PREFACE India has been predominantly a country of agriculture and more than 70% of people depend on agriculture and agricultural produce. Exponential rise in population coupled with industrialization and urbanization has demanded increase in agricultural produce with depleting land coverage. Under the Green revolution-I, enhanced application of agrochemicals significantly increased crop productivity. However, excessive use of chemical fertilizers not only adversely affects the soil health & the quality of produce but also contaminate the soil. It is also not cost effective. But over the past couples of decades, both developed and developing countries are harvesting the impact of Green Revolution I. The residuals of agrochemicals applied in the crop fields drastically affected the soil health; in terms of nutrient availability, soil microbial diversity and increased pathogen attack on the crops. In India states like Punjab and Haryana, which are otherwise called as the kitchen house of the country, fail to develop crop without fertilizer application. In Green Revolution-II, emphasis is being given on organic farming. In this perspective, soil microorganisms with advantageous effect on soil & plant health vis-a-vis growth & yield, correspond to be an effective alternative to conventional agricultural practices. Biofertilizers are live formulation of microbial inoculants that enhances soil fertility and crop productivity, thus, can be an ideal supplement / substitute to chemical fertilizers. The commercial exploration of such biological organisms is of recent interest. In the era of sustainable agriculture, organic farming has globally emerged as a priority area in view of the growing demand for safe & healthy food and long term sustainability. It not only ensures food safety, but also adds to the biodiversity of soil. The additional advantages of biofertilizers include longer shelf life causing no adverse effects to ecosystem. Organic farming includes application of compost, biofertilizers, biopesticides etc. which may not serve as a complete substitute but can be effective supplement to decrease application of agrochemicals. Organic farming is mostly dependent on the natural microflora of the soil which constitutes all kinds of useful bacteria, cyanobacteria, fungi including the arbuscular mycorrhiza fungi (AMF) and plant growth promoting rhizobacteria (PGPR). These bacteria also plays an important role in agricultural crops and termed as Agriculturally Important Microorganisms (AIMs). AIMs have diverse applications in agriculture, horticulture, and forestry. These microbes also play a key role in crop protection through enhancing the disease resistance capacity of plants against pathogens, exhibiting antagonistic activities or acting as biotic elicitors. The book, Agriculturally Important Microorganisms: Mechanisms and Applications enlighten the inherent potential of AIMs in inter and intra community interactions, metabolite production and plant protection with latest information available in the relevant field. The field is so large and the interest in PGPR microbiota is so varied that the topics covered will make the book more informative & meaningful to be accepted by scientists, academia and researchers. This book can be largely informative on the biofertilizers in sustainable agriculture by enhancing soil fertility, plant tolerance and crop productivity, plant-microbe interactions and their inherent principles for plant protection, mitigation of salt stress, biological N2 fixation, plant growth promotion, Potassium Solubilizing Microorganisms for advances in nutrition for rice and other crops. In addition, nanofertilizers for sustainable agriculture will provide new frontiers for future research. It will also provide key knowledge to cutting edge biotechnological methods applied in soil and agricultural microbiology.

Abstract Microbes are ubiquitously found in the environment. Their interaction with other living organisms could either be pathogenic or beneficial in nature. Soil as a rich source of microbes, researchers have extensively studied the plant-microbe interactions. The soil microbes supply the nutrients deficit plants with essential growth elements such as nitrogen, phosphorous, potassium, etc. and improve the texture and quality of the soil. Due to the destructive nature of chemical fertilizers to soil and environment, it was required to generate a more ecofriendly means of increasing the soil fertility. This led to the development of microbes based biofertilizers. The primary benefit of biofertilizers is to promote a healthy soil environment along with supplying essential nutrients to the plant. Again, biofertilizers can be tailor-made according to the specific plant or the climatic conditions. Fungal and bacteria based biofertilizers, either alone or in combinations are formulated for the plants. Lately, liquid fertilizers are increasingly finding their use in the biofertilizer industry due to their ease in manufacture and prolonged effect on plant growth. The scope of this chapter lays on the currently popular biofertilizers and recent trends in the biofertilizer industry.

Abstract The concern of global food security is growing day by day as the agriculturally available land is reducing each day with the expansion of industrialization and urbanization. During the course of urban and industrial development, crop production is greatly affected by global warming, contamination of hazardous materials, salinity and drought. To combat against such adversities, scientists have taken several additives measurement like development of transgenic crops, application of indigenous plant growth promoting microbes etc. for sustainable agriculture. Use of plant growth promoting microbes is getting popular day-by-day as they occupy a privilege niche with the autochthonous flora of specific environment. For the expanse of food and shelter, the microbes supply a wide range of plant regulators (e.g. auxins, cytokinins, gibberellins, ABA, phenols, NH3 etc.), antibiotics, alkaloids, steroids, terpenoids, diterpenes, enzymes (e.g. cellulases, lipases, proteinase, esterases etc.) etc. for overall development of the plant. Apart from growth promotion, it also protects the plants against pathogenic invasion creating a competition with pathogens for nutrition and habitat. In near future, formulation of different plant growth promoting bacteria (like alpha- Azorhizobium, Azospirillum, Ancylobacter, Rhizobium, Bradyrhizobium, Sinorhizobium, Novosphingobium sp., beta- Burkholderia sp., gamma- Acinetobacter, Aeromonas, Azotobacter, Enterobacter, Klebsiella, Pantoea, Pseudomonas, Stenotrophomonas sp. Proteobacteria, Bacillus sp., Paenibacillus sp. and Actinobacteria- Microbacterium sp. etc.) and fungus (Aspergillus, Trichoderma, Penicillium etc.) may reduce the use of pesticides and chemical fertilizer to promote greener ways of crop production.

Abstract Agriculture is one of the most important factors contributing to the economic growth of India. Out of the 329 million hectares of India’s geographical area, about 114 million hectares are under cultivation. There are 17 essential elements required for proper plant growth. Of the mineral elements, the primary macronutrients (nitrogen, phosphorous, and potassium) are needed in the greatest quantities and are most likely to be in short supply in agricultural soils. Secondary macronutrients are needed in smaller quantities, and are typically found in sufficient quantities in agricultural soil, and therefore do not often limit crop growth. Micronutrients, or trace nutrients, are needed in very small amounts and can be toxic to plants in excess. Silicon (Si) and sodium (Na) are sometimes considered essential plant nutrients, due to their ubiquitous presence in soils. The economy of India thrives on agriculture, the most practiced occupation in the country. Agricultural fertilizers are essential to enhance proper growth of plants and crop yield. Recently, farmers have been using chemical fertilizers for quicker and better yield. But these fertilizers endanger ecosystems, soil, plants, human and animal lives. In contrast, naturally grown biofertilizers not only give a better yield, but are also harmless to humans. This chapter aims to study the biofertilizers play a key role for enhancing economic development of sustainable agriculture (EDSA) in comparison to chemical fertilizers. Biofertilizers improve the crop yields, plant resistance, soil health, profit to farmers, and the benefit to cost ratio of biofertilizers were higher than chemical fertilizer, proved that the biofertilizers would lead to better sustainable economic development for the farmers and their country.

Abstract Soil salinity is one of the major environmental stresses affecting crop productivity and soil health drastically, particularly in arid and semi-arid areas. Most of the vegetable crops being salt sensitive, grow poorly in saline and alkaline soils. Soil salinity affects crops mainly due to the osmotic stress and excessive accumulation of toxic ions (Na+, Cl-, and SO4 2-), whereas alkali soils are generally characterized by poor physical conditions due to high concentrations of bicarbonate (HCO3 -) and carbonate (CO3 2-) as well as high exchangeable Na+. Excessive concentrations of sodium chloride (NaCl) in soil or irrigation water can induce several morphological, physiological, and biochemical responses in plants leading to stunted growth and yield. This is due to osmotic (i.e., water deficit) and ionic (i.e., Na+ and Cl-) effects on nutrient uptake/translocation and metabolic processes such as nitrogen assimilation, photosynthesis, and protein synthesis. Plant growth promoting microbes (PGPMs) are considered as promising tools to overcome the limitations of salinity on crop growth and productivity. Many PGPMs can enhance tolerance of crops to salt stress by increasing nutrient uptake through better solubilization of nutrients like phosphorus and zinc, and also by production of small peptides, volatiles and metabolites with hormone activities such as indole-3-acetic acid or auxin analogs in the rhizosphere. This chapter discusses the benefits of PGPMs in plant adaptations to salt stress conditions.

Abstract In recent years, significant studies have been carried out on Plant growth promoting rizhobacteria (PGPR) to replace the usage of pesticides and fertilizers to improve the plant health. Plant growth promoting rizhobacteria (PGPR) is a group of rhizosphere bacteria, which are symbionts to plants and influence their growth by providing plant growth promoting substances. Different bacterial genera act as plant growth promoting rizhobacteria (PGPR): Pseudomonas sp., Rhizobium sp., Azotobacter sp., Bacillus sp. Pseudomonads are gram negative rods, aerobic, fluorescent, motile and are able to produce siderophores which influence plant growth. There are multiple potential traits offered to the plants by plant growth promoting (PGP) Pseudomonas sp. are (1) Biocontrol agent against plant pathogens (2) Induced systemic resistance, which is a defense mechanisms in plants preceding to pathogenic attack (3) Influence of plant growth promoting (PGP) Pseudomonas sp.on agricultural crops (4) Siderophores, which are low molecular, high affinity iron chelating compounds which benefits the plants to acquire iron molecules (5) Nitrogen fixation (6) Phytoremediation of heavy metals (7) Solubilization of inorganic phosphates (8) Secretion of plant hormones (9) Bacteriocins(10) Antifungal factors (11) Antibiosis traits and (12) Endophytic PGP Pseudomonas sp.

Abstract Sustainable agriculture is vital in today’s world as it offers the potential to meet our agricultural needs, something that conventional agriculture fails to do. Current soil management strategies are mainly dependent on inorganic chemical fertilizers, which caused a serious threat to human health and environment. To overcome the ecological problems resulting from the loss of plant nutrients and to increase crop yields in the absence of resources for obtaining costly fertilizers, microscopic organisms that allow more efficient nutrient use or increase nutrient availability can provide sustainable solutions for the present and future agricultural practices. Microbial populations are instrumental to fundamental processes that drive stability and productivity of agro-ecosystems. Several investigations addressed at improving understanding of the diversity, dynamics and importance of soil microbial communities and their beneficial and cooperative roles in agricultural productivity. Thus the technique, which uses microscopic organism as biofertilizer, is environment friendly and ensures safe and healthy agricultural products. In this chapter we aim to provide a brief overview of potential use of biofertilizer for attaining sustainability of agro-ecosystem.

Abstract Nitrogen (N2) is an essential nutrient for every organisms. It is the building block of many biological molecules. Atmosphere contains 79% of N2 gas which cannot be used by plants directly as it is chemically inert. Many diazotrophs like bacteria and cyanobacteria have the capability to convert atmospheric dinitrogen into a usable form by means of Biological nitrogen fixation (BNF). N2 fixation is generally three types i.e. Asymbiotic, Associative and Symbiotic. Asymbiotic N2-fixation also known as free living N2-fixation is under taken by some bacteria and cyanobacteria. In associative N2-fixation, some bacteria fix nitrogen in association with root of some grasses and cereal plants. In symbiotic nitrogen fixation, Rhizobium form root nodule in legumes and fix atmospheric N2 and convert it into the ammonia (NH3) by the help of Nitrogenase enzyme. This oxygen sensitive enzyme consist of two components i.e. di-nitrogenase (MoFe protein) and di-nitrogenase reductase (Fe protein) which are highly conserve in sequence and structure. The N2 fixing genes e.g. nod gene (nodulation gene) and the nif gene (nitrogen-fixing gene) are located in the plasmid which is also called mega plasmid. Symbiotic association between legume and rhizobium have agronomic importantance and reduce the use of N-fertilizers or even avoided. The long term use of the nitrogenous biofertilizer in the agricultural field is a promising approach to develop and fulfil N2 demand of the growing crop without causing any environmental hazard.

Abstract Potassium is a very essential nutrient element that is required for proper health, growth, functioning and productivity of plants. However, up to 98% of this very important mineral is held up in insoluble, unavailable forms in the soil and with only approximately 2% soluble form available for plant use. Biofertilizers add nutrients to the soil for plant use by some mechanisms like the breakdown of phosphorus, potassium, fixing nitrogen, and also synthesizing some substances which in turn enhance plant growth. These processes take place naturally. Microorganisms that solubilize potassium have demonstrated an increased potassium uptake by plants when added as bio-inoculants consequently resulting in increased yield by these plants. This article reviewed the methods of isolation of potassium solubilizing bacteria and fungi and their use as biofertilizers. Data are presented showing summary of researches conducted on potassium solubilizing microorganisms and their findings. Figures on production efforts of biofertilizers in India per year and by states are also added.

Abstract Potassium (K) is the third most essential macronutrient element for plants. More than 98% of K in agricultural soils are remained as insoluble organic and inorganic compounds or complexes that are unavailable for plant uptake. Nutrition of crop plants are heavily relied on application of expensive inorganic chemical fertilizers, which is a potential cause of environmental pollution. An eco-friendly alternative strategy for plant K nutrition could be the application of K solubilizing bacteria (KSB) as biofertilizer. Plant and soil-associated bacteria from diverse taxonomic genera such as Bacillus, Pseudomonas, Acidithiobacillus, Paenibacillus, Flectobacillus, Arthrobacter, Enterobacter, Sphingomonas, Paraburkholderia etc. have shown high K solubilizing activities and promote plant nutrition in K deficient soils. The mechanisms involved in their activities include acidolysis, chelation, exchange reactions, and enzymatic degradation of insoluble K minerals and other K complexes. However, inconsistency in the efficiency of KSB-based biofertilizer for crop production in diverse ecological settings is still a big challenge. Recent genomics, post-genomics and CRISPR-Cas genome editing approaches seem to be useful for a better understanding the underlying mechanisms of KSB and development of highly efficient K fertilizers for promoting sustainable agriculture. This chapter comprehensively reviews current updates of KSB-based biofertilizer and their potentials for promoting sustainable crop production. The role of genomics and post-genomics approaches for better understanding of the mechanisms of the functions of applied KSB-based biofertilizers in the crop field and mitigation of the existing inconsistency in the efficiency of KSB-based fertilizers are also discussed.

Abstract Agriculture provides food, feed, fiber and many other desired products for survival of human beings in the world. Modern agriculture emphasizes on use of hybrid seeds, high yielding varieties and chemical fertilizer to increase the crop productivity within a short period. Indiscriminate use of synthetic fertilizers has led to environmental pollution and deterioration of soil health, which results in depletion of essential plant nutrients and organic matter in soil. On account of the environmental hazard and soil infertility, biofertilizer concept was developed. Biofertilizer are natural fertilizers including bacteria, fungi and algae alone or in combination that augment availability of nutrients to the plants. However, due to its short shelf life period it may not be a suitable candidate for modern agriculture. Thus, it is the need of the hour to develop an economic and eco-friendly nano-biofertilizer for sustainable agriculture.

Abstract Phosphorus is the second important key element after nitrogen as a mineral nutrient in terms of quantitative plant requirement. Although abundant in soils, in both organic and inorganic forms, its availability is restricted as it occurs mostly in insoluble forms. The dynamics of phosphorus in soil is closely related to the dynamics of the biological cycle in which microorganisms play a central role. They also participate in the cycles of the most important macro and microelements such as phosphorus besides their major role in the decomposition of plant residues, creation of humus and maintenance of stable soil structure. Microorganisms affect the amount of phosphorus accessible to plants by means of mineralization of organic phosphorus compounds, immobilization of available phosphorus and solubilization of non-soluble phosphorus minerals such as tricalcium phosphate. Mineralization is catalyzed by microbiological enzymes phosphatases secreted by a diverse group of bacteria, fungi and other groups of microorganisms. Organic phosphorus mineralization in soil depends on several soil and environmental factors such as temperature, pH, soil moisture, degree of aeration. In this chapter the major emphasis is given on the transformation of P through microbiologically involving different enzymes and also the microorganisms involved in the process. Emphasis is also given on the factors that have profound influence on the microbial transformation of P in soil and ultimately making it available for plant uptake. This chapter also focuses on the mechanism of P solubilization, role of various phosphatases, impact of various factors on P solubilization and potential for application of this knowledge in managing a sustainable environmental system.

Abstract Rhizobia are soil bacteria that fix atmospheric dinitrogen after establishing symbiotic relationship inside the root nodules of legumes (Fabaceae). Plant Growth Promoting Rhizobacteria are the group of bacteria which thrive in the rhizosphere region and enhance the plant growth through direct & indirect mechanisms. Pulses are being inoculated with specific rhizobial strains to have better nodulation in India. The native rhizobial strains from the root nodules of legumes from different agroclimatic zones of Odisha was isolated, characterised and screened for PGP activities. Out of all eleven isolates showed similar characteristics with the family Rhizobiacae. Among them six isolates contained nif-gene and PGPR activity (B2, B4, B5, B6, B7 and B8) were applied to seeds, that helped in faster germination and better elongation of root and shoot. The observations were statistically significant.

Index A Abiotic stresses, 66, 76, 78, 128, 129, 132, 133, 176, 184 ACC (1-aminocyclopropane-1-carboxylate) deaminase, 32, 34, 55, 65, 66, 71-73, 75-78, 83, 94, 103, 130 Acidobacteria, 35 Acidothiobacillus, 17, 156 Actinobacteria or actinomycetes, 27, 32, 34, 35, 37, 140, 141, 215, 216 Agglomeration, 206 Agriculture, 2, 15, 19, 20, 41, 42, 43, 44, 45, 46, 48, 49, 52, 54, 58, 59, 110, 119, 120, 132, 138, 139, 141, 148, 154, 175, 176, 177, 184, 201, 202, 203, 204, 205, 206, 221, 222 Agrobacterium sp., 4, 10, 18, 32, 35, 53, 100, 121, 138, 216