## 1 Introduction  
Agricultural productivity enhancement through high chemical inputs (particularly nitrogen [N] and phosphorous [P]) represents an economically and environmentally unsustainable approach to reaching future food demand goals [1]. Implementing advanced technological solutions can mitigate fertilization-induced environmental impacts and economic burdens in agricultural production. These solutions focus on optimizing nutrient delivery, irrigation regimes, and soil cultivation techniques and utilizing novel crop varieties with enhanced nutrient use efficiency [2]. Furthermore, integrating microbial biotechnology, specifically harnessing beneficial plant-microbe and microbiome interactions, can significantly improve the efficacy of these on-arm mitigation strategies [3]. Thus, the development of effective microbial biofertilizers, i.e., products containing beneficial microorganisms (mainly fungi and bacteria) that can be applied to the plant [4], represents a promising and sustainable approach for enhancing soil fertility and promoting plant growth, contributing to minimize excessive synthetic fertilizer application, thus mitigating greenhouse gas emissions, water pollution, and soil degradation [5]. Microbial biofertilizers are primarily derived from the plant microbiome, a dynamic ecological community whose composition and function are modulated by a complex interplay of factors, including host plant genotype, edaphic properties, plant developmental stage, inter-microbial resource competition, and responses to abiotic stress [4; 5; 6; 7; 8]. Within the diverse plant microbiome, a select subset of microorganisms, known as plant growth-promoting rhizobacteria (PGPR), exhibit beneficial interactions with their host. PGPR has been extensively documented to improve plant nutritional status through various mechanisms, including direct nutrient provision, for example, through N fixation [9; 10; 11], the transformation of nutrients into more readily assimilable forms, like solubilizing inorganic soil phosphates [12] or iron (Fe) through siderophores [13; 14], and modulation of root architecture to enhance nutrient uptake efficiency [15; 16; 17]. Synthetic Microbial Communities (SynComs) are rationally designed microbial consortia engineered to replicate key interactions and functionalities observed in natural microbiomes, offering a simplified model system with reduced complexity [18]. Low-complexity synthetic microbial consortia, composed of a limited number (1-10) of microbial strains with documented plant growth-promoting activities, represent a promising approach for enhancing plant growth [19; 20; 21]. Compared to a single strain's application, the employment of SynCom aims at (1) increasing the abundance of functionally similar microbial populations: by introducing multiple strains with similar metabolic capabilities (e.g., N fixation, phosphate solubilization), the overall efficiency of these PGP traits can be amplified, potentially leading to increased nutrient availability for the plant; (2) providing the plant with a diverse range of PGP functionalities: combining strains with different PGP mechanisms (e.g., one strain for auxin production, another for siderophore production, a third for biocontrol, etc.) offers a more holistic approach to plant growth promotion, addressing multiple needs simultaneously [5; 22]. Harnessing this potential, SynCom, composed of strains selected for specific plant growth-promoting traits and stress tolerance, can be developed as an effective inoculant to facilitate plant growth even in adverse environments. Isolation of new strains to be harnessed as PGPR is essential to enhance the diversity of available strains for various environmental conditions and plant species and increase the understanding of plant-microbe interactions. Plants grown in marginal areas, where climate change increasingly challenges plant survival, may harbor unique microbial communities that can serve as reservoirs of microorganisms adapted to drought, high salinity, and nutrient deficiency [23].