eChapters

Phosphorus is one of the essential nutrients for plant growth. It is an integral part of the cellular activities of the living organisms. It has a defined role in plant metabolism such as cell division, development, photosynthesis, break down of sugar, nutrient transport within the plant, transfer of genetic characteristics from one generation to another and regulation of metabolic pathways. Phosphorus is a frequently limiting macronutrient next only to nitrogen for plant growth and makes up about 0.2% of plant dry weight. The plants obtain their P requirement from the soil pool. It occurs in soil as inorganic phosphates, produced by weathering of parent rock or as organic phosphate derived from decayed plant, animal, or microorganisms.

Nitrogen is the most important element on which depends growth and productivity of plants. It is also the most abundant molecule in the atmosphere (80%), yet it cannot be utilized by plants. The plant utilizable form of nitrogen is either, its most oxidized form, the nitrates or the most reduced state, the ammonia.  The indiscriminate use of nitrogenous fertilizers amounts to depletion of non-renewable fossil fuels used in fertilizer production. Sustainable agriculture depends largely on renewable resources and on-farm nitrogen contributions are achieved largely through biological nitrogen fixation (BNF), which helps in maintaining and/or improving soil fertility by using atmospheric nitrogen. Annually BNF is estimated to be around 175 million tonnes of which close to 79% is accounted for by terrestrial fixation.

The term soil refers to the outer, loose material of the earth’s surface, a layer distinctly different from the underlying parent rock. A number of features characterize this region of the earth’s crust. It is the natural medium, which supports plant growth. It provides the physical support needed for the root system and also supplies nutrients needed for plant growth. It is a perennial source of organic matter. It supports a vast population of microorganisms.

Biotechnology plays a very important role in agriculture as a result of its ability to modify microorganisms, plants, animals, and agricultural processes. The umbrella of microbial technology in agriculture covers numerous scientific activities, ranging from production of biofertilizers to that of microbial pesticides; from biological nitrogen fixation to lignocellulose degradation; from production of biomass and biofuels to transgenic plants. Terrestrial ecosystem contains an important dynamic living matrix termed soil, which is critical for agricultural production and food security. Soil forms the medium for growth and maintenance of a variety of plant species. Soil is considered a store house of microbial activity, though the space occupied by living microorganisms is estimated to be less than 5% of total space.

Abstract

Microbiological synthesis of nanoparticles has emerged as rapidly developing research area in nanotechnology across the globe with various biological entities being employed in production of nanoparticles constantly forming an impute alternative for conventional methods. Simple prokaryotes to complex eukaryotic organisms including higher plants are used for the fabrication of nanoparticles. In the present article, the synthesis of important plant nutrients like Mg, Zn, Ag, Au, Ti, P and Fe nanoparticles from different fungal species, their characterization and application potential of nanonutrients in agriculture is elaborately discussed.

Abstract

Microorganisms inhabiting in the rhizosphere play a vital role in ecosystem functioning. Rhizosphere is an area around the root surface where pathogenic and beneficial microorganisms repose and influence the plant growth and health. These microbial groups of bioagents found in the rhizosphere include bacteria, fungi, nematodes, protozoa, algae and micro-arthropods. Because of their rich diversity, complexity of interactions and numerous metabolic pathways, microbes are an amazing resource for biological activity. These microorganisms require organic matter for their growth and activity in soil and provide valuable nutrients to the plants and hence maintaining the plant health. The most promising fields for the use of bioinoculants are agriculture, horticulture and forestry. There are many reports on the inoculation of bioagents in agriculture and horticulture crops but only a few reports are available in forestry. This article is an overview on various bioinoculants which are used during inoculation and a compilation of scattered reports of bioinoculants in forestry only.

Abstract

Amongst various oilseed crops grown across the world, soybean (Glycine max L. Merrill) is globally important as a high source of protein and oil for human consumption and is also being used as potential feed for animals. Soybean is grown under rain-fed conditions in the tropics and subtropics in the marginal lands with less amount of external application of chemical fertilizers. The frequent climate variations have created a number of biotic and abiotic stresses, drought being a major abiotic stress which adversely affects the soybean productivity. Thus, to enhance the productivity of soybean, besides managing the nutrients, stress management is of utmost importance. There is a great opportunity of application of microbes especially arbuscular mycorrhizal fungi (AMF) where its application alone or in combination with plant growth promoting rhizobacteria (PGPR) can help in nutrient mobilization and remediation of plant stresses.

Abstract

Soil salinization is an important factor limiting crop production, mainly in the arid and semiarid regions of the world. Nevertheless, plants naturally have evolved several physiological, biochemical and molecular mechanisms to establish and thrive in salt stressed soils. In addition to breeding crops for salt tolerance, recent emphasis is on exploring the possible role of plant-microbe interactions in amelioration of salt stress in plants. It is now well established that arbuscular mycorrhizal (AM) symbiosis alleviates the effect of salt stress in plants. Further, available evidence does suggest that AM symbiosis regulates many of the plant’s salt stress alleviation mechanisms. However, the molecular basis for many of these mechanisms is yet to be ascertained. In this chapter, we summarize the current knowledge on the role of AM symbiosis in alleviation of salt stress in crop plants, which now appears to be a promising strategy to improve crop yield in salt stressed soils.

Abstract

Abiotic stresses lead to the overproduction of reactive oxygen species (ROS) in plants which are highly reactive and toxic and cause damage to proteins, lipids, carbohydrates and DNA which ultimately results in oxidative stress. The arbuscular mycorrhizal fungi (AMF)-symbiosis can confer a greater degree of tolerance against drought stress in many cash crops. The significance of heat shock proteins (Hsps) and chaperones in abiotic stress responses in plants, and co-operation among their different classes and their interactions with other stress-induced components is well known. Soil salinity is a major abiotic stress adversely affecting plant growth and crop production worldwide. Phyto-mycoremediation utilizing AMF as plant inoculants is regarded as a promising strategy to heavy metal pollution remediation. Plants have stress specific adaptive responses as well as responses which protect the plants from more than one environmental stress. The potential of phytoremediation of contaminated soil can be enhanced by inoculating hyper-accumulator plants with mycorrhizal fungi most appropriate for the contaminated site.

Abstract

Drought and salinity are two major abiotic stresses that affect various aspects of human lives of one third world population including human health and agricultural productivity. Abiotic stresses such as salinity, drought, nutrient deficiency or toxicity, and flooding limit crop productivity world-wide. A living organism is considered resistant if it tolerates a given physicochemical stress. The presence of microorganisms within the soil, specially a main group known as arbuscular mycorrhizal fungi (AMF), is a key factor in the adaptation of plants to the different ecosystems. The AMF colonizing within the plant roots can determine the success of plants in salt- and/or drought-affected areas. The symbiosis with AMF has been proposed as one of the mechanisms of salinity and water stress avoidance. Studies have shown greater drought and salinity tolerance in AMF-colonized plants by a number of mechanisms. These mechanisms include enhanced water and nutrient uptake directly by extraradical hyphae, higher leaf stomatal conductance and/or better root system architecture, higher capacity of osmotic adjustment and antioxidant defense systems, better soil structure due to higher glomalin and over expression of genes encoding antioxidant enzymes.

Abstract

A majority of the plants studied in natural ecosystems are symbiotic with microorganisms that either reside entirely (endophytes) or partially within plants. These microorganisms express different associations ranging from mutualism to parasitism. These symbiotic relationships appear to impart tolerance to various types of abiotic stresses such as heat, drought, salinity, heavy metals, etc. and sometimes may be responsible for the survival of both plant hosts and microbial symbionts in high stress habitats. The amelioration of the abiotic stresses by the endophytes assumes increasing significance in the light of rapidly changing global climate, which is likely to face frequent incidences of extreme weather conditions like high temperature, droughts, etc.

Abstract

Variously defined endophytes are highly diverse in plants in natural ecosystems, and most of them are symbiotic with of them are Asymptomatic presence of endophytic fungi in internal tissues on healthy host plants are able to play vital roles in physiology and biochemical processes. As a result of this interaction endophyte produces chemical substances having various applications. This chapter provides a brief review of certain grass and non-grass endophytes capable to extend beneficial impacts on host plants to sustain the unfavourable conditions of abiotic stresses. However, biotic stresses are also a matter of great concern, where endophytes can play important roles in combating the unfavourable situation. Endophytic fungi used in bio-control and other agriculture related sectors are also  highlighted in this review. Endophytic fungi producing volatile organic compounds reported from all over the world and their various applications find place in this article which has opened new frontiers of bioprospecting of endophytic fungi.

Abstract

Microbes are endowed with a high and exploitable potential of being useful associates with their surrounding environment and host in case of symbiotic relationship. Most of the microbes live alone but many of them require association of other living system for its survival. Hence, the beneficial role of microbes is always correlated with growth promotion and survivability of other associated living system. Now it is established that microbes play an important and key role in plant growth and development, even its survivability in case of symbiotic mycorrhizal association with orchids. They are nothing but potential tool protecting plants from different adverse conditions like diseased state, environmental stress like cold temperature, drought, metal contamination, salt and acidic or alkaline stress.

Abstract

In its natural environment, a plant faces various types of stressors. In fact, stress in moderation is a welcome event in plants. Only when it is in excess, would it compromise the productivity of plants. Beyond a threshold, stress (biotic and abiotic) has a detrimental effect on plant growth causing extensive yield losses in crop plants worldwide. Plants being sessile, have evolved a complex set of mechanisms to perceive the changes in the environment. Plants respond to minimize the potential damage due to stress while simultaneously preserving resources vital for their growth and development. The chapter presents an overview of various types of biotic and abiotic factors that act as plant stressors and the mechanisms by which plants respond to these stresses. The chapter concludes with a perspective on how the plant’s innate stress response machinery can be exploited for achieving higher tolerance to stress in crop plants.

Abstract

Impact of climate change and related stresses on plant productivity are being witnessed worldwide with developing countries being more vulnerable due to more dependency on agriculture. Microorganisms can play important role as economic and farmer’s friendly strategy to combat abiotic stress in agriculture. A wide range of microorganisms associate with plants, and many of them confer beneficial effects to their hosts through different mechanisms like production of growth promoting substances, nutrient acquisition, protection against plant pathogens etc. In the last few decades, role of microorganisms in imparting tolerance to plants against different abiotic stress has been reported in many crop plants. Under stresses conditions, plant-microbe interactions become more common towards coping with the stress. Selection and application of efficient abiotic stress tolerant microorganisms can be a fruitful strategy to alleviate negative effects of abiotic stresses in plants.

Abstract

With increasing population and subsequent human requirements; the generation of municipal solid waste (MSW) has increased all over the world. In India, the safe disposal of the municipal solid waste still remaines a problem for the authorities concerned. Depending upon the nature and type of the MSW, there are physical and chemical methods for the disposal of the waste, but these methods have their own limitations. Those limitations may be overcome by biological methods. Higher number of microorganisms are present in MSW which may either be pathogenic or nonpathogenic. These microorganisms may play a vital role in bioconversion of MSW into compost. The compost thus produced is useful in increasing soil fertility and reducing the concentration of the waste.

Abstract

The rhizomicrobiome plays a vital role in maintaining plant health and is highly influenced by the root exudates of the host plant. Plants select a subset of microbes at different stages of their development, and determine the microbiome community composition in its immediate vicinity presumably for specific functions. The rhizomicrobiome is composed of diversified microbial community with specific functions and is highly influenced by the plant type, soil type and environmental conditions. The rhizomicrobiome communities apart from promoting plant growth also elicit induced systemic tolerance to salinity and drought in stressed plants. Bacterial communities producing 1-aminocyclopropane-1-carboxylate (ACC) deaminase modulate stress ethylene in plants and alleviate the effects of abiotic stress and increases plant adaptability to stressed environment.

Abstract

Ever growing population and associated food scarcity are the major issues of concern globally. Microorganisms are the ultimate solution for addressing this severe problem in association with recent advances made in genomics and molecular biology. Many bacterial and fungal species which are in association with plant rhizosphere soil can immensely contribute in better growth and developments, ultimately leading to better yield. Exploring these novel organisms happens to be the need of an hour. Metagenomics and next generation sequencing technologies can contribute in identifying those microbes which are otherwise impossible to cultivate traditionally.

Significant transformation took place in the traditional variety improvement and seed production programmes in the sixties and modernized with initiation of hybrid development programme in maize, sorghum and pearl millet, as well as with the introduction, breeding and release of semi dwarf high yielding varieties of wheat and rice. To support the release of varieties and their quality seed production Indian Parliament enacted Indian Seeds Act in 1966. Subsequently, National Seeds Corporation was launched by Government of India for scientific growth of seed industry in the country. All these developments led to the green revolution and country attained self-sufficiency in food crops.

Two decades after India’s independence, during the 1960s, the formal seed sector in India was dominated by the Public sector. It was in 1961 that the National Seeds Corporation (NSC) was established under the Ministry of Agriculture and was at the centre of seed production of breeders, foundation and certified seeds and their quality control. In furtherance of their control in the seeds sector, the National Seeds Project (NSP) was undertaken by the Indian Government in 1967 along with the assistance of the World Bank. In the sixties, the traditional crop breeding and seed production programmes were significantly transformed and modernized with initiation of hybrid development programme in maize, sorghum and pearl millet and introduction, breeding and release of semi dwarf high yielding varieties of wheat and rice.  Indian Seeds Act was enacted in 1966 ensuring official release of varieties and their quality seed production