Advanced Microbial Techniques in Agriculture, Environment, and Health Management

Advanced Microbial Techniques in Agriculture, Environment, and Health Management provides current perspectives on the fields of agriculture, the environment and health. This important reference presents recent advancements in applied microbial technology, compiling it in a comprehensive manner and transferring applied microbial technology from laboratory conditions to field level. In 20 chapters, the book focuses on microbial interventions for all-inclusive, cost-effective environmental management tactics while also linking the cumulative microbial services involved in the up-gradation of agriculture, environment and health.

In addition, the book offers detailed information on emerging environmental issues and proposes ways of controlling their consequences using different approaches to treatment.

• Provides conceptual information and recent advances in microbial services involved in enhancing environmental sustainability
• Offers potential solutions for a variety of problems like low agricultural productivity, emission of harmful contaminants from both natural and anthropogenic sources, and disease development in plants and humans
• Contains applied, in-depth knowledge on microbial contributions as bio-inoculants, enzymatic sources and antimicrobials

• Language: English
• Publisher: Academic Press
• Release date: Jan 30, 2023
• ISBN: 9780323916448

Book preview

Chapter 1

Beneficial microbes for sustainable agroecosystem

Sandhya Bind¹, Sudha Bind¹ and Dinesh Chandra¹,²,    ¹Department of Biological Sciences, College of Basic Sciences & Humanities, Govind Ballabh Pant University of Agriculture & Technology, U.S. Nagar, Uttarakhand, India,    ²GIC Chamtola, Almora, Uttarakhand, India

Abstract

According to the Food and Agricultural Organization (FAO), around one billion people are hungry, undernourished, and live without adequate daily calories. The effects of climate change on temperature, precipitation, and other factors are likely to diminish agricultural productivity. Farmers all over the world depend on chemical fertilizers to increase crop productivity. The disproportionate practice of chemical fertilizers, herbicides, and pesticides contribute to environmental pollution and adversely affect human and animal health. Microorganisms can be an attractive and eco-friendly substitute for synthetic fertilizers and can reduce the various types of strains in agricultural productivity. Microorganisms enhance the uptake of various nutrients such as nitrogen, phosphorus, potassium, calcium, zinc, iron, etc., as well as plant resistance toward abiotic and biotic stresses. Microorganisms are a solution for every problem related to agriculture. This chapter focuses on the role of beneficial microorganisms in the enhancement of crop productivity to achieve sustainable agriculture.

Keywords

Climate change; microorganisms; nutrients; agriculture; bioremediation

1.1 Introduction

According to the United Nations the world population will reach up to 9.8 billion by 2050 (Bongaarts, 2009). To nourish this ever-growing population, agricultural productivity has to be increased by 70%. Various strategies have been used to increase agricultural productivity. Conventional breeding negatively affects the physical, chemical, and biological properties of soil and carbon stocks, which makes them unsustainable for future food and fiber. The excessive manufacture and utilization of chemical fertilizers and pesticides are not sustainable. Production of synthetic nitrogen fertilizer is energy intensive. Potassium and phosphorus fertilizers are produced from mined resources, which are likely to deplete in 100 years. Excessive utilization of these chemical fertilizers and pesticides leads to environmental pollution and many health problems. Therefore an eco-friendly approach is needed for achieving global food security with sustainable agriculture.

According to FAOSTAT (2021), the agroecosystem comprises 40% of the land area that provides food, fiber, and biofuels to the growing world population. Enhanced productivity in these systems depends on intense agricultural management and practices that have an impact on the important functions and services of the ecosystem, including soil fertility, renewal, and purification of groundwater, and also suppression of pathogens and pests (Dornbush & von Haden, 2017). Past and current agricultural practices will not be sustainable for a long time. Thus there is a need for agricultural practices that lead to high agricultural production and sustainable establishment of agroecosystem services (Pe'er et al., 2019). In agriculture a multifaceted network of connections exists between plants and microbes. Ecologically compatible and eco-friendly techniques helpful in providing adequate nutrients to the ever-growing population through improved quality and quantity of agricultural products is necessary. The application of beneficial microbes in agriculture served as an eco-friendly approach under the current scenario of climate change. Agriculturally important microbes play a key role in nutrient management, disease, and pest management and act as a substitute for chemical fertilizers and improve the quality of crops. Anthropogenic activities and intensive agricultural practices enhance greenhouse gas production (Hunter, 2008). The soil microbial community plays a vital role in the consumption of greenhouse gases (Bardgett, Freeman, & Ostle, 2008). Recent research aims to exploit the traits of microbes in improving the nutrient content and crop protection against abiotic and biotic stresses with changing climate to achieve sustainable agriculture. This chapter is envisioned to emphasize the advent of the agriculturally important microorganism for the development of a model agricultural system through proficient use of nutrients and recycling of energy, preserving the resources of the natural ecosystem under changing climate.

1.2 Beneficial microbes in agriculture

The world of microbes is a huge unexplored reservoir on the earth. According to Bhattacharyya and Jha (2012), only a minute portion of approximately 10% of microbial diversity is identified up to the last century. Though microbes are the smallest entity among living organisms, they play a vibrant role in all ranges of activities inside the living organism on the planet. Therefore microbial ecology-based research has become an imperative frontline in biological sciences. The plant rhizosphere is a chief niche where abundant microorganisms are found. The microbes present in the rhizosphere are mostly beneficial. The utilization of these beneficial microbes in bioformulation serves as an efficient way of enhancing crop productivity. Among microbial diversity, bacteria, fungi, algae, actinomycetes, protozoa, and viruses have enormous activities (Andreote & Silva, 2017).

Plant body, considered as a multifaceted interplay of ecological niches that harbor a wide diversity of microorganisms in their rhizosphere, rhizoplane, phyllosphere, and endosphere, form a broad range of beneficial, harmful, and neutral interactions (Turner, James, & Poole, 2013). Plant root exudates are carbon-rich, having sugars, organic acids, vitamins, etc. Plants also release numerous compounds due to various biotic and abiotic stressors. Soil microbes (especially bacteria) can sense these chemical signals and secrete various compounds, activating the defense mechanism of plants (Glick, 2012). A native plant microbial community is known as a microbiome, which represents a group of various organisms that colonize a given environment (Boon et al., 2014). Microbiomes energetically interact with the plant host to establish a synergistic relationship, influencing the physiology of the host (Foo, Ling, Lee, & Chang, 2017; Sati et al., 2022). Plentiful studies have been conducted to explore the mechanism of microbiome development and its dynamics in shaping plant performance in the ecosystem. Microbes play an important and diverse role in agriculture, horticulture, and forestry. Agriculturally important microbes are huge groups of microbes that interact with plants and have beneficial effects (Higa & Parr, 1994). Various microbes play a significant role in plant growth and health promotion by increasing the disease resistance of plants against various plant pathogens, thereby helping in crop protection. According to Higa and Wididana (1991), effective microorganisms signify a group of beneficial microorganisms used efficiently as microbial inoculants for intensification of native microbial diversity in the rhizosphere and the bulk soil of growing plants. Microorganisms play a key role in the management of pests (invertebrates and vertebrates), weeds, and plant diseases that damage agricultural crops and forest plants. Fungi and bacteria play a key role in providing resistance toward various abiotic (drought, salinity, heat) and biotic (insect, pest, disease) stress (Chandra, Srivastava, Gupta, Franco, & Sharma, 2019b; Chandra et al., 2019a; Singh, Gill, & Tuteja, 2011). Viruses are seen to play a significant role even at extreme temperatures (up to 115°F), for instance, in Yellowstone National Park, where it forms a symbiotic association by colonizing plant roots (Roossinck, 2011). Due to their exceptionality—their impulsive nature and biosynthetic abilities—, microbes are relatively adaptable to specific environmental and cultural conditions that help in solving numerous problems related to disease suppression and crop improvement.

Microbes are an alternative to synthetic fertilizers and pesticides, and as such, they are extensively used as biofertilizers in natural farming and agricultural practices (Chandra, Srivastava, Glick, & Sharma, 2020). Belowground soil biota exhibits a vital role in the functioning of agroecosystems. Among these biotas the microbial community is the key element of both natural and managed agroecosystems (Fierer, 2017). Microbes associated with plants and soil help in nutrient cycling and carbon storage, maintaining the physical, chemical, and biological characteristics of the soil (Garnica, Rosenstein, & Schon, 2020). The microbial community of the soil enhances plant growth and improves plant health through direct and indirect mechanisms. Modern agricultural practices focus on high yield with a low number of plants, which negatively affects the plant-associated soil microbial community, which ultimately reduces soil quality (Banerjee et al., 2019; Mariotte et al., 2018). The use of these belowground microbial communities as a management strategy for the agricultural system is gradually being recognized and also plays a key element in meeting the challenges of sustainable agroecosystems (Barka et al., 2016; Ray, Lakshmanan, Labbé, & Craven, 2020). In the present day, more emphasis is given to the functional characteristic or diversity of crops as well as on the associated above- and belowground microbial community (Barot et al., 2017). A conceptual diagram demonstrating the role of beneficial microbes in sustainable agriculture is summarized in Fig. 1.l.

Figure 1.1 Schematic diagram depicting the role of beneficial microbes in sustainable agriculture.

1.3 Beneficial microbes: a key element for sustainable agricultural system

In the mid-20th century, agricultural technology that was used to ensure the green revolution earned high ecological costs, leading to various environmental problems, climate change, and destruction of biodiversity (Scherr & McNeely, 2008). Soil microbes produce different kinds of metabolites and maintain the physical, chemical, and biological characteristics of the soil, enhancing soil health and fertility. An ideal agricultural system should be regenerative, self-sustaining, protective of the environment, and economically valuable for both producers and consumers. Soil microbes produce various plant growth regulators. Among the beneficial microbes, bacteria are present in enormous amounts. Plant growth promoting rhizobacteria (PGPR) are beneficial bacteria that enhance plant growth by producing indole acetic acid (IAA), cytokinin, gibberellin, hydrocyanic acid (HCN), lytic enzyme, siderophore, antibiotic, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, solubilization of phosphate, and by nitrogen fixation (Chandra, Pallavi, & Sharma, 2017).

1.4 Rhizosphere: a hot spot of beneficial microbes

The rhizosphere represents the narrow zone of soil directly influenced by plant roots having a high turnover of nutrients and microbial density. It is the region where abiotic and biotic factors remain in strict control of each other (Hu et al., 2018). Beneficial microbes present in the rhizosphere in a high number include mycorrhizal fungi and PGPR (Sati et al., 2020). The variety and extent of organic nutrients in root exudates, root architecture, and root branching pattern determine the microbial diversity in the rhizosphere. The process of root exudation helps in the transfer of carbon into the soil. Up to 20% of fixed carbon is released into the soil through root exudates by photosynthesis.

1.4.1 Beneficial microbes

1.4.1.1 Plant growth promoting bacteria

PGPR represents a diverse group of bacteria, residing in the rhizosphere and enhancing the growth of plants through various direct and indirect mechanisms, thus showing a positive effect on the environment. In most cases, such plant growth promoting bacteria belong to the following species: Pseudomonas, Arthrobacter, Achrombactor, Enterobacter, Variovorax, Alcaligenes, Bacillus, Klebsiella, Burkholderia, Azospirillum, Azotobacter, and Serratia. The interaction between plants and PGPR is synergistic, with both partners benefitting from it. Plants provide carbohydrates, organic acids, vitamins, and minerals through root exudates. In turn, PGPR help in plant growth by enhancing nutrient availability through nitrogen fixation, solubilization of phosphate, zinc, potassium, chelation of iron, and some other micronutrients (such as zinc, boron, and copper). PGPR also produce various phytohormones (IAA, gibberellin, cytokinin, ethylene, and abscisic acid), ACC deaminase (reduces ethylene concentration during stress condition), HCN, lytic enzymes, and antibiotics, which act against various plant pathogens and also play a key role in induced systemic resistance of plants (Backer et al., 2018). PGPR also produces hydrolytic enzymes such as glucanases and pectinases, which hydrolyze the fungal cell wall and inhibit the growth of fungal pathogens. PGPR also provides resistance to different kinds of abiotic stresses (water stress, salinity, and cold stress due to enzymatic antioxidant properties e.g., Pseudomonas frederiksbergensis, Bacillus spp., and Planomicrobium spp.) (Abbas et al., 2019). PGPR have the ability to release various osmolytes that synergistically act with the osmolytes produced by plants and increase plant growth (Paul & Nair, 2008). According to the study by Ansary et al. (2012), inoculation of maize with Pseudomonas fluorescens increased the proline content under water stress conditions. Higher proline content in inoculated plants indicates a higher plant tolerance toward water stress (Gusain, Singh, & Sharma, 2015). PGPR produce various volatile compounds that provide protection against soil-borne pathogens. Application of Bacillus and Pseudomonas sp. protect Vitis vinifera and Mentha piperita against soil-borne pathogens (Cappellari, Chiappero, Santoro, Giordano, & Banchio, 2017). The volatile organic compounds of microbes play an essential role in plant growth, impart resistance against both biotic and abiotic stresses, and act as a potential biocontrol agent (Chandra et al., 2017). PGPR also provide relevant benefits to agroforestry management. Various PGPR such as Pseudomonas, Bacillus, Azotobacter, Variovorax, Paenibacillus, and Azospirillum have been used for various crops (rice, wheat, maize). Pseudomonas and Bacillus sp. have proven to be excellent biofertilizers (Turatto, Dourado, Zilli, & Botelho, 2017). PGPR enhance the germination of seeds, stimulate the rooting of cuttings, act as a biocontrol agent against various diseases, and increase the survival percentage after transplantation due to better root development. Some of the beneficial functions of PGPR are summarized in Table 1.1.

Table 1.1

1.4.1.2 Mycorrhizal fungi

Mycorrhizal fungi describe the symbiotic relationship between plant roots and fungi. Mycorrhizae colonize plant roots extracellularly and intracellularly. Ectomycorrhizal fungi form a net in the outer cell wall layers of plant roots without invading plant cells (species of Ascomycotina and Basidiomycotina). Arbuscular mycorrhizal fungi (AMF) are the most important endophytic fungi that colonize plants intracellularly and make the arbuscules and vesicles in plant roots. The association between plant roots and fungi is mutual in that plants provide carbohydrate to mycorrhizal fungi and, in turn, get nutrients and water from the soil with their help. AMF form a symbiotic association with approximately 93% of the terrestrial plant family. AMF belong to glomeromycotina having orders Glomerals, Archaeosporales, Diversisporales, and Paraglomerales (Spatafora et al., 2016). AMF form the massive network of hyphae in the soil, thus increasing nutrient and water absorption by plants. Plants provide carbohydrate and lipid to AMF; in turn AMF enhance the uptake of nutrients and promote the uptake of phosphorus, iron, zinc, and nitrogen, thus enhancing crop growth and productivity by reducing the application of chemical fertilizers. Due to intensive practices of conventional agriculture, the diversity of mycorrhizal fungi have decreased, leading to the reduction in the ecosystem functionality of mycorrhizal fungi (Gianinazzi et al., 2010; Oehl et al., 2004). AMF can be used as a biofertilizer for sustainable agriculture as an alternative to chemical fertilizers and increasing the nutritional quality of crop products with higher productivity.

Inorganic phosphate transporter (Pi) was reported in the Glomus versiforme that increased the absorption of phosphate from the soil (Parihar et al., 2020). The mycorrhizal association also has a role in the detoxification of both inorganic and organic pollutants in the soil. The application of mycorrhizal fungi inoculum in highly degraded soil leads to overcoming the situation of biotic and abiotic stress in the soil, helping to restore soil health (Verbruggen, Van Der Heijden, Rillig, & Kiers, 2013). Application of consortia of mycorrhizal fungi is more effective in the agricultural system than the application of single mycorrhizal sp. (Crossay et al., 2019). Some of the beneficial functions of AFM are summarized in Table 1.2.

Table 1.2

1.4.1.3 Actinomycetes

Actinomycetes are a vast group of prokaryotes comprising six classes and six orders having both cultivable and noncultivable sp. Actinobacteria are gram-positive bacteria that may be aerobic or anaerobic and exhibit variation morphologically, physiologically, and biochemically. They also have various pigmentation known as melanoid polymers, which exhibit similarity with humic acid present in the soil (Barka et al., 2016). Production of geosmin, an organic compound, by actinomycetes is accountable for the characteristic earthy odor. Actinomycetes adhere to the epidermal layer of plant roots and subcortical root cells, and they colonize plant roots endophytically. Arthrobacter, Corynebacterium, Micrococcus, Rhodococcus, Nocardia, Streptomyces, Microbacterium, Microbispora, Micromonospora, Streptosporangium, Streptoverticillium, and Frankia are some important genera belonging to actinomycetes. Actinomycetes have the ability to produce diverse bioactive compounds essential for human health and agriculture. More than 10,000 secondary metabolites known to be produced by these microbes have antimicrobial, antitumor, and antiinflammatory properties (Manivasagan, Venkatesan, Sivakumar, & Kim, 2014). Actinomycetes produce phytohormone and different organic acids that enhance plant growth under various abiotic and biotic stress (Bhatti, Haq, & Bhat, 2017). Actinomycetes play a key role in nitrogen fixation, phosphate solubilization, and siderophore production, thus increasing the availability of these nutrients for plants (Bouizgarne & Aouamar, 2014). Actinomycetes also produces various volatile organic compounds having a role in the suppression of various plant pathogens, acting as a chemical signal for communication, biofilm formation, mycelium formation, and modulating the pH of the soil (Lewin et al., 2016). Actinomycetes are a reservoir of various lytic enzymes (protease, amylase, pectinase, lipase, xylanase, exo- and endoglucanase). These lytic enzymes are responsible for plant cell wall degradation and help microbes to gain entry inside the plants (Bhatti et al., 2017). Lytic enzymes, chitinases, peroxidases, dextranases, cutinases, and laccases produced by actinomycetes degrade the cell wall of fungal pathogens inhibiting their growth (Martínez-Hidalgo, Galindo-Villardón, Trujillo, Igual, & Martínez-Molina, 2014). Actinomycetes remain in the soil with high cell density and viability thus enhancing plant growth and health by various means. These microbes can be used as a biopesticide, insecticide, biocontrol agent, and biofertilizer. Some of the beneficial functions of actinomycetes in agriculture are summarized in Table 1.3.

Table 1.3

1.4.2 Nutrient management by beneficial microbes

According to Miao, Stewart, and Zhang (2011) nutrient management is a science of optimum use of soil, hydraulic factors, and critical NPK (nitrogen, phosphorus, potassium) inputs. It also optimizes nutrient use efficiency and improves soil health, plant growth, and environment (Miao et al., 2011). Plants take in various nutrients from the rhizosphere in the soil and from the phyllosphere in the atmosphere (Turner et al., 2013). A special environment is created in the rhizosphere with the help of diverse compounds released by the plant root system.

Nowadays, people are more concerned about the quality of food. Due to the ever-growing population and climate change the pressure of producing food with good quality has become challenging. The pressure is increased due to the reduction of farmlands, rising labor costs, etc. Synthetic fertilizers are being used in agricultural fields to fulfill the requirement of macro and micronutrients, leading to environmental pollution. Nutrient mobilization through microbes is a chief driver of plant growth and occasionally turns into a rate-limiting step in ecosystem productivity (Schimel & Bennett, 2004). For sustainable agriculture, beneficial microbes in the soil are being used, which play a vital role in nutrient management (Adhya et al., 2015). Among the beneficial microbes, bacteria and fungi play a key role in the breakdown of soil organic matter and the recycling of nutrients (Neill & Gignoux, 2006).

1.4.2.1 Role of beneficial microbes in phosphorus solubilization

Plants obtain phosphorus as phosphate ions from the soil. Phosphorus solubilizing microorganisms (PSMs) play a crucial role in phosphorus nutrition. PSMs enhance the phosphorus availability in plants through solubilization and mineralization (Chandra, Srivastava, & Sharma, 2016; Sharma, Sayyed, Trivedi, & Gobi, 2013). Beneficial microbes produce organic acids and acid phosphatase that reduces soil pH during phosphorus solubilization. In comparison to fungi, bacteria are more efficient in phosphorus solubilization (Sharma et al., 2013). When phosphorus solubilizing bacteria (PSB) are coinoculated with mycorrhizal fungi or some other beneficial bacteria, their efficiency of phosphorus solubilization increases (Mohammadi, 2012). Rhizospheric strains of Pseudomonas, Bacillus, Rhizobium, Enterobacter, and many endophytic bacteria are reported as efficient phosphate solubilizers (Khan, Zaidi, & Wani, 2007). Among fungal genera, Aspergillus and Penicillium are efficient phosphorus solubilizers (Saxena, Basu, Jaligam, & Chandra, 2013).

1.4.2.2 Role of beneficial microbes in potassium solubilization and mobilization

Potassium is a vital component of plant nutrition and performs various biological and physiological functions. Potassium is usually abundant in soil. According to Bertsch and Thomas (1985), the total potassium content present in the topsoil ranges from 3000 to 1,00,000 kg/ha. Potassium is present in four forms: (1) water soluble, (2) exchangeable, (3) nonexchangeable, and (4) structural or mineral (Sparks & Huang, 1985). Changes in soil pH, texture, temperature, moisture level, and oxygen level determine the extent of release of potassium from soil (Basak & Biswas, 2009). Several beneficial microbes have the capability of potassium mobilization. Microbes produce organic acids that mobilize potassium present in feldspar, muriate of potash, or waste mica, making it available for plants (Sessitsch et al., 2013). Beneficial bacterial sp. such as Arthrobacter, Azotobacter sp., Acidithiobacillus ferrooxidans, Bacillus mucilaginosus, Bacillus edaphicus, Klebsiella sp., Pseudomonas sp., Paenibacillus sp., and Rhizobium sp. are reported to mobilize insoluble potassium into soluble form in the soil for better plant nutrition (Liu, Lian, & Dong, 2012).

1.4.3 Role of beneficial microbes in production of plant growth regulators

Microbes produce various plant growth regulators, which combine with plant-produced phytohormones and exert various physiological functions in plants. Microorganisms residing in plant rhizospheres synthesize and release auxins (Kapoor, Kumar, Patil, & Kaur, 2012). Soil microorganisms are responsible for producing various bioactive compounds, which affect plant growth and development (Ahemad & Kibret, 2014). PGPR produce various phytohormones such as IAA, gibberellic acid, and cytokinin, which enhances plant growth (Kloepper, Gutierrez-Estrada, & Mclnroy, 2007). Most of the PGPR, either symbiotic or free-living species, produce IAA and gibberellic acid in the rhizosphere, which have enormous potential in the enhancement of root surface area and a number of root tips of plants (Han et al., 2005). According to many studies, fungi also play a vital role in plant growth promotion (Murali, Amruthesh, Sudisha, Niranjana, & Shetty, 2012). Beneficial fungal species produces various antibiotic and lytic enzymes such as chitinases, proteases, and glucanases, which act as biocontrol agents. Various Trichoderma strains are also reported to colonize plant roots and enhance plant growth and development (Saba et al., 2012).

1.4.4 Beneficial microorganisms as biofertilizers and biopesticides

The use of beneficial microbes as biofertilizers and biopesticides represent a sustainable approach in the modern agriculture system (Bhardwaj, Ansari, Sahoo, & Tuteja, 2014). Microbial biofertilizers comprises living microorganisms. These biofertilizers, when applied to the soil, seed, or plant surface, enhance plant growth by increasing the uptake of nutrients through plant roots (Bhattacharyya & Jha, 2012). Microbial biopesticides comprise living microorganisms that produce various compounds such as antibiotics, HCN, hydrolytic enzymes, and siderophore, promoting plant growth by inhibiting or killing phytopathogens (Chandler, Davidson, Grant, Greaves, & Tatchell, 2018). Various beneficial microbes such as Pseudomonas, Bacillus, Rhizobium, Azotobacter, Enterobacter, Variovorax, Azospirillum, Allorhizobium, Acetobacter, Azorhizobium, Aspergillus, Bradyrhizobium, Mesorhizobium, and penicillium have the vital capacity to be an efficient biofertilizer or biopesticide (Vessey, 2003).

1.4.5 Role of beneficial microbes in abiotic stress

Abiotic stress, such as drought, extreme temperature, flood, excess light, salinity, and heavy metal toxicity, is a chief factor that negatively affects plant growth and development. According to Wang, Vinocur, and Altman (2003), abiotic stress can reduce the productivity and yield of major crops by more than 50% of arable land throughout the world by the year 2050. Ever growing world population creates new challenges for agriculture. To feed this huge population, there is a need to increase food productivity at the same pace to ensure food security. Abiotic stress alters nutrient acquisition and biosynthetic activities, inhibiting plant growth. Cell differentiation and growth require nutrients, energy, and biosynthetic activities. Restriction in any one of the factors leads to growth retardation and ultimately death of plants. Among the abiotic factors, drought is a major abiotic stress that reduces plant growth and, as such, plant yield. Drought is a threat to agricultural productivity worldwide (Gornall et al., 2010). Due to their sessile nature, plants modulate themselves morphologically, physiologically, and biochemically under stress conditions. Plants show various physiological changes such as the closure of stomata, expression of aquaporins, and vacuolar H-pyrophosphatases, maintenance of cell turgidity, and accumulation of osmolytes for osmotic adjustments (Sati, Veni, Pandey, & Samant, 2021). Under drought stress, ethylene concentration also increases, impairing plant growth (Burg, 1973). Reactive oxygen species (ROS) accumulate and lead to osmotic stress deteriorating the integrity and functionality of cells and ultimately plant survival (Gill & Tuteja, 2010). The rhizosphere and the endosphere are the main hotspots for beneficial microbes (Berg, Grube, Schloter, & Smalla, 2014). Among the beneficial microbes, mycorrhizal fungi and PGPB have the capability of modulating plants’ physiological responses under stress conditions, thereby increasing plant tolerance toward abiotic stress conditions. According to Perez-Montano et al. (2014), plants inoculated with beneficial microbes increased their growth by 40% under stress conditions suggesting the potential of beneficial microbes in agriculture under various stress