. In this study, some *Actinomycetes* strains were isolated from the rhizosphere zone of four different plant species: rosemary, acacia, strawberry, and olive. The antagonistic activity of all isolates was screened in vitro against *Escherichia coli* and *Bacillus megaterium*. Isolates with the strongest bioactivity potential were selected and molecularly identified as *Streptomyces* sp., *Streptomyces atratus*, and *Arthrobacter humicola*. The growth-promoting activity of the selected *Actinomycetes* isolates was in vivo evaluated on tomato plants and for disease control against *Sclerotinia sclerotiorum*. The results demonstrated that all bacterized plants with the studied *Actinomycetes* isolates were able to promote the tomato seedlings' growth, showing high values of ecophysiological parameters. In particular, the bacterized seedlings with *Streptomyces* sp. and *A. humicola* showed low disease incidence of *S. sclerotiorum* infection (0.3% and 0.2%, respectively), whereas those bacterized with *S. atratus* showed a moderate disease incidence (7.6%) compared with the positive control (36.8%). In addition, the ability of the studied *Actinomycetes* to produce extracellular hydrolytic enzymes was verified. The results showed that *A. humicola* was able to produce chitinase, glucanase, and protease, whereas *Streptomyces* sp. and *S. atratus* produced amylase and pectinase at high and moderate levels, respectively. This study highlights the value of the studied isolates in providing bioactive metabolites and extracellular hydrolytic enzymes, indicating their potential application as fungal-biocontrol agents.

**Keywords:** biocontrol; phytopathogens; bioactive substances; microbial biostimulants; antagonistic activity; *Actinobacteria*
