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Potassium (K) is the foremost macronutrients for growth of plant, soil health and fertility. The huge application of NPK chemical fertilizers negatively impacts the economy and is a threat to environmental sustainability. The rapid depletion of K mineral in soil is due to the application of agrochemicals agricultural fields for the production of crops in India. In present investigation, K-solubilizing microbes (KSM) were isolated and enumerated from cereal crops growing in Sirmour Himachal Pradesh. A total 125 bacteria were isolated and screened for K- solubilization on Aleksandrov agar plates and found that 31 bacterial strains exhibited K-solubilization. These 31 K-solubilizing strains of bacteria were additionally screened for other plant growth promoting (PGP) potential including solubilization of minerals, production of siderophores, ammonia, hydrogen cyanide and indole acetic acids. The performance of an efficient K-solubilizer was evaluated for plant growth promoting ability in pot assay under in vitro conditions. The strain EU-LWNA-25 positively influenced shoot length, fresh weight, carotenoids and total sugar content than the full dose, half dose and control. The strain enhancing physiological and growth parameters was identified by BLASTn analysis as Pseudomonas gessardii EU-LWNA-25. K-solubilizing plant growth promoting bacteria could be suitable bioinoculants for Rabi seasonal crops and overcomes the challenges of sustainable agriculture in K-deficient soil.

Soil is the basic requirement for agriculture crop production and simultaneously the microbial activity is important to improve soil health for healthy crop growth because microbial communities play an important role in building a complex link between plants and soil. Microbiomes from plants, soil and extreme environments are naturally gifted with amazing capabilities which play significant roles in the maintenance of global nutrient balance and ecosystem functions. The microbiomes from diverse niches have in fact emerged as potential tools for improving the plant growth and productivity by diverse mechanisms include solubilization of nutrients, nitrogen fixation, hormonal stimulation as well as biotic and abiotic stress tolerance. Further, these microbiomes have an immense potential to maintain soil health and fertility. Thus, dependent on their mode of action and effects, these microbiomes can be used as biofertilizers, biopesticides, plant strengtheners, and phytostimulators which will play a major role in improving productivity and achieving sustainability in an eco-friendly, economical and cost effective manner.

The Himalayas are one of the most mystical, yet least studied terrains of the world. One of Earth's greatest multifaceted and diverse montane ecosystems is also one of the thirty-four global biodiversity hotspots of the world. These are supposed to have been uplifted about 60-70 million years ago and support, distinct environments, physiography, a variety of orogeny, and great biological diversity (plants, animals, and microbes). Microbes are the pioneer colonizer of the Himalayas that are involved in various bio-geological cycles and play various significant roles. The applications of Himalayan microbiomes inhabiting in lesser to greater Himalayas have been recognized. The researchers explored the applications of indigenous microbiomes in both agricultural and environmental sectors. In agriculture, microbiomes from Himalayan regions have been suggested as better biofertilizers and biopesticides for the crops growing at low temperature and mountainous areas as they help in the alleviation of cold stress and other biotic stresses. Along with alleviation of low temperature, Himalayan microbes also have the capability to enhance plant growth by availing the soluble form of nutrients like nitrogen, phosphorus, potassium, zinc, and iron. These microbes have been recognized for producing plant growth regulators (abscisic acid, auxin, cytokinin, ethylene, and gibberellins). These microbes have been reported for bioremediating the diverse pollutants (pesticides, heavy metals, and xenobiotics) for environmental sustainability. In the current perspectives, present review provides a detailed discussion on the ecology, biodiversity, and adaptive features of the native Himalayan microbiomes in view to achieve agro-environmental sustainability.

Soil microbial diversity is very important part of ecosystem as it plays a significant role in biogeochemical cycles. Currently, health of environment has been depleted due to growing population of the world and human activities like industrialization, overexploitation of chemical based products in agriculture and urbanization. These problems are now being of major concern of the environmentalist and to fix these problems has become an emergence. Soil microbiomes have been recognized as a potent tool for the sustainable agriculture and environment. Such microbes exhibit hidden talent to overcome the environmental related problem like pollution and soil degradation. In agriculture, soil microbiomes can be used as a biofertilizers over the chemical based products. Soil microbes help in reclamation of soil fertility, alleviation of diverse abiotic stresses, and nutrients stress that help in plant growth and development. Soil microbes help plant for growth via direct mechanisms for enhancing plant growth directly in a sustainable way like solubilization of nutrients (P, K, and Zn), fixation of nitrogen and chelation of iron as well as via indirectly by controlling pathogen growth and alleviating abiotic stress. In environment, beneficial soil microbiomes help in the degradation of environment pollutants like chemical pesticides and industrial waste by enzymatic actions and biosorption techniques. Present review deals with the diversity of soil microbiomes and their role in plant growth promotion and remediation of diverse environmental pollutants for agro-environmental sustainability.

As one of the most important and essential macronutrients next to nitrogen, phosphorus (P) is important for plant development, but it is the least mobile nutrient element in plant and soil. Globally, P is mined from geological sediments and added to agricultural soils so as to meet the critical requirements of crop plants for agronomic productivity. Phosphorus exists in soil in both organic and inorganic forms. The various inorganic forms of the element in soil are salts with calcium, iron, and aluminum, whereas the organic forms come from decaying vegetation and microbial residue. There is a huge diversity of plant microbiomes (epiphytic, endophytic, and rhizospheric) and soil microbiomes that have the capability to solubilize the insoluble P and make it available to plant. The main mechanism for the solubilization of inorganic P is by the production of organic acids, which lowers soil pH, or by the production of acid and alkaline phosphatases, which causes the mineralization of organic P. The P-solubilizing and -mobilizing microorganisms belong to all three domains, comprising archaea, bacteria, and eukarya. The strains belonging to the genera Arthrobacter, Bacillus, Burkholderia, Natrinema, Pseudomonas, Rhizobium, and Serratia have been reported as efficient and potential P solubilizers. The use of P solubilizers, alone or in combination with other plant growth-promoting microbes as an eco-friendly microbial consortium, could increase the P uptake of crops, increasing their yields for agricultural and environmental sustainability.

Agriculture faces challenges to fulfil the rising food demand due to shortage of arable land and various environmental stressors. Traditional farming technologies help in fulfilling food demand but they are harmful to humans and environmental sustainability. The food production along with agro-environmental sustainability could be achieved by encouraging farmers to use agro-environmental sustainable products such as biofertilizers and biopesticides consisting of live microbes or plant extract instead of chemical-based inputs. The eco-friendly formulations play a significant role in plant growth promotion, crop yield and repairing degraded soil texture and fertility sustainably. Mineral solubilizing microbes that provide vital nutrients like phosphorus, potassium, zinc and selenium are essential for plant growth and development and could be developed as biofertilizers. These microbes could be plant associated (rhizospheric, endophytic and phyllospheric) or inhabit the bulk soil and diverse extreme habitats. Mineral solubilizing microbes from soil, extreme environments, surface and internal parts of the plant belong to diverse phyla such as Ascomycota, Actinobacteria, Basidiomycota, Bacteroidetes, Chlorobi, Cyanobacteria, Chlorophyta, Euryarchaeota, Firmicutes, Gemmatimonadetes, Mucoromycota, Proteobacteria and Tenericutes. Mineral solubilizing microbes (MSMs) directly or indirectly stimulate plant growth and development either by releasing plant growth regulators; solubilizing phosphorus, potassium, zinc, selenium and silicon; biological nitrogen fixation and production of siderophores, ammonia, hydrogen cyanide, hydrolytic enzymes and bioactive compound/secondary metabolites. Biofertilizer developed using mineral solubilizing microbes is an eco-friendly solution to the sustainable food production system in many countries worldwide. The present review deals with the biodiversity of mineral solubilizing microbes, and potential roles in crop improvement and soil well-being for agricultural sustainability.

Microbes are ubiquitous in nature, and plant-microbe interactions are a key strategy for colonizing diverse habitats. Fungi are producing a wide range of secondary metabolites and bioactive compounds, which are probable alternative sources of drugs and/or antibiotics. Fungi are associated with the crops and plays an important role in plant growth promotion and enhanced soil fertility using different PGP mechanism such as solubilization of phosphorus, zinc, potassium; production of plant growth regulator (auxins, cytokinin, gibberellins, ethylene and abscisic acid); hydrolytic enzymes (xylanases, laccase, pectinases, cellulases); and siderophores. Besides eliciting plant defence reaction against pathogens; PGP fungi also help in plant growth promotion and alleviation of different abiotic stresses under harsh environments. The PGP fungi have reported from different genera of phyla Chytridiomycota, Zygomycota, Glomeromycota, Ascomycota, and Basidiomycota. Fungi also have significant potential applications in various industries like medical, and food. In the medical applications, fungi and fungal products are used to control disease in human and animals. In the fermentation industries fungi used to make alcoholic beverages, cheeses, bread, kefir, yogurt and various other food preparations and the agricultural sectors used to make plant healthy and protects to pathogens. The present review, deals with the biodiversity of beneficial fungi from different habitats and their biotechnological applications in plant growth promotion and soil health.

Drought is the most limiting factors affecting plant development. It severely affects the crops and leads to serious reductions in yield. There are certain nutrients which also act as limiting factor for plants such as phosphorus and nitrogen. Under the conditions of nutrient limitations, growth is greatly reduced. Plant associated microbiome are gaining attention as they help the host (plant) to combat stress conditions. In the present study, stress-adaptive and phosphorus-solubilizing microbes were isolated from rhizosphere of different crops such as wheat, maize, foxtail millet, and finger millet growing in NW Indian Himalayas. A total of 70 microbes were isolated using different defined and selective growth media. The isolated microbes were screened for plant growth promoting (PGP) ability of phosphate solubilization using three different insoluble phosphorus (P) substrates (apatite, tricalcium phosphate and rock phosphate) under the drought stress conditions (5–8% PEG-8000). Among isolated microbes 27 isolates exhibited P-solubilizing attribute under the water deficient conditions. The two efficient drought-adaptive and P-solubilizing isolates were identified as Acinetobacter calcoaceticus EU- LRNA-72 and Penicillium sp. EU-FTF-6, respectively, by 16S rRNA and 18S rRNA gene sequencing. The isolates EU- LRNA-72 and EU-FTF-6 were evaluated for plant growth promoting (PGP) traits and mitigation of drought stress in foxtail millet under the controlled and natural conditions. The isolates A. calcoaceticus EU- LRNA-72 and Penicillium sp. EU-FTF-6 efficiently mitigated the adverse effects of drought in foxtail millet by enhancing the accumulation of glycine betaine, proline, sugars, and decreasing lipid peroxidation. The drought tolerant P-solubilizing microbes could be useful for plant growth promotion and mitigation of drought stress for crops growing under the water deficient conditions.

Endophytic microbes residing inside the tissues of plants play a significant role to enhance the growth and health of plants by different plant growth-promoting mechanisms. In the present investigation, N2-fixing endophytic bacteria were isolated and characterized by plant growth. A total of one hundred fifty-nine endophytic bacteria were isolated from surface-sterilized roots and stem of different genotypes of wheat growing in the Divine Valley of Baru Sahib, Himachal Pradesh. The isolated bacterial endophytes were screened in vitro for plant growth-promoting attributes. Out of one hundred fifty-nine, thirteen endophytic bacteria were selected based on multifarious plant growth-promoting attributes. Among plant growth-promoting activities, hydrogen cyanide producers (19%) were higher when compared to siderophores producers (16%) and P-solubilizers (16%), ammonia producers (14%), K-solubilizers (14%), IAA producers (12%), Zn-solubilizers (5%), N2-fixers (2%) and biocontrol (2%). One of the isolates EU-B2RT.R1 demonstrated that a significant level of nitrogenase activity, P-solubilization and IAA production was identified as Acinetobacter guillouiae EU-B2RT.R1 based on 16S rRNA gene sequencing and BLAST analysis. Acinetobacter guillouiae EU-B2RT.R1, exhibiting multifarious beneficial traits, is further evaluated for plant growth promotion of wheat cultivar PBW 343+Lr24+GPC in pot experiment under greenhouse conditions. The Acinetobacter guillouiae EU-B2RT.R1 with multifarious plant growth-promoting activity has emerged as one of the efficient biofertilizers that need to be explored for sustainable agriculture.

Drought stress is among the most destructive stresses for agricultural productivity. It interferes with normal metabolic activities of the plants resulting, a negative impact on physiology and morphology of the plants. The management of drought stress requires various adaptive and alleviation strategies in which stress adaptive microbiomes are exquisite bioresources for plant growth and alleviation of drought stress. Diverse drought adaptive microbes belonging to genera

Climate change is emerging as a crucial issue with global attention and leading to abiotic stress conditions. There are different abiotic stress which affects the crop production among which drought is known to be most destructive stress affecting crop productivity and world's food security. Different approaches are under consideration to increase adaptability of the plants under drought stress with plant-microbe interactions being a greater area of focus. Stress-adaptive microbes either from the rhizosphere, internal tissue, or aerial parts of plants have been reported which through different mechanisms help the plants to cope up with drought and also promote their growth. These mechanisms include the accumulation of osmolytes, decrease in the inhibitory levels of ethylene by aminocyclopropane-1-carboxylate (ACC) deaminase enzyme, and furnishing the unavailable nutrients to plants. Microbial genera including Azotobacter, Bacillus, Ochrobactrum, Pseudomonas, and Serratia are known to be self-adaptive and growth promoters under drought stressed conditions. Stress-adaptive plant growth promoting (PGP) microbes thus are excellent candidates for stress alleviation in drought environment to provide maximum benefits to the plants. The present review deals with the effect of the drought stress on plants, biodiversity of the drought-adaptive microbes, mechanisms of the drought stress alleviation through enhancement of stress alleviators, reduction of the stress aggravators, and modification of the molecular pathways as well as the multiple PGP attributes of the drought-adaptive microbes.

Endophytic fungal communities have attracted a great attention to chemists, ecologists, and microbiologists as a treasure trove of biological resource. Endophytic fungi play incredible roles in the ecosystem including abiotic and biotic stress tolerance, eco-adaptation, enhancing growth and development, and maintaining the health of their host. In recent times, endophytic fungi have drawn a special focus owing to their indispensable diversity, unique distribution, and unparalleled metabolic pathways. The endophytic fungal communities belong to three phyla, namely Mucoromycota, Basidiomycota, and Ascomycota with seven predominant classes Agaricomycetes, Dothideomycetes, Eurotiomycetes, Mortierellomycotina, Mucoromycotina, Saccharomycetes, and Sordariomycetes. In a review of a huge number of research finding, it was found that endophytic fungal communities of genera Aspergillus, Chaetomium, Fusarium, Gaeumannomyces, Metarhizium, Microsphaeropsis, Paecilomyces, Penicillium, Piriformospora, Talaromyces, Trichoderma, Verticillium, and Xylaria have been sorted out and well characterized for diverse biotechnological applications for future development. Furthermore, these communities are remarkable source of novel bioactive compounds with amazing biological activity for use in agriculture, food, and pharmaceutical industry. Endophytes are endowed with a broad range of structurally unique bioactive natural products, including alkaloids, benzopyranones, chinones, flavonoids, phenolic acids, and quinines. Subsequently, there is still an excellent opportunity to explore novel compounds from endophytic fungi among numerous plants inhabiting different niches. Furthermore, high-throughput sequencing could be a tool to study interaction between plants and endophytic fungi which may provide further opportunities to reveal unknown functions of endophytic fungal communities. The present review deals with the biodiversity of endophytic fungal communities and their biotechnological implications for agro-environmental sustainability.

Drought is a very common abiotic stress worldwide in arid and semiarid areas. It decreases the growth and yield of the crops. Due to drought stress, there is insufficient intake of the nutrients, the low rate of photosynthesis and limited supply of water in plants. Inoculating crops with plant growth-promoting rhizobacteria (PGPR) mitigates the deleterious effects of stress by promoting beneficial effects such as helping them in the acquisition of less available nutrients, increasing the levels of plant growth regulators, improving the physiological health of the plants. In the present study, drought-tolerant phosphorus-solubilizing rhizobacteria with multifunctional plant growth-promoting attributes were isolated from different cereal crops grown in the Divine Valley of Baru Sahib, Himachal Pradesh, using a different nutrient combination. A total of 86 bacteria were isolated from different growth media. All 86 could tolerate 5% PEG, and 19, 6 and 6 isolates could tolerate 6%, 7% and 8% PEG-8000, respectively. Among 86, 48 drought-adapted and P-solubilizing strains were selected and screened for diverse PGP attributes such as solubilization of potassium and zinc, production of siderophores, hydrogen cyanide, ammonia and 1-aminocyclopropane-1-carboxylate deaminase. The efficient drought-adaptive P-solubilizing strain was used for seed germination and plant growth-promoting ability in different pot assays under laboratory and greenhouse conditions at different water regimes. The strain EU-LWNA-33 positively influencing the growth parameters and physiological parameters was identified using 16 S rRNA gene sequencing as Pseudomonas libanensis. To our knowledge, this is the first report for P. libanensis EU-LWNA-33 to solubilize a considerable amount of P under the water-deficient conditions. The use of stress-adaptive and P-solubilizing PGPR provides significant promise to overcome the challenges of sustainable agriculture in stressed environmental conditions.