## 4. Discussion
PGPR can also alter hormonal signaling from root to shoot, thereby improving salt tolerance in crops [25]. The siderophores production capacity of PGPR increases the availability of micronutrients for plants. Bacterial siderophores are used by plants as a source of iron. Additionally, bacterial siderophores act as protectors against pathogenic microorganisms and their deleterious effects on plant growth [26]. In the present study, 47.95% of the isolates were positive for the production of siderophores of which 48.93% were rhizosphere bacteria. Siderophores are Fe chelating compounds and have a strong affinity for iron. Siderophores make iron more accessible to plants by forming a Fe-siderophores complex. In saline and sodium soils, the level of iron available for uptake by plants is limited. Then in this type of soil, iron, and other micronutrients required by plants resulted in deficiency [27]. In parallel with auxin production, the growth of plants in these soil types is supported by rhizosphere bacteria producing siderophores. Volatile substances are also involved in the suppression of various pathogens. Ammonia produced as an intermediate in the amino acid catabolism of root exudates can help supply the nitrogen requirement of the host plant and in large amounts suppresses the colonization of plants by pathogens. The production of NH\({}_{3}\) was very common in isolated strains where 67.34% produced ammonia. This rate was comparable to those mentioned by several studies [3; 4]. HCN is a secondary metabolite produced by several PGPR. Although this compound is a general metabolic inhibitor, it is excreted as a means of avoiding predation or competition. It is highly toxic to all aerobic microorganisms, without affecting the producing microbes. In our study, 24.48% of the isolates could produce HCN. It has been shown that strains capable of producing HCN and siderophores showed inhibitory activity against several phytopathogenic fungi [28]. The existence of hydrolytic enzymes associated with PGPRs is a necessary characteristic to detect the most effective strains. Their presence limits the growth of fungal phytopathogens and reinforces the resistance of plants against these diseases [28]. The enzymatic potential of the isolates was evaluated by the production of amylase (92.85%), chitinase (61.22%), cellulase (41.83%), and protease (36.73%). chitinase, for example, breaks down the fungal cell wall and causes lysis of fungal cells. Additionally, the chitin and glucan oligomers released during the breakdown of the fungal cell wall act as elicitors that trigger various defense mechanisms in plants. These enzymes were produced by various bacteria such as _Pseudomonas stutzeri_ capable of lysing the pathogen _Fusarium_ sp. [23]. The antifungal activity carried out on 40 isolates selected according to their PGP activity, showed that 55% of them inhibited the growth of phytopathogenic fungi. The antifungal metabolites were more active against _A. niger_ where the majority (97.5%) of the strains inhibited it at a rate of 72.5% for the OE1 strain. On the other hand, _F. oxysporum_ was the least sensitive [4], it was inhibited at a rate of 44% (strain BR6). It has been well demonstrated that indigenous microorganisms associated with plants in agro-desert ecosystems have a significant antagonistic potential against phytopathogens [13]. In order to select strains tolerant to various abiotic constraints, 10 strains were evaluated for their ability to grow at different concentrations of NaCl, PEG8000, and different pH and temperature values. The majority of strains had grown in a wide range of stress tested. Most strains grew appreciably up to 400 mM NaCl and tolerated 20% PEG. These findings confirmed the close link between strain tolerance and their origin. Bacteria associated with halophytic plants can tolerate salt levels ranging from 4 to 30%.