Harnessing rhizosphere microbes: the synergistic roles of PGPR and AMF in sustainable tomato production under stress

Abstract

Tomato (Lycopersicon esculentum L.) is among the most economically important vegetable crops worldwide, yet its production is severely constrained by multiple biotic and abiotic stresses, including pathogens, pests, drought, salinity, and heavy metal toxicity. Amid intensifying climate change and increasing demands for sustainable agriculture, plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF) have emerged as key beneficial rhizospheric microorganisms with significant potential for enhancing plant stress tolerance and promoting growth. PGPR directly promote the growth of tomato plants through biological nitrogen fixation, solubilization of phosphate and potassium, siderophore-mediated iron uptake, and the production of phytohormones. Indirectly, PGPR suppress pathogens, activate induced systemic resistance (ISR), reinforce cell walls, enhance the activities of antioxidant enzymes, and regulate the accumulation of osmolytes. AMF form symbiotic associations with the roots of tomato plants, enhancing nutrient and water absorption via extraradical mycelial networks, improving phosphorus and nitrogen uptake, modulating abscisic acid (ABA), jasmonic acid (JA), and strigolactone signaling pathways, activating mycorrhiza-induced resistance (MIR), and enhancing photosynthetic efficiency and water-use efficiency under stress. The co-inoculation of PGPR and AMF yields synergistic effects by facilitating mutual colonization, optimizing nutrient bioavailability, coordinately strengthening antioxidant and osmotic regulation systems, and reinforcing systemic defense responses, thereby conferring more robust and efficient stress tolerance than single inoculations. Despite significant advances, key challenges persist in elucidating tripartite molecular crosstalk, maintaining stability during field applications, and developing tailored microbial consortia. This review synthesizes the individual and synergistic mechanisms through which PGPR and AMF enhance the resilience of tomato plants to biotic and abiotic stresses, offering valuable insights for engineering microbial communities to enhance stress resistance in crops.

1. Introduction

Tomato (Lycopersicon esculentum L.) is an economically important crop cultivated worldwide. According to the Food and Agriculture Organization (FAO), the global production of fresh tomatoes reached approximately 192 million tonnes in 2023. The consumption of tomatoes continues to rise worldwide, driven by demand from both the fresh market and the processed food industry (Liu et al., 2022; Li Q. et al., 2023). The widespread consumption of this fruit stems from its high nutritional value, being a rich source of bioactive compounds, including carotenoids such as lycopene and β-carotene, phenolic substances such as flavonoids, and essential vitamins such as ascorbic acid (vitamin C), α-tocopherol (vitamin E), and vitamin A (Kumar et al., 2021; Naik et al., 2023). Additionally, tomatoes contain other functional constituents, including glycoalkaloids such as tomatine, as well as diverse phytosterols, including β-sitosterol, campesterol, and stigmasterol (Kumar et al., 2021). Among these, lycopene is the primary pigment responsible for the characteristic red color of ripe tomatoes and is known for its potent antioxidant properties. Tomatoes serve as the principal commercial source of lycopene, supplying approximately 80% of the global industrial demand (Kumar et al., 2021; Tufail et al., 2024). Nevertheless, tomato cultivation is increasingly challenged by a range of abiotic and biotic stressors. The abiotic stressors include drought, salinity, temperature extremes, and nutrient deficiencies, whereas biotic stresses arise from infestations by pests and pathogens, including insects, fungi, bacteria, nematodes, and viruses (Soltabayeva et al., 2022; Li W. et al., 2023; Shi et al., 2025). Collectively, these stresses impair plant growth, development, and yield. Climate change has further exacerbated the frequency and intensity of abiotic stresses—particularly drought, heat, salinity, and flooding—thereby threatening future crop productivity (Zhang et al., 2014; Rai et al., 2022; Shawky et al., 2024). Drought stress, in particular, triggers complex molecular and cellular responses that affect nearly all physiological processes (Zhang et al., 2014). Water scarcity affects the majority of plant functions through direct or indirect mechanisms. Despite species-specific variations, plants generally perceive environmental stress signals and transduce them internally to activate appropriate defense mechanisms (Golldack et al., 2014). To mitigate drought effects, plants adjust root architecture, enhance osmotic regulation, optimize water-use efficiency (WUE), enhance the activities of antioxidant enzymes, and reduce stomatal conductance (Gs) to conserve water (Sun et al., 2020). These stress responses are largely mediated by phytohormones and signaling molecules, with abscisic acid (ABA) being the most extensively studied phytohormone in the context of abiotic stress, particularly drought. The levels of ABA rise rapidly under stress and play a central role in regulating stomatal closure, plant growth suppression, and the activation of defense pathways (Peleg and Blumwald, 2011; Osakabe et al., 2014; Muhammad Aslam et al., 2022). Beyond intrinsic defense mechanisms, plants establish symbiotic associations with rhizospheric microorganisms to alleviate stress. These include naturally occurring or deliberately introduced microbes, such as plant growth-promoting rhizobacteria (PGPR) and arbuscular mycorrhizal fungi (AMF), both of which have been shown to significantly enhance plant resilience under adverse conditions (Ton et al., 2009; Ruiz-Lozano et al., 2016; Han Y. et al., 2022).

PGPR and AMF, including strains applied to mitigate salinity stress, play vital roles in enhancing plant survival under adverse conditions (Li W. et al., 2023; Mazumder et al., 2025). Certain PGPR function as biological control agents by inhibiting spoilage organisms and offer a safer alternative to synthetic agrochemicals that may pose risks to human health, livestock, and beneficial soil microbes (Adedayo et al., 2022). The application of AMF provides an effective and environmentally sustainable strategy for mitigating the negative effects of abiotic stresses, including salinity, drought, temperature extremes, and heavy metal toxicity (Chandrasekaran et al., 2021). These microorganisms support plant growth, activate defense responses, enhance stress tolerance, and contribute to successful fruit development. This review comprehensively examines the roles of PGPR and AMF in promoting the health of tomato plants, with particular emphasis on the regulatory mechanisms underlying resistance to biotic and abiotic stressors.

2. Microbial influences on plant stress responses

Over hundreds of millions of years of co-evolution, plants have developed intricate associations with a diverse array of microorganisms, including bacteria, fungi, archaea, protists, and viruses (Gong and Xin, 2021). Bacteria and fungi constitute the majority of microbial biomass within these communities. Such symbiotic interactions have been fundamental in shaping plant adaptability to both biotic and abiotic stresses (Gong and Xin, 2021; Bai et al., 2022; Xiong and Lu, 2022). The assembly and stability of these microbial communities are governed by host plant selection, microbial dispersal from surrounding environments, and interspecies interactions (Trivedi et al., 2020; Zeng et al., 2025). Under stress conditions, plants alter their metabolism and root exudation patterns, thereby reshaping the composition and function of associated microbial communities to enhance stress tolerance (Santos-Medellín et al., 2017; Timm et al., 2018; Ge et al., 2023). These plant–microbe interactions contribute to the establishment of specialized ecological niches that facilitate microbial colonization and promote host growth and defense capacity (Stringlis et al., 2018). Plants actively recruit beneficial microbes under biotic stress to suppress the growth of pathogens (Ge et al., 2023). Plant-associated microbiomes form highly interactive ecological networks that become more robust under environmental stress conditions (Soliveres et al., 2014; Toju et al., 2018). Beneficial microorganisms compete with pathogens for critical resources, including siderophores and essential nutrients, thereby suppressing pathogen proliferation and reducing virulence (Raaijmakers and Mazzola, 2012). In disease-suppressive soils, the roots of sugar beet are enriched with microbial families such as Chitinophagaceae and Flavobacteriaceae, which express defense-related enzymes—including chitinase, nonribosomal peptide synthetase (NRPS), and polyketide synthase (PKS)—in response to pathogen attacks, thereby conferring resistance against Rhizoctonia solani (Mendes et al., 2011; Chapelle et al., 2016; Carrión et al., 2018). Similarly, resident soil bacteria suppress the growth of Ralstonia solanacearum through competition for essential resources. In the rhizospheres of healthy tomato plants, microbial communities are enriched in beneficial taxa, including Actinobacteria and Firmicutes, which comprise numerous biocontrol agents (Wei et al., 2015; Su et al., 2020). It has been reported that species with the genera Bacillus and Pseudomonas produce antibiotics with antibacterial, insecticidal, and antiviral activities. By occupying ecological niches and restricting pathogen access to nutrients, these beneficial microorganisms contribute to plant health and are widely used in biocontrol strategies (Zelezniak et al., 2015; Koprivova et al., 2019). In Arabidopsis thaliana, infection by Hyaloperonospora arabidopsidis or Botrytis cinerea induces the recruitment of specific bacterial consortia that enhance plant defense responses (Berendsen et al., 2018). In summary, beneficial microorganisms play a pivotal role in mitigating biotic stress through direct competition with pathogens and the production of antimicrobial compounds, thereby enhancing plant fitness and reducing disease incidence.

Plants can also enhance their growth under abiotic stress by recruiting beneficial microorganisms (Ge et al., 2023), which contribute to drought tolerance by enhancing the activities of antioxidant enzymes, improving WUE, modulating the production of phytohormones such as ABA, and facilitating nutrient uptake. In response to drought, microbial communities restructure their composition to support plant recovery, thereby enhancing adaptability and productivity under conditions of water limitation (de Vries et al., 2020). In rice, drought conditions significantly alter both bacterial and fungal communities in the rhizosphere and endosphere, thereby favoring the enrichment of taxa such as Actinobacteria and Chloroflexi, while reducing the abundance of Acidobacteria and Deltaproteobacteria. These shifts suggest that drought conditions selectively modulate the rhizospheric microbiome to enhance plant survival (Santos-Medellín et al., 2017). Under aluminum stress, aluminum-tolerant soybean genotypes recruit diverse microbial taxa, including Tumebacillus, Granulicella, and Burkholderia, which enhance plant resistance by increasing the activities of soil enzymes and reshaping bacterial community structure (Lian et al., 2019). Similarly, methylotrophic bacteria, including Methylobacterium oryzae and Burkholderia spp., can reduce the accumulation of heavy metals such as nickel and cadmium in tomato plants by restricting metal uptake and translocation, while concurrently suppressing stress-induced ethylene emissions (Madhaiyan et al., 2007).

Microbial inoculation supports plant survival in saline environments by enhancing the synthesis of osmoprotectants, such as glycine betaine and proline, and by activating antioxidant enzymes, including superoxide dismutase (SOD) and catalase (CAT). These responses help maintain osmotic balance and mitigate oxidative damage, thereby enhancing salt tolerance (Dimkpa et al., 2009). For instance, PGPR strains such as Pseudomonas pseudoalcaligenes and Bacillus pumilus have been shown to reduce lipid peroxidation, SOD and caspase-like activities, and programmed cell death in rice, thereby enhancing salinity tolerance in rice plants (Nonaka and Ezura, 2014; Jha and Subramanian, 2014; Bright et al., 2025). These PGPR strains also regulate the activities of antioxidant enzymes and stabilize cell membranes, further promoting plant growth under stress (Jha and Subramanian, 2014). Additionally, Azospirillum brasilense and various Bacillus spp. have been shown to support the production of osmolytes and suppress the biosynthesis of ethylene through the activity of 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase. This enzymatic activity reduces the accumulation of reactive oxygen species (ROS) and strengthens the intrinsic antioxidant defense mechanism in plants (Nonaka and Ezura, 2014; Degon et al., 2023; Kaundal et al., 2025). Collectively, these observations underscore the critical role of plant–microbe interactions in regulating plant responses to abiotic stress. A deeper understanding of these mechanisms offers valuable opportunities to harness microbial strategies for enhancing plant resilience and productivity under adverse environmental conditions (Figure 1).

Figure 1.

Schematic representation of the role of beneficial microorganisms in enhancing soil fertility and nutrient uptake by plants. Beneficial microorganisms improve soil health by enhancing soil moisture retention, quality, and fertility levels. These improvements facilitate nutrient uptake through specific transportation mechanisms and root morphology modification, enabling efficient translocation from the external environment to internal plant tissues. Concurrently, microorganisms bolster stress tolerance via upregulation of the antioxidant system and downregulation of lipoxygenase, thereby regulating ABA-responsive genes, aquaporin genes, phytohormone biosynthesis pathways, and transcription factors. The synergistic integration of these processes ultimately results in improved stress tolerance and enhanced crop yield.

3. PGPR and tomato plants

PGPR are soil-dwelling bacteria that colonize plant roots and enhance plant growth (dos Santos et al., 2020; Nwachukwu et al., 2021). They improve plant health by directly modulating plant metabolism through their metabolic products, promoting root development, increasing enzyme activity, enhancing yield, and combating diseases (Fasusi et al., 2021; Zia et al., 2021). Additionally, these bacteria provide indirect protection by competing with phytopathogens for essential nutrients and space, producing antimicrobial compounds that inhibit pathogen germination, and inducing systemic defense responses in host plants (Basu et al., 2021). Furthermore, PGPR facilitate plant survival under abiotic stress conditions by enhancing fitness, increasing stress tolerance, and promoting phytoremediation potential (Brunetti et al., 2021; Ali et al., 2023). Current research aims to elucidate the rhizospheric bacterial systems that interact with plant roots and support their growth (Gómez-Godínez et al., 2023). The modifications induced by PGPR in plants are diverse, with growth promotion likely arising from a complex interplay among multiple pathways influencing both development and nutrition acquisition (Vocciante et al., 2022). PGPR exert beneficial effects on plant growth via direct and indirect mechanisms, with their impact on plant development representing a multifaceted process that varies depending on the specific bacterium and plant species involved (Mokrani et al., 2020) (Figure 2). The direct mechanisms underlying the enhancement of plant growth by PGPR include increased nutrient uptake and the modulation of plant hormone levels (Mohanty et al., 2021; Melini et al., 2023), whereas the indirect effects encompass a range of strategies for the prevention or management of plant diseases (Mekonnen and Kibret, 2021).

Figure 2.

Diagram illustrating the direct and indirect mechanisms of plant growth promoting rhizobacteria (PGPR) in tomato plants.

3.1. Roles of PGPR in promoting growth and nutrient utilization in tomato

Nitrogen is an abundant and essential macronutrient for plant growth and various metabolic processes (Govindasamy et al., 2023); however, its atmospheric form cannot be directly absorbed by plants and must be converted into ammonia (NH₃) for utilization. PGPR mediate this conversion through biological nitrogen fixation (Klimasmith and Kent, 2022), with typical nitrogen-fixing PGPR species belonging to the genera Azotobacter, Azospirillum, Burkholderia, Bradyrhizobium, Enterobacter, Gluconacetobacter, and Stenotrophomonas (Singh et al., 2020). As the second most essential macronutrient, phosphorus is indispensable for photosynthesis, metabolism, and energy transfer in plants (Khan et al., 2023). PGPR can enhance the availability of soil phosphorus by mineralizing organic phosphorus and solubilizing insoluble inorganic phosphate—processes that are strongly influenced by soil pH (Cheng X. et al., 2023). These bacteria lower rhizospheric pH by secreting organic and inorganic acids, thereby enhancing soil phosphate bioavailability (Johan et al., 2021). Representative phosphate-solubilizing bacteria include members of the genera Rhizobium, Pseudomonas, and Bacillus (Kalayu, 2019).

Potassium, the seventh most abundant element in the Earth’s crust, is another essential macronutrient, following nitrogen and phosphorus (Dhillon et al., 2019; Olaniyan et al., 2022). Potassium participates in numerous metabolic and developmental processes and activates over 80 enzymes involved in starch synthesis, nitrate reduction, photosynthesis, and energy metabolism. An adequate supply of soil potassium has been shown to enhance plant vigor and increase resistance to biotic stresses, diseases, and pests (Srinivasarao et al., 2016). Efficient potassium-solubilizing strains include Bacillus mucilaginosus, Bacillus edaphicus, and Bacillus circulans (Umar et al., 2020; Kumar and Nautiyal, 2022). Iron is an essential micronutrient for all living organisms (Ferreira et al., 2019); however, its predominant naturally occurring form, Fe³⁺, exhibits low solubility and limited bioavailability (Timofeeva et al., 2022). Under conditions of iron limitation, PGPR secrete siderophores that chelate Fe³⁺, thereby enhancing iron uptake for plant growth while simultaneously competing with phytopathogens for iron and suppressing their proliferation (Hakim et al., 2021; Molnár et al., 2023; de Andrade et al., 2023).

Beyond nutrient acquisition, phytohormone production represents another key mechanism through which PGPR promote the growth of tomato plants (Kudoyarova et al., 2019). PGPR synthesize various phytohormones, including gibberellins, cytokinins, ABA, ethylene, auxins, and indole-3-acetic acid (IAA), which stimulate the proliferation of lateral roots, improve nutrient and water absorption, and support root cell development (Mukherjee et al., 2022; Sosnowski et al., 2023). Among these, IAA serves as a key phytohormone in plant–microbe interactions, whereas auxin production has been shown to modulate hormonal balance in plants, increase root biomass, and reduce stomatal size and density. In contrast, gibberellins and cytokinins promote shoot growth and facilitate root exudation (Backer et al., 2018; Lopes et al., 2021; Vocciante et al., 2022). The introduction of PGPR inoculants, including Pseudomonas and Bacillus spp., during tomato cultivation accelerates seed germination and enhances plant height, root length, leaf number, and fruit weight, often by improving phytohormone balance, nutrient availability, antimicrobial activity, and systemic resistance (Ketut Widnyana, 2019). Strains such as Burkholderia contaminans AY001 exhibit strong plant growth-promoting traits, including nitrogen fixation, phosphate solubilization, and IAA production, while also suppressing the growth of soil-borne pathogens and inducing systemic resistance in tomato plants (Heo et al., 2022). It has been demonstrated that the co-application of PGPR and AMF further enhances the uptake of potassium, activities of antioxidant enzymes, and accumulation of lycopene in tomato fruits, demonstrating synergistic effects on nutrient use efficiency and fruit quality (Ordookhani et al., 2010). Collectively, PGPR enhance the growth of tomato plants by improving nutrient availability, producing beneficial phytohormones, regulating root development, and supporting overall physiological vigor under diverse growth conditions.

3.2. PGPR as biocontrol agents and inducers of systemic resistance in tomato

Beyond their direct effects on promoting plant growth, PGPR significantly contribute to plant development by suppressing diseases and enhancing tolerance to biotic stressors (El-Saadony et al., 2022). This protective effect is primarily achieved through the microbial antagonism of pathogens and the stimulation of defense systems in the host plant. The resistance induced in plants typically arises from the activation of effective defense mechanisms, particularly systemic acquired resistance (SAR) and induced systemic resistance (ISR) (Bhadrecha and Bhawana, 2023). Signaling hormones, including salicylic acid (SA) and jasmonic acid (JA), serve as key regulators of these response pathways and represent core components of plant innate immunity (Yu et al., 2022).

In addition, PGPR can trigger ISR, with certain rhizobacterial strains conferring enhanced resistance against various pathogens, including Fusarium oxysporum and Colletotrichum orbiculare (Wei et al., 1991). Among PGPR, strains of Pseudomonas, Bacillus, and Serratia are the most extensively studied for their ability to elicit ISR (Meena et al., 2020). However, distinguishing ISR triggered by beneficial microbes from similar stress responses induced by pathogenic microorganisms remains challenging, as both activate analogous signaling pathways (Zhu et al., 2022). Numerous bacterial elicitors of ISR have been identified over recent decades, including quorum-sensing molecules, flagellin, acyl-homoserine lactones (AHLs), exopolysaccharides, lipopolysaccharides, and various secreted metabolites (Nag et al., 2021).

After perceiving non-pathogenic PGPR such as Pseudomonas fluorescens or Bacillus subtilis, tomato plants activate multiple layered defense mechanisms, including callose deposition, synthesis of phytoalexins, and upregulation of pathogenesis-related (PR) proteins (Yu et al., 2022; Joshi et al., 2023). These defense responses closely resemble those mounted during pathogenic infection. Additionally, PGPR reinforce physical defense barriers by modifying plant cell wall structure and promoting the deposition of lignin (Kaur et al., 2022).

Although functionally analogous to pathogen-induced SAR, the ISR mediated by beneficial bacteria distinctly relies on the NPR1 (nonexpressor of pathogenesis related genes 1) protein (Panpatte et al., 2020). In the SAR pathway, both NPR1 and TGA transcription factors (bZIP transcription factor) play an essential role in the transduction of SA signals, and their expression is further modulated by components of the MAPK (mitogen-activated protein kinase) signaling cascade (Han Q. et al., 2022; Zhao et al., 2024).

Inoculation with PGPR during tomato cultivation effectively reprograms defense metabolism, leading to the elevated accumulation of hydroxycinnamic acids, benzoic acid derivatives, flavonoids, and glycoalkaloids, thereby establishing a primed or “pre-stimulated” defensive state that enhances resistance to pathogens and herbivores (Mhlongo et al., 2020, 2022). For instance, Klebsiella sp. JCK-2201, which produces meso-2,3-butanediol, has been shown to alleviate bacterial wilt in tomato by upregulating defense-related genes and activating the SA and JA signaling pathways (Kim et al., 2022). Endophytic Bacillus sp. and Pseudomonas aeruginosa enhance resistance to cutworms by modulating the levels of IAA, SA, and ABA in tomato, while increasing the contents of phenolics and flavonoids and enhancing fruit yield (Kousar et al., 2020). Bacillus subtilis NSY50 promotes growth and photosynthetic efficiency in tomato while mitigating Fusarium wilt by regulating hormone signaling and the synthesis of secondary metabolites (Du et al., 2022). Similarly, Burkholderia contaminans AY001 displays multiple beneficial traits in plants and induces systemic resistance in tomato against Fusarium oxysporum f. sp. lycopersici and Pseudomonas syringae pv. (Heo et al., 2022). Collectively, PGPR enhance tolerance to biotic stresses in tomato through hormone modulation, defense priming, cell wall reinforcement, and the induction of systemic resistance, thus establishing these bacteria as sustainable and effective biocontrol agents in tomato production systems.

3.3. Role of PGPR in mitigating abiotic stress in tomato

PGPR act as eco-friendly biological stimulators that enhance the tolerance of tomato plants to various abiotic stresses, including drought, salinity, nutrient deficiency, and heavy metal toxicity, thereby supporting sustainable agricultural production (Numan et al., 2018). PGPR-mediated stress tolerance relies on coordinated physiological, biochemical, and molecular modifications, including improved nutrient acquisition, regulated phytohormone balance, enhanced antioxidant systems, stabilized osmotic equilibrium, optimized root system architecture, and reinforced root cell wall structures. Together, these integrated mechanisms alleviate stress-induced damage and help maintain normal growth and productivity in tomato under adverse environmental conditions (Figure 2).

The rhizosphere harbors abundant PGPR that form mutualistic interactions with the roots of tomato plants and promote plant growth through direct and indirect mechanisms (Martínez-Viveros et al., 2010; Garcia-Lemos et al., 2020). PGPR can directly promote plant growth through biological nitrogen fixation; solubilization of insoluble phosphorus, zinc, and potassium; and the synthesis of key phytohormones, including auxins, cytokinins, gibberellins, ethylene, and ABA (Großkinsky et al., 2016; Chauhan et al., 2021). These phytohormones regulate cell division, root elongation, development of lateral roots, and overall plant morphogenesis. Auxins, in particular, modify root architecture by promoting pericycle cell division, initiation of lateral root primordia, formation of root hairs, and primary root elongation, which markedly enhance water and nutrient uptake under conditions of drought and nutrient limitation (Tripathi et al., 2021; Roychoudhry and Kepinski, 2022). PGPR can indirectly promote plant growth and enhance stress adaptation in tomato through the biocontrol of soil-borne pathogens, production of siderophores, and the competitive exclusion of harmful microbes (Bal and Chanway, 2012; Glick, 2012). PGPR colonize root surfaces and internal tissues in tomato cultivation systems, facilitating nutrient uptake and enhancing tolerance to salinity, drought, and other environmental constraints (Jambon et al., 2018; Numan et al., 2018). When applied via seed priming or soil inoculation, PGPR strains such as Pseudomonas and Bacillus spp. accelerate seed germination, increase biomass accumulation, and improve fruit yield by enhancing nutrient availability, phytohormone production, and systemic stress resistance (Ketut Widnyana, 2019).

Abiotic stresses, including drought, salinity, and nutrient imbalances, induce the excessive accumulation of ROS in tomato plants, leading to oxidative damage, peroxidation of membrane lipids, protein denaturation, and disruption of cellular functions (Lanza and Reis, 2021; Zandi and Schnug, 2022). Under optimal conditions, plants maintain ROS homeostasis through intrinsic scavenging systems; however, exposure to severe stress frequently surpasses the capacity of these protective mechanisms (Hasanuzzaman et al., 2020). PGPR directly mitigate oxidative stress in plants by producing antioxidants and activating endogenous antioxidant defense pathways (Nivetha et al., 2021). The major enzymatic antioxidants induced by PGPR include SOD, CAT, and peroxidase (POD), which function sequentially to scavenge superoxide anions and hydrogen peroxide (H₂O₂), thereby mitigating oxidative stress (Jomova et al., 2024). PGPR also induce the accumulation of non-enzymatic antioxidants, including ascorbic acid and glutathione, which function synergistically in the ascorbate-glutathione cycle to efficiently scavenge ROS and maintain cellular redox balance (Zandi and Schnug, 2022; Mhamdi, 2023). PGPR modulate molecular signaling in their host plants to upregulate the expression of antioxidant genes, thereby conferring enhanced stress tolerance in tomato plants under harsh environmental conditions (Wahab et al., 2023a, 2023b).

Drought and salinity stress severely disrupt cellular osmotic balance in tomato plants, thereby impairing water uptake and inducing dehydration-related damage (Kumar et al., 2023). PGPR alleviate osmotic stress by promoting the synthesis and accumulation of compatible osmolytes, including proline and glycine betaine (Haghpanah et al., 2024). Proline functions as an effective osmoprotectant by maintaining cell turgor, stabilizing proteins and membranes, and directly scavenging ROS (Pattnaik et al., 2021). PGPR enhance the accumulation of proline by upregulating key biosynthetic genes, including Δ¹-pyrroline-5-carboxylate synthetase (P5CS), under stress conditions (Hasanuzzaman et al., 2021). Similarly, glycine betaine maintains osmotic potential in the cytoplasm and vacuoles, thereby protecting tomato plants from drought and salinity-induced injuries (Rasheed et al., 2024). By stabilizing the osmotic equilibrium, PGPR enable tomato plants to retain water and sustain normal metabolic activities under abiotic stress conditions.

In addition, PGPR can significantly modify the architecture of tomato root systems by regulating root elongation, formation of lateral roots, proliferation of root hairs, and the spatial distribution of roots (Verma et al., 2022; Khan et al., 2021). These modifications are primarily mediated by PGPR-derived phytohormones, particularly through the dynamic balance between auxins and cytokinins (Pantoja-Guerra et al., 2023). Auxins promote the elongation of primary roots and the development of lateral roots, whereas cytokinins stimulate cell division and growth of root hairs, which collectively enhance the absorption area of roots (EL Sabagh et al., 2022; Wahab et al., 2025). PGPR strains, such as Azospirillum brasiliense and Bacillus licheniformis, enhance root growth in tomato plants via phytohormone production, thereby enhancing access to water and nutrients under conditions of drought and nutrient deficiency (Raja Gopalan et al., 2023). The optimized root system facilitates more efficient phosphate solubilization, nitrogen fixation, and siderophore-mediated iron acquisition, thereby further enhancing stress adaptation (Sagar et al., 2021; Hassen et al., 2023). Studies have demonstrated that PGPR-inoculated tomato plants consistently exhibit greater root length, density, and branching under conditions of abiotic stress compared to those of non-inoculated controls.

In addition to hormonal and metabolic regulation, PGPR enhance stress tolerance in tomato plants by remodeling the physicochemical properties of root cell walls (Vandana et al., 2021; Grover et al., 2021). The inoculation of PGPR induces the deposition of lignin and callose, which reinforce cell wall rigidity, enhance mechanical stability, and mitigate stress-induced damage (Choudhary et al., 2016; Chang et al., 2023). These cell wall modifications are key components of ISR, which not only confers resistance against biotic stresses but also contributes to abiotic stress tolerance (Sood et al., 2021; Wahab et al., 2025). PGPR-mediated cell wall fortification reduces cell wall plasticity and enhances the structural integrity of roots, thereby supporting continuous root growth under saline, drought, and heavy metal stress conditions (Srivastava et al., 2023).

In practical agricultural systems, PGPR effectively improve the performance of tomato plants under conditions of salinity, drought, nutrient limitation, and heavy metal stress. Halotolerant PGPR such as Streptomyces sp. KLBMPS084 enhance salt tolerance by increasing the activities of antioxidant enzymes, levels of osmoprotectants, and expression of stress-related genes (Gong et al., 2020). Under conditions of cadmium or chromium stress, PGPR reduce metal uptake, activate antioxidant systems, and promote plant growth by inducing the production of IAA and increasing phosphate solubilization (Gupta et al., 2020; Sarwar et al., 2022; Zhang et al., 2023; Zhou W. et al., 2022, 2024). The co-inoculation of PGPR with AMF has been shown to further enhance the content of lycopene, induce antioxidant activity, and increase the accumulation of potassium in tomato fruits (Ordookhani et al., 2010). Collectively, PGPR enhance the resilience of tomato plants to abiotic stresses through integrated and coordinated mechanisms, including phytohormone modulation, activation of antioxidant defense systems, osmotic adjustment, optimization of root architecture, reinforcement of cell wall integrity, and improved nutrient acquisition. These multifunctional benefits highlight the potential of PGPR as sustainable and effective biostimulants for enhancing the stability of tomato production under adverse environmental conditions.

4. AMF and growth of tomato plants

4.1. Symbiotic mechanisms of AMF in regulating tomato growth and stress resistance

AMF, belonging to the phylum Glomeromycota are primarily classified into four orders, namely, Glomerales, Archaeosporales, Paraglomerales, and Diversisporales, which are further subdivided into 25 genera based on morphological features within the broader taxonomic framework (Redecker et al., 2013). AMF are obligate biotrophs that establish mutualistic associations with the majority of flowering plants (Bonfante and Genre, 2010). In plant–AMF symbiotic associations, AMF connect plant roots to the surrounding soil via intraradical hyphae (IRH), which penetrate the outer cortical cells of plant roots and form hyphal coils enclosed by a plant-derived plasma membrane (Genre et al., 2020). Within the inner cortical cells, AMF form arbuscules that are surrounded by plant-derived perifungal membranes, thereby establishing the peri-arbuscular space (PAS). This compartment serves as the site for bidirectional nutrient exchange between the AMF and the host plant (Wipf et al., 2019; Duan et al., 2024). Colonization by AMF significantly enhances nutrient absorption, increases stress tolerance, and alters the composition of the rhizospheric microbiome by recruiting other beneficial microorganisms. This symbiotic interaction plays a critical role in shaping the microbial ecology of the rhizosphere and supporting overall plant health (Cheng Y. et al., 2023; Boyno et al., 2025). AMF contribute to enhanced plant growth, improved mineral nutrition, and increased resilience against abiotic stresses, including drought, salinity, and heavy metal toxicity, as well as biotic stresses such as soil-borne diseases (Figure 3) (Lenoir et al., 2016; Brar et al., 2024; Sun et al., 2024). AMF enhance the performance of tomato plants during cultivation by promoting the uptake of phosphorus and nitrogen, modulating hormonal signaling, enhancing the activities of antioxidant enzymes, and improving WUE. These benefits contribute to higher yield and fruit quality, highlighting AMF as a promising biotechnological tool for promoting sustainable agriculture (Chandrasekaran et al., 2021).

Figure 3.

AMF enhance plant stress resilience through multiple synergistic pathways. These pathways include promoting photosynthetic efficiency, optimizing the root-to-stem ratio for improved resource allocation, expanding root surface area, and facilitating the uptake of nutrients such as nitrogen, phosphorus, and potassium via extraradical mycelium and arbuscular structures. Additionally, AMF boost metabolic processes, regulate hormonal balance—particularly involving abscisic acid and strigolactones—stimulate the activity of antioxidant enzymes (including superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase), and interact with other beneficial microorganisms in the hyphosphere. Key structural features of AMF involved in these processes include spores, extraradical mycelium, hyphopodia, hyphal branching, hyphal coils, and arbuscules, which collectively support nutrient exchange, colonization, and the regulation of stress responses.

4.2. AMF-mediated biocontrol and disease resistance in tomato

Numerous studies have confirmed that AMF enhance plant resistance to a wide range of pathogens (Umer et al., 2025). AMF have also been shown to interact synergistically with various rhizospheric microbes, including those in the genera Trichoderma, Pseudomonas, and Bacillus, thereby improving collective biocontrol efficacy against pathogenic bacteria, fungi, and nematodes (Umer et al., 2025). This synergy is achieved through the enhanced secretion of antimicrobial compounds, activation of plant defense pathways, and modification of the rhizospheric microbiome, thereby creating an unfavorable environment for plant pathogens (Umer et al., 2025; Farhaoui et al., 2025). AMF have been shown to effectively suppress soil-borne fungal pathogens responsible for root rot and wilt diseases in various crops, as well as foliar pathogens such as Alternaria solani, which affects tomato plants (Harrier and Watson, 2004).

Mycorrhizal symbiosis confers broad-spectrum protection against viruses, bacteria, phytoplasmas, fungi, and herbivorous pests through three interconnected mechanisms (Comby et al., 2017). First, AMF enhance photosynthetic efficiency and the acquisition of nutrients, particularly phosphorus and nitrogen, thereby strengthening host vigor and increasing resistance to pathogen colonization and proliferation (van der Heijden et al., 2006; Hildebrandt et al., 2007). Second, the extraradical mycelium (ERM) of AMF modulates the rhizospheric microbiome by competing spatially and nutritionally with soil-borne pathogens, while simultaneously stimulating the activity of PGPR, including nitrogen-fixing and phosphate-solubilizing bacteria, which further suppress pathogenic microorganisms (Schouteden et al., 2015; Pérez-de-Luque et al., 2017; Nacoon et al., 2020). Third, AMF establish common mycorrhizal networks (CMNs) among conspecific or heterospecific plants, thereby facilitating long-distance nutrient translocation and interplant signal transfer, including the induction of membrane depolarization (Babikova et al., 2013; Johnson and Gilbert, 2015; Bücking et al., 2016). These CMNs facilitate the transmission of defense signals from AMF-colonized plants under attack by caterpillars or necrotrophic fungi to neighboring plants, thereby triggering the preemptive activation of plant defense responses (Babikova et al., 2013, 2014; Song et al., 2010, 2015).

The establishment of plant–AMF symbiosis initiates a tightly regulated immune response cascade in the host plant. During the early stages of the symbiotic interaction, plant pattern recognition receptors (PRRs) recognize AMF-secreted microbe-associated molecular patterns (MAMPs), thereby triggering local MAMP-triggered immunity (MTI) in roots and concomitant SA biosynthesis (Zhang and Zhou, 2010; Zamioudis and Pieterse, 2012). SA-derived long-distance signals systemically prime SA-dependent defenses in aerial tissues; however, elevated SA levels in roots inhibit the colonization of AMF (De Román et al., 2011; Cameron et al., 2013). In response, AMF secrete effector proteins that induce the production of ABA in roots, leading to the local suppression of SA-mediated defense mechanisms and successful root colonization. Additionally, ABA translocates to aerial tissues via the xylem, thereby reinforcing cell wall defenses against foliar pathogens (Ton et al., 2009; Trouvelot et al., 2015). Once symbiosis is established, AMF induce systemic mycorrhiza-induced resistance (MIR) in the distal tissues of the host plant (Jung et al., 2012). Cordier et al. confirmed this phenotype using a split-root system, in which tomato roots colonized by Funneliformis mosseae (syn. Glomus mosseae) conferred resistance to Phytophthora nicotianae var. parasitica in non-mycorrhizal roots, thereby reducing necrosis and the growth of pathogen mycelia via the accumulation of non-esterified pectins and PR1a proteins in the cell wall (Delaeter et al., 2024). MIR is predominantly governed by hormonal signaling networks, and although it may occasionally resemble SA-dependent SAR, it more frequently aligns with JA/ethylene-dependent ISR (Trouvelot et al., 2015). Furthermore, AMF modulate MIR by enhancing phosphate uptake by plant roots and the translocation of photosynthates to the roots, thereby altering the composition of root exudates to recruit beneficial rhizobacteria, including Pseudomonas and Burkholderia spp., which secrete signaling compounds that amplify JA/ethylene-dependent ISR via long-distance systemic priming (Liu et al., 2007; Van der Ent et al., 2009; Smith and Smith, 2011; Jung et al., 2012; Pieterse et al., 2009, 2014).

The hormonal reprogramming underlying MIR drives pathogen-specific defense responses. JA- and ethylene-dependent pathways predominantly confer resistance against necrotrophic organisms and chewing insects, and, to a lesser extent, hemibiotrophic pathogens (Heidel and Baldwin, 2004; Pozo and Azcón-Aguilar, 2007; Pieterse et al., 2014). These pathways are characterized by the upregulation of lipoxygenase D gene (LOXD) and allene oxide cyclase gene (AOC); increased activities of polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), and β-1,3-glucanase; and the accumulation of phenolic compounds, PR1a, callose, and pectin at the sites of pathogen penetration (Jaiti et al., 2008; Wang et al., 2022). In contrast, SA-dependent defense responses, which are primarily effective against hemibiotrophic and biotrophic pathogens, are characterized by the accumulation of pathogenesis-related (PR) proteins, production of ROS, reinforcement of the cell wall via the enhanced deposition of callose and phenolic compounds, and activation of the phenylpropanoid pathway (Volpin et al., 1994; Fester and Hause, 2005; Song et al., 2015). Field and greenhouse studies have confirmed that AMF suppress both soil-borne and foliar pathogens in tomato plants, and exert synergistic effects when combined with rhizospheric microbes such as Trichoderma, Pseudomonas, and Bacillus spp. (Harrier and Watson, 2004; Umer et al., 2025). This suppressive effect is attributed to the enhanced secretion of antimicrobial compounds, coordinated activation of defense pathways, and restructuring of the rhizospheric microbiome, which collectively create a pathogen-suppressive environment (Farhaoui et al., 2025; Umer et al., 2025). Specifically, Funneliformis mosseae induces systemic resistance in tomatoes, reducing infections caused by Meloidogyne incognita (root-knot nematode) and Pratylenchus penetrans (root-lesion nematode) by 45 and 87%, respectively, even when the AMF and nematodes colonize spatially distinct root zones. This effect is mediated via the activation of the JA pathway and enhanced root structure and biochemical resistance (Vos et al., 2012). Furthermore, Rhizophagus intraradices (syn. Glomus intraradices) alleviates damage to plant roots caused by Nacobbus aberrans (false root-knot nematode) by reducing gall formation and suppressing nematode reproduction, with maximal efficacy observed under preventive inoculation regimes (Lax et al., 2011). Additionally, inoculation with AMF mitigates bacterial wilt caused by Ralstonia solanacearum by 65.7% through modulation of soil pH, enhancement of root phenolic content, and activation of leaf defense-related enzymes, including PPO and POD, thereby limiting yield loss during tomato fruit maturation (Li et al., 2021). AMF also prime JA-dependent defense responses, thereby reducing the severity of Alternaria solani, which causes early blight in tomato plants. AMF-primed plants exhibit the rapid activation of PAL, lipoxygenase (LOX), chitinase, and β-1,3-glucanase, along with the upregulation of PR genes, including PR1, PR2, and PR3, upon pathogen challenge (Song et al., 2015). Furthermore, Rhizophagus irregularis has been shown to mitigate damage caused by Botrytis cinerea, the causative agent of gray mold in tomato, through ISR, demonstrating sustained biocontrol efficacy when integrated into microbial consortia (Minchev et al., 2021). Additionally, Glomus spp. suppress Fusarium oxysporum f. sp. lycopersici, the causal agent of Fusarium wilt, while enhancing the growth of tomato plants; uptake of nutrients, including nitrogen, phosphorus, and potassium; chlorophyll content; and fruit yield under pot culture conditions (Kumari and Prabina, 2019; Kumari et al., 2019).

Collectively, these multifaceted mechanisms—direct pathogen competition, induction of systemic defense, and the promotion of beneficial soil–plant interactions—position AMF as a sustainable and eco-friendly alternative to synthetic phytosanitary products for the management of diverse pests and pathogens in tomato cultivation. However, the translational efficacy of the benefits observed in the laboratory is tempered by AMF-specific and environmental factors under field conditions.

4.3. Synergistic mechanisms underlying AMF-mediated alleviation of drought stress in tomato

Drought is a significant abiotic stressor that severely inhibits the growth of tomato plants by disrupting nutrient absorption, diminishing physiological efficiency, and ultimately reducing yield. To mitigate these adverse effects, integrated management strategies are essential, with AMF representing a promising biological approach. AMF exert multifaceted regulatory effects on tomato plants, effectively alleviating drought stress through the coordinated modulation of physiological metabolism, molecular regulation, nutrient uptake, and hormonal balance (Augé, 2001; Augé et al., 2015). Different species and strains of AMF exhibit species-specific regulatory characteristics, with ABA serving as a key signaling molecule in mediating the symbiotic relationship between AMF and host plants and playing a central role in regulating stress resistance (Herrera-Medina et al., 2007; Martín-Rodríguez et al., 2010; Xu et al., 2018). Specifically, plant–AMF symbiosis mitigates drought stress in tomato plants by reshaping the molecular expression profile, optimizing physiological responses, and regulating hormonal homeostasis, with these responses closely associated with the ABA synthesis capacity and AMF species specificity of the host (Chitarra et al., 2016; Xu et al., 2018).

Inoculation with AMF upregulates the expression of 14–3-3 genes TFT2 and TFT3, thereby reducing transpiration and enhancing WUE in wild-type tomato under drought conditions. In contrast, AMF specifically induce the expression of TFT5, TFT7, TFT9, and TFT10 in ABA-deficient mutants, thereby modulating transpiration responses to mitigate the decline in WUE (Xu et al., 2018). Moreover, ABA plays an essential role in the establishment and maintenance of functional plant–AMF symbiosis, as evidenced by the dependence of AMF colonization and symbiotic performance on the ABA biosynthetic capacity of the host plant (Aroca et al., 2008; Herrera-Medina et al., 2007; Martín-Rodríguez et al., 2010; Xu et al., 2018). Notably, ABA plays critical roles in both the initiation and maintenance of plant–AMF symbiosis, which in turn promotes the development and functional activity of the fungal symbiont (Aroca et al., 2008; Herrera-Medina et al., 2007; Martín-Rodríguez et al., 2010). For instance, various species of AMF, including Funneliformis mosseae and Rhizophagus intraradices, enhance drought tolerance in tomato by regulating Gs, modulating ABA content, and enhancing the activities of antioxidant enzymes (Chitarra et al., 2016), thereby further illustrating the synergistic interplay between AMF and ABA in mediating drought resistance.

Previous studies have demonstrated that AMF establish a stress-resistant regulatory network in which ABA, strigolactone, and JA serve as the core components (Chitarra et al., 2016; Ruiz-Lozano et al., 2016; Xu et al., 2015). These hormones act in concert to mediate plant–AMF symbiosis and enhance drought resistance in tomato. Under drought stress, tomato plants engaged in AMF symbiosis exhibit upregulation of the strigolactone synthesis gene SlCCD7, while SlCCD8 expression remains unchanged, resulting in elevated strigolactone levels that facilitate plant–AMF symbiosis. Root colonization by AMF exhibits a strong correlation with elevated strigolactone levels and the severity of drought stress (Ruiz-Lozano et al., 2016). Further research is necessary for confirming the intrinsic relationship between strigolactone biosynthesis and plant–AMF symbiosis under drought conditions. Colonization by AMF also upregulates the JA synthesis gene SlLOXD under both normal and drought conditions, contributing to the stabilization of the symbiotic relationship. Meanwhile, colonization by Septoglomus constrictum downregulates the ABA synthetic gene SlNCED under drought conditions, thereby maintaining higher Gs and plant water status. This coordinated regulation, involving the simultaneous enhancement of JA levels and suppression of ABA synthesis, contributes to maintaining the balance between symbiotic stability and plant water retention (Xu et al., 2015). Additionally, certain AMF species increase the levels of ABA glucosyl ester (ABA-GE) in roots, which serve as a reserve pool for rapid production of active ABA under stress and further reinforce the central regulatory role of ABA in the AMF–tomato symbiotic drought-resistance system (Chitarra et al., 2016; Rivero et al., 2018).

AMF play a crucial role in activating the plant antioxidant system, thereby mitigating drought-induced oxidative damage—a key physiological mechanism for protecting the symbiotic system and maintaining normal plant metabolism. Specifically, Funneliformis mosseae and Rhizophagus intraradices enhance the activity of key antioxidant enzymes, including SOD, ascorbate peroxidase (APX), and POD (Chitarra et al., 2016). Additionally, Septoglomus constrictum reduces lipid peroxidation and the accumulation of hydrogen peroxide (H₂O₂) under drought stress, while simultaneously increasing the activities of antioxidant enzymes (Duc et al., 2018). Furthermore, three glutathione S-transferases (GSTs) in Rhizophagus intraradices are upregulated under drought conditions, thereby enhancing oxidative stress defense mechanisms in both the fungal symbiont and its host plant. This regulation is essential for ensuring the proper development of arbuscules and the maintenance of functional nutrient transport (Balestrini et al., 2019; Xu et al., 2015).

AMF modulate Gs and coordinately regulate the expression of plant and fungal aquaporin (AQP) genes, thereby enhancing root hydraulic conductivity. This not only enhances the water absorption capacity of the host plant but also establishes a foundation for maintaining stable photosynthetic efficiency (Davies Jr et al., 1996; Augé et al., 2015; Chitarra et al., 2016). Under drought conditions, AMF upregulate specific plant AQP genes, such as LeNIP3;1, and fungal AQP genes, including RiAQPF2, while also modulating the expression of other genes, such as LePIP1;1 and LeTIP2;3 (Chitarra et al., 2016). The external hyphae of AMF can penetrate soil pores that are inaccessible to plant roots, thereby expanding the water absorption range and enhancing root hydraulic conductivity. The enhanced development of extraradical hyphae is crucial for mitigating drought stress in tomato plants (Davies Jr et al., 1996; Augé et al., 2015). Notably, the enhancement of root hydraulic conductivity facilitates the transmission of hydraulic signals from the roots to the above-ground tissues of the host plant, as evidenced by the maintenance of high Gs levels (Rodríguez et al., 1997).

Colonization by AMF significantly enhances the growth and nutrient acquisition efficiency of tomato plants under drought stress. The growth-promoting effects of AMF are species-specific and are closely associated with the regulation of carbohydrate allocation and nutrient transport genes (Dell'Amico et al., 2002; Berruti et al., 2013; Rivero et al., 2015; Duc et al., 2018; Xu et al., 2018). Specifically, AMF substantially increase the dry biomass, shoot biomass, and leaf surface area of drought-stressed tomato seedlings. For instance, Glomus clarum is particularly effective in promoting shoot biomass accumulation by facilitating the preferential allocation of a greater proportion of carbohydrates to the shoots (Dell'Amico et al., 2002; Rivero et al., 2015). In contrast, inoculation with Septoglomus constrictum increases the root and shoot dry weight of tomato plants by 14–18% compared to that of non-colonized plants under water stress (Duc et al., 2018). Furthermore, wild-type tomato plants exhibit a higher mycorrhizal colonization rate than mutant varieties under drought stress (Xu et al., 2018). Both single and mixed AMF inocula exhibit varying regulatory effects on tomato traits, whereas indigenous AMF isolates generally exert more pronounced growth-promoting effects, likely due to their adaptation to local environmental conditions (Berruti et al., 2013, 2016; Mannino et al., 2020).

The enhancement of nutrient acquisition efficiency by AMF further synergistically improves drought resistance in tomato, as the adequate availability of nutrients is crucial for maintaining plant physiological functions under stress. AMF significantly increase the uptake of nitrogen, phosphorus, calcium, magnesium, iron, and other essential nutrients in drought-stressed tomato plants (Subramanian et al., 2006; Chitarra et al., 2016; Volpe et al., 2018; Xu et al., 2018). Rhizophagus intraradices increases shoot phosphorus concentration in wild-type tomato plants by 23% under drought conditions, compared to a 14% increase under well-watered conditions (Xu et al., 2018). Rhizophagus intraradices also optimizes nitrogen uptake by modulating the mobility of nitrate (NO₃⁻) ions under conditions of water deficiency (Subramanian et al., 2006). The symbiotic inorganic phosphate (Pi) uptake pathway is central to AMF-mediated phosphorus transport (Bucher, 2007; Javot et al., 2007; Smith and Smith, 2011), with eight genes in the PHT1 family mediating Pi uptake by tomato roots (Chen et al., 2014). These PHT1 genes are induced by mycorrhizal colonization (Nagy et al., 2005, 2009). The LePT4 and LePT5 genes are upregulated under drought stress, exhibiting the highest expression levels in plants colonized by Funneliformis mosseae. Conversely, LePT3 does not participate in the drought stress response, whereas LePT1 and LePT2 exhibit opposing expression patterns. LePT2 and LePT4 play significant roles in enhancing drought tolerance by promoting the absorption of Pi and contributing to the synthesis of photosynthetic pigments and antioxidant enzymes (Volpe et al., 2018).

In response to drought conditions, the cytochrome P450 genes are upregulated in tomato roots colonized by Rhizophagus intraradices, thereby facilitating sterol synthesis, which is essential for arbuscule formation and supports the proper development of the symbiotic system and nutrient transport functions (Handa et al., 2015; Balestrini et al., 2019). Additionally, the fungal genes associated with the ‘conidiation protein 6’ domain and signal transduction-related domains in Rhizophagus intraradices are upregulated under drought stress. Fungal conidiation can be induced by nutrient deprivation or the desiccation of mycelia, aiding AMF in adapting to drought stress, maintaining symbiotic stability with tomato plants, and sustaining regulatory effects (Balestrini et al., 2019).

AMF symbiosis enhances the photosynthetic efficiency of tomato plants under stress by optimizing the photosynthetic apparatus, gas exchange parameters, and WUE, thereby providing a direct physiological basis for mitigating stress-induced reductions in yield (Dell'Amico et al., 2002; Subramanian et al., 2006; Chitarra et al., 2016; Ruiz-Lozano et al., 2016). Furthermore, this process is closely linked to enhanced water and nutrient availability mediated by AMF. Colonization by AMF preserves the normal functioning of photosystem II (PS II) during drought stress, with Septoglomus constrictum significantly increasing the Fv/Fm ratio in tomato plants (Duc et al., 2018). Plants inoculated with AMF exhibit no significant decline in photosynthetic rate (Pn) under drought conditions, contrasting sharply with the marked reductions observed in non-inoculated plants (Xu et al., 2018). Under field conditions, AMF-inoculated tomatoes maintain higher leaf relative water content (RWC), which provides a robust foundation for stable photosynthesis (Subramanian et al., 2006). As aforementioned, AMF enhances Gs in tomato plants under drought stress, with Septoglomus constrictum increasing Gs by 200% (Duc et al., 2018). This enhancement increases intracellular CO₂ concentration and promotes photosynthetic activity (Dell'Amico et al., 2002). The Pn and transpiration rate (Tr) of AMF-inoculated plants are adaptively regulated under stress, with Rhizophagus intraradices increasing Tr in ABA mutant plants under well-watered conditions and improving WUE in wild-type plants under drought stress (Xu et al., 2018).

AMF significantly reduce transpiration loss and optimize water allocation in wild-type tomato plants, while modulating transpiration responses in ABA-deficient mutants to maintain WUE (Xu et al., 2018). The enhanced nutritional status, particularly phosphorus accumulation, together with improved water status in colonized plants, synergistically contribute to increased WUE. This synergistic effect is the primary reason underlying the consistently higher fruit yield in AMF-inoculated tomato plants across varying drought intensities (Chitarra et al., 2016). Furthermore, the increased Gs and root hydraulic conductivity observed in AMF-colonized plants correlate with enhanced water uptake by the roots. Notably, the recovery of non-inoculated plants under fully watered conditions does not restore the Pn and Gs, thereby confirming that AMF exert a stable and long-term regulatory effect on the photosynthetic system of tomato plants (Dell'Amico et al., 2002).

4.4. AMF-mediated amelioration of salt stress in tomato plants

Soil salinization is a significant agricultural and eco-environmental challenge, particularly in arid and semi-arid regions worldwide, where it severely limits plant growth. Salinity reduces soil water potential and promotes the accumulation of toxic ions such as Na⁺ and Cl⁻, leading to water deficits, nutritional imbalances, and ion toxicity in plants, thereby disrupting nutrient uptake, osmotic regulation, and cellular functions (van Zelm et al., 2020). High salinity critically impairs seed germination, vegetative growth, fruit yield, and overall quality in tomato plants (Yurtseven et al., 2005; Roșca et al., 2023). AMF are obligate biotrophs belonging to the phylum Glomeromycota and establish mutualistic symbioses with most flowering plants. AMF–plant symbiosis has emerged as an environmentally friendly strategy to mitigate salt stress in tomato plants, particularly when combined with compost application (Hajiboland et al., 2010; Abdel Latef and Chaoxing, 2011a; Mekkaoui et al., 2024).

AMF mitigate salt stress through various interconnected mechanisms, beginning with their role in promoting growth and nutrient uptake in tomato plants. Salt stress markedly diminishes dry matter accumulation in the roots, stems, and leaves, as well as leaf area and the fresh and dry weights of shoots and roots, primarily due to osmotic stress and ion-specific toxicity from Na⁺ and Cl⁻ (Hajiboland et al., 2010; Tanveer et al., 2020). Inoculation with AMF effectively counteracts these growth inhibitions, exerting a more pronounced positive effect on above-ground biomass, attributable to the preferential allocation of carbohydrates toward root colonization (Abdel Latef and Chaoxing, 2011b). For instance, colonization by Funneliformis mosseae has been shown to enhance dry matter content and leaf area, while Rhizophagus intraradices is particularly beneficial for salt-tolerant cultivars such as Piazar, compared with salt-sensitive varieties like Behta (Hajiboland et al., 2010; Abdel Latef and Chaoxing, 2011a). AMF-inoculated seedlings exhibit a higher accumulation of dry matter in saline soils (0.098 g plant⁻¹) compared to that in non-inoculated counterparts (0.082 g plant⁻¹) (Balliu et al., 2015). Through extensive extraradical hyphal networks, AMF expand nutrient absorption ranges, enhancing the uptake of nitrogen, phosphorus, potassium, calcium, magnesium, iron, manganese, and zinc, while simultaneously reducing Na⁺ accumulation in fruits (Ebrahim and Saleem, 2017; Kong et al., 2020). Phosphorus nutrition is particularly crucial, as AMF facilitate phosphorus uptake via vacuolar membrane integration and Na⁺ compartmentalization, even under low-phosphorus conditions (Cantrell and Linderman, 2001). Furthermore, AMF promote the accumulation of osmotic regulators, including soluble sugars, proline, betaine, and polyamines, which help maintain cellular osmotic balance in salt-stressed plants (Evelin et al., 2009; Kong et al., 2020). Additionally, co-inoculation with Rhizophagus clarum and Rhizophagus intraradices enhances fruit quality by increasing the contents of vitamin C, soluble sugar, and lycopene, as well as single-fruit weight and yield per plant (Evelin et al., 2009; Kong et al., 2020; Chandrasekaran et al., 2021).

Another key mechanism for maintaining ionic homeostasis is the regulation of ion balance, which is crucial for plant growth under salt stress. Ion imbalance, resulting from competition between Na⁺/Cl⁻ and essential nutrients, significantly constrains the growth of tomato plants (Dasgan et al., 2002). AMF play a vital role in regulating ion uptake and transport, with the K⁺/Na⁺ ratio serving as a key indicator of salt tolerance (Hajiboland et al., 2010). AMF restrict the translocation of Na⁺ from the roots to shoots, thereby increasing the K⁺/Na⁺, Ca²⁺/Na⁺, and Mg²⁺/Na⁺ ratios in the leaves and stems, which protects the photosynthetic organs (Hajiboland et al., 2010; Santander et al., 2019). Mycorrhizal plants, particularly those colonized by Funneliformis mosseae, consistently exhibit higher K⁺ and lower Na⁺ levels across varying salinity gradients (Abdel Latef and Chaoxing, 2011a). Furthermore, salt-adapted Rhizophagus etunicatum has been shown to be more effective in reducing leaf Na⁺ levels compared to Funneliformis mosseae and Rhizoglomus irregulare (Rivero et al., 2018). A high K⁺/Na⁺ ratio is essential for maintaining cytoplasmic balance, promoting Na⁺ efflux, and preventing disruptions in metabolic processes and protein synthesis (Hajiboland et al., 2010; Augé et al., 2015). AMF also regulate the expression of AQP genes such as GintAQP1 in Rhizophagus intraradices, as well as Na⁺/H⁺ antiporter genes such as LeNHX1 and LeNHX2, to maintain ionic homeostasis (Ouziad et al., 2006).

Inoculation with AMF has been shown to enhance the photosynthetic capacity and water status in salt-stressed tomatoes (Chandrasekaran et al., 2021). Salt stress induces stomatal closure, reduces the chlorophyll content, and inhibits the assimilation of CO₂, thereby impairing the photosynthetic efficiency (Lin et al., 2017). However, inoculation with AMF mitigates these adverse effects by enhancing the concentration of chlorophyll, net Pn, Gs, and Tr, while simultaneously promoting the assimilation of CO₂ (Abdel Latef and Chaoxing, 2011a; Chandrasekaran et al., 2019). For instance, plants inoculated with Rhizophagus intraradices exhibit higher Tr and Gs, whereas Rhizophagus fasciculatus enhances chlorophyll synthesis by increasing leaf nitrogen and magnesium content and reducing sodium uptake (Ebrahim and Saleem, 2017; Kong et al., 2020). An elevated chlorophyll a/b ratio indicates enhanced light-harvesting efficiency and improved salt adaptation (Ebrahim and Saleem, 2017). Inoculation with AMF also increases root hydraulic conductivity and improves water absorption through hyphal networks that penetrate soil pores inaccessible to plant roots (Augé et al., 2015; Ruiz-Lozano et al., 2016). Although inoculation with AMF may reduce WUE owing to increased transpiration, improvements in water uptake and photosynthetic performance collectively contribute to enhanced plant growth (Kong et al., 2020). Additionally, the AMF-induced accumulation of JA in roots—particularly in Rhizophagus etunicatum-colonized plants—serves as a bio-protector, while metabolites such ABA-GE and β-ionone further regulate water balance and stress responses (Rivero et al., 2018).

AMF enhance the activity of the antioxidant system, thereby alleviating oxidative stress. Salt stress induces the production of ROS, including superoxide radicals (O₂⁻), H₂O₂, and hydroxyl radicals (OH⁻), which can damage proteins, nucleic acids, and lipids, ultimately disrupting membrane integrity (Apel and Hirt, 2004). Inoculation with AMF enhances the activity of ROS-scavenging enzymes, including SOD, POD, APX, and CAT (He et al., 2007; Abdel Latef and Chaoxing, 2011a). For instance, tomatoes inoculated with Funneliformis mosseae exhibit increased enzyme activities (except for SOD and CAT at 100 mM NaCl) and reduced levels of H₂O₂ and malondialdehyde (MDA), both of which serve as indicators of reduced lipid peroxidation and membrane damage (Abdel Latef and Chaoxing, 2011a). Furthermore, AMF colonization promotes the accumulation of proline, a non-enzymatic antioxidant that scavenges ROS and stabilizes cellular structures (Hajiboland et al., 2010). The lower MDA content and reduced membrane leakage observed in inoculated plants further corroborate the protective role of the antioxidant system (Al-Karaki et al., 2001). Collectively, these mechanisms position AMF as a promising biostimulant for enhancing tomato productivity in saline soils, thereby contributing to more resilient and sustainable agricultural systems.

5. Synergistic interactions between AMF and PGPR: mechanisms and agronomic implications

5.1. Mechanistic foundations of AMF-PGPR co-inoculation

The co-inoculation of AMF and PGPR typically results in synergistic effects that exceed the benefits conferred by single inoculations. This synergy is often mediated by the PGPR-induced enhancement of AMF colonization, which in turn amplifies plant growth and nutrient acquisition (Alam et al., 2011; Wilkes et al., 2020; Savastano and Bais, 2024) (Figure 4). For instance, inoculation with Bacillus subtilis was found to significantly increase root colonization by Funneliformis mosseae in rose-scented geranium (Pelargonium graveolens), leading to increased shoot biomass and improved nutrient uptake compared to those observed in single inoculations or uninoculated controls (Alam et al., 2011). Similarly, another study reported that Bacillus subtilis promoted the colonization of onion (Allium cepa) by Rhizophagus irregularis, which correlated with increased plant biomass and enhanced nutrient acquisition (Toro et al., 1997). Studies on winter wheat have further demonstrated that dual inoculation with Bacillus amyloliquefaciens and Rhizophagus intraradices increased the number of arbuscules and the production of glomalin—a glycoprotein associated with AMF biomass and soil aggregation—indicating that PGPR exert a stimulatory effect on AMF development (Wilkes et al., 2020). However, the relationship between AMF and PGPR is not universally linear or predictable. A meta-analysis revealed that while dual inoculation consistently improves plant performance, the application of PGPR does not invariably enhance AMF colonization. This finding suggests that alternative mechanisms, including the direct promotion of plant growth by PGPR, modulation of root exudates, or activation of ISR, may also contribute to the observed synergistic effects (Primieri et al., 2022). There are significant knowledge gaps regarding the species-specific interactions between AMF and PGPR, the influence of soil nutrient status on these tripartite associations, and the optimal timing of inoculation for maximizing their benefits (Gopal et al., 2012; Primieri et al., 2022).

Figure 4.

Synergistic mechanisms of PGPR and AMF in enhancing tomato growth and stress resilience. (1) PGPR increases the availability of soil nutrients, while AMF facilitates the transport of PGPR and the mobilized nutrients through its mycelial network to the roots. Together, these partners synergistically promote the uptake of essential nutrients, including nitrogen (N), phosphorus (P), and potassium (K). (2) The hyphal networks formed by AMF bridge soil pores, thereby enhancing water availability and improving photosynthetic efficiency. (3) Ion homeostasis is maintained through the efflux of sodium ions (Na⁺) and the retention of potassium ions (K⁺), collectively sustaining cellular osmotic balance. (4) Antioxidant enzymes, such as superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), are crucial in scavenging reactive oxygen species (ROS) to mitigate oxidative damage. (5) The production of antibiotics and lipopeptides, along with the activation of induced systemic resistance (ISR) mechanisms—including polyphenol oxidase (PPO) and lignin biosynthesis—confers biotic resistance against pathogens.

5.2. Alleviation of abiotic stress through AMF-PGPR cooperation

Abiotic stressors, particularly drought and salinity, significantly restrict plant growth and productivity. The combined application of AMF and PGPR has been shown to be particularly effective in enhancing plant tolerance to these stressors, as their synergistic interactions amplify the beneficial effects beyond those achieved by individual inoculants. PGPR can stimulate the growth and activity of AMF under conditions of water limitation, thereby enhancing the water and nutrient scavenging capacity of the mycorrhizal hyphal network. This synergy results in improved plant physiological status and enhanced drought resilience across various species. For instance, co-inoculation of Bacillus sp. with Funneliformis mosseae and Rhizophagus irregularis was found to mitigate drought stress in lettuce (Lactuca sativa) by increasing the colonization of AMF and improving plant water status (Vivas et al., 2003). This co-inoculation also enhanced multiple physiological parameters, including nutrient uptake (particularly nitrogen, phosphorus, and potassium), photosynthetic activity, and Gs, while reducing oxidative damage through the upregulation of antioxidant enzymes (Marulanda et al., 2006; Anli et al., 2020; Begum et al., 2022). The combined application of Glomus versiforme and Bacillus methylotrophicus not only promoted nutrient uptake in tobacco (Nicotiana tabacum), but also increased the activities of antioxidant enzymes, resulting in reduced oxidative stress and increased biomass under drought conditions (Begum et al., 2022). A study on date palms demonstrated that co-inoculation with AMF and PGPR significantly improved nitrogen and phosphorus acquisition, enhanced Gs, and promoted superior morphological traits. These improvements were attributed to the extended AMF hyphal network that facilitated water uptake from the deeper soil layers (Anli et al., 2020). Similarly, the co-inoculation of Rhizophagus irregularis and Bacillus thuringiensis enhanced water uptake in Retama sphaerocarpa through hyphal-mediated water transport (Marulanda et al., 2006). Despite these advancements, the molecular interactions among plants, AMF, and PGPR under drought stress remain largely unexplored (Nanjundappa et al., 2019).

The co-inoculation of AMF and PGPR significantly enhances plant salt tolerance and growth, with tomato serving as a representative model crop in such studies. AMF establish mutualistic associations with plant roots, thereby facilitating the absorption of nutrients, particularly phosphorus, through their extensive hyphal networks. Additionally, AMF improve water retention and soil structure, thereby enhancing plant resilience under saline conditions (Wang et al., 2023; Boyno et al., 2025). In parallel, PGPR support plant growth through phytohormone production, nitrogen fixation, and nutrient solubilization, which collectively promote growth and enhance stress tolerance (Mhlongo et al., 2020). Furthermore, AMF and PGPR interact synergistically to enhance plant osmotic adjustment by promoting the accumulation of proline and soluble sugars. They also jointly activate antioxidant enzyme systems, including SOD, POD, and CAT, to scavenge ROS and mitigate membrane lipid peroxidation (Zhou X. et al., 2022; Bilgili and Bilgili, 2023). AMF and PGPR also co-regulate the expression of ion transport proteins, including high-affinity potassium transporters (HKT) and sodium/hydrogen exchangers (NHX), as well as genes in the salt overly sensitive (SOS) signaling pathway. This coordinated regulation facilitates sodium (Na⁺) efflux and vacuolar compartmentalization, thereby maintaining the intracellular potassium (K⁺)/sodium (Na⁺) balance (Reginato et al., 2021; Chen et al., 2022).

The co-inoculation of PGPR, specifically Pseudomonas putida and Azotobacter chroococcum, with AMF, such as Glomus mosseae, significantly enhances both stem and root dry weights in tomato plants, as well as the uptake of essential nutrients, including phosphorus, magnesium, potassium, and calcium. Notably, their combined application exerts the most pronounced effect on phosphorus content (Zare et al., 2011). Similarly, the co-inoculation of Funneliformis mosseae (AMF) and Bacillus subtilis (PGPR) alleviates low-salinity stress by strengthening the antioxidant defense system and osmotic adjustments. Here, AMF primarily facilitated the accumulation of osmolytes, whereas PGPR enhanced the total antioxidant capacity, and their synergistic effect increased fruit yield (Zhou X. et al., 2022). Additionally, combined applications of AMF and PGPR, either alone or in conjunction with compost, have been reported to be more effective in alleviating water stress in tomatoes than single biofertilizer treatments. This subsequently increases the activities of antioxidant enzymes in the shoot, improves chlorophyll fluorescence, and enhances the contents of fruit sugar and protein, even under drought conditions (Tahiri et al., 2022). The ecological interactions between AMF and PGPR in the rhizosphere and hyphosphere further underscore their synergistic effects, as the ERM of AMF serves as a conduit for the colonization and dispersal of PGPR, thereby facilitating access to nutrient-rich niches and enhancing the bioavailability of immobilized nutrients, such as organic phosphorus (El-Sawah et al., 2021; Jiang et al., 2021). In turn, PGPR-derived exopolysaccharides improve soil structure, form protective biofilms around roots to mitigate Na⁺ influx, and potentially stimulate the colonization of AMF through signaling interactions (Kong et al., 2020; Qin et al., 2024).

5.3. Enhanced biotic stress resistance via AMF-PGPR consortia

The co-inoculation of AMF and plant PGPR enhances plant defense mechanisms against pathogens, producing a synergistic effect that is more effective that of individual inoculants. Both microbial groups can directly antagonize pathogens and/or induce systemic resistance in host plants (Lowe et al., 2012), with AMF competing with soil-borne pathogens for root colonization sites and nutrients. For instance, Glomus spp. can decrease infection by the white rot fungus Sclerotium rolfsii in common beans through resource competition. Additionally, PGPR such as Bacillus subtilis produce antimicrobial compounds, including lipopeptides and antibiotics, which directly inhibit the growth of pathogens, as evidenced in the same pathosystem (Mohamed et al., 2019).

Moreover, co-inoculation with AMF and PGPR can enhance intrinsic defense mechanisms in the host plant. For instance, the co-application of Glomus spp. and Bacillus subtilis in common beans has been shown to synergistically increase the activity of defense-related enzymes, such as POD and PPO, which are essential for lignin biosynthesis and ROS scavenging (Mohamed et al., 2019). Plant-associated PGPR may also enhance phosphorus availability to plants, thereby supporting both growth and defense during pathogen challenges (Kohler et al., 2007). Notably, although PGPR often promote AMF colonization (Savastano and Bais, 2024), this does not necessarily correlate with improved pathogen resistance. For instance, challenge with Aspergillus niger increased the colonization of lettuce by Rhizophagus irregularis following co-inoculation with Bacillus subtilis; however, this did not result in stronger disease suppression. This suggests the involvement of additional interaction mechanisms, such as the priming of plant immune responses or alterations in the composition of the rhizospheric microbiome (Kohler et al., 2007), necessitating a deeper understanding of microbe–microbe and microbe–plant signaling under pathogen stress (Niu et al., 2020). Although current research often emphasizes the roles of individual microorganisms, the synergistic effects arising from multi-level interactions between AMF and PGPR offer greater potential for enhancing plant stress resistance and productivity. Future efforts should focus on constructing functionally complementary synthetic microbial communities and integrating molecular breeding approaches with the development of targeted microbial agents to provide effective strategies for the green and sustainable development of agriculture, particularly in saline-alkali regions.

6. Conclusions and future prospects

The escalating challenges posed by climate change and intensive agricultural practices underscore the need to develop sustainable strategies for maintaining and enhancing tomato productivity. This review provides a comprehensive examination of the multifaceted roles of PGPR and AMF in alleviating both biotic and abiotic stresses in tomato cultivation (Figure 4). These beneficial rhizospheric microorganisms represent a promising biological alternative to conventional chemical inputs, providing the dual benefits of stress mitigation and growth promotion through interconnected physiological, molecular, and ecological mechanisms. PGPR enhance stress tolerance in tomato plants through diverse direct and indirect mechanisms, including biological nitrogen fixation, solubilization of phosphorus and potassium, siderophore-mediated iron acquisition, and the production of phytohormones—particularly auxins, gibberellins, and cytokinins. These bacteria also activate ISR, reinforce cell wall structures by inducing the deposition of lignin and callose, enhance the activities of antioxidant enzymes such as SOD, CAT, and POD, and promote the accumulation of osmoprotectants such as proline and glycine betaine. Concurrently, AMF establish mutualistic symbioses with the roots of tomato plants, extending hyphal networks that enhance the uptake of water and nutrients, particularly phosphorus and nitrogen. AMF also modulate hormonal signaling networks involving ABA, JA, and strigolactones, activate MIR, regulate the expression of AQP genes to enhance root hydraulic conductivity, and improve photosynthetic efficiency and WUE under stress conditions.

The synergistic interactions between PGPR and AMF consistently surpass the effects of single inoculations. These microbial partners occupy complementary ecological niches and engage in mutualistic exchanges that enhance their respective functions. PGPR can stimulate spore germination and hyphal development in AMF, whereas AMF hyphae facilitate the colonization and dispersal of PGPR within the soil matrix. This cooperation enhances nutrient acquisition, stress tolerance, and pathogen suppression through multiple mechanisms, including improved antioxidant defense, enhanced osmotic adjustment, and coordinated regulation of ion transporters, including HKT, NHX, and the SOS pathway, as well as the establishment of disease-suppressive rhizospheric microbiomes. Despite substantial progress in understanding plant–microbe interactions, several critical knowledge gaps and challenges remain, warranting further investigation, as discussed hereafter. First, the molecular signaling networks underlying tripartite interactions among tomato plants, PGPR, and AMF under stress conditions remain poorly characterized. Although individual signaling pathways involving phytohormones, ROS, and calcium fluxes have been identified, their integration and cross-talk during combined biotic and abiotic stress episodes require systematic investigation. The integration of advanced omics approaches—including transcriptomics, metabolomics, and proteomics—with spatial analysis techniques could elucidate the temporal and spatial dynamics of these signaling networks.

The translation of laboratory and greenhouse findings to field conditions remains inconsistent, largely due to the complexity of natural soil ecosystems and competition from indigenous microbial communities. Future research should focus on understanding the ecological determinants of inoculant establishment and persistence, including soil organic matter content, pH, nutrient availability, and structure of the resident microbial community. The development of effective formulations and delivery systems that protect microbial viability during storage and following soil application represents a major technological bottleneck, requiring innovative solutions. The integrated application of AMF and PGPR alongside emerging agricultural technologies offers unexplored synergies. The combination of microbial inoculants with precision agriculture tools, including sensor-based monitoring of soil and plant health, could facilitate site-specific and temporally optimized inoculation strategies. Furthermore, the integration of microbiome engineering with genome editing technologies, such as CRISPR-Cas systems, presents opportunities for enhancing beneficial plant–microbe interactions by modifying plant genes involved in symbiotic signaling and nutrient exchange. The development of customized microbial consortia tailored to specific stress scenarios and tomato varieties represents a priority research direction. Unlike single-strain inoculants, synthetic microbial communities can leverage functional complementarity and emergent properties to deliver robust stress protection across diverse environmental conditions. High-throughput screening platforms, coupled with machine learning algorithms, could further accelerate the identification of optimal microbial combinations and their dose–response relationships.

In conclusion, PGPR and AMF represent powerful tools for the sustainable production of tomato under increasing environmental stress. The synergistic potential of these beneficial microorganisms, when effectively harnessed through integrated management strategies, offers a viable strategy for reducing chemical inputs while maintaining or enhancing crop productivity. Achieving this potential will necessitate sustained interdisciplinary collaboration among plant biologists, microbiologists, soil scientists, agronomists, and agricultural engineers to translate mechanistic insights into practical solutions that benefit farmers, consumers, and the environment.

Funding Statement

The author(s) declared that financial support was received for this work and/or its publication. This work was supported by grants from the National Natural Science Foundation of China (grant number 32560077 and 32460457), the Yunnan Fundamental Research Projects (grant number 202501AU070172 and 202401AU070002), the Yunnan Provincial Department of Education Science Research Fund Project (grant number 2024J0939), the Special Basic Cooperative Research Innovation Programs of Qujing Science and Technology Bureau and Qujing Normal University (grant number KJLH2024ZD04), and the Program of Innovation Research Team from Qujing Normal University.

Author contributions

YS: Validation, Writing – original draft, Writing – review & editing, Formal analysis. HC: Validation, Writing – review & editing. RH: Writing – review & editing, Validation. WM: Validation, Writing – review & editing. QL: Writing – review & editing, Validation. ZL: Writing – review & editing, Validation. YG: Writing – review & editing, Validation. CL: Writing – review & editing, Writing – original draft, Funding acquisition, Validation.

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declared that Generative AI was not used in the creation of this manuscript.

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