Role of Plant Growth Promoting Microorganisms in Sustainable Agriculture and Nanotechnology

Ajay Kumar, Amit Kishore Singh, Krishna Kumar Choudhary

• Publisher: Woodhead Publishing
• Year: 2019
• Print ISBN: 9780128170045
• eBook ISBN: 9780128170052
• Topic: Technology & Engineering
• Subtopic: Biotechnology
• Index: Technology & Engineering

Role of Plant Growth Promoting Microorganisms in Sustainable Agriculture and Nanotechnology explores PGPMs (actinomycetes, bacteria, fungi and cyanobacteria) and their multidimensional roles in agriculture, including their increasing applications in sustainable agriculture. In addition to their traditional understanding and applications in agriculture, PGPMs are increasingly known as a source of nano-particles production that are gaining significant interest in their ability to provide more economically, environmentally friendly and safe technologies to crop growers. The book considers new concepts and current developments in plant growth, thus promoting microorganisms research and evaluating its implications for sustainable productivity. Users will find this to be an invaluable resource for researchers in applied microbial biotechnology, soil science, nano-technology of microbial strains, and industry personnel in these areas. - Presents basic and applied aspects of sustainable agriculture, including nano-technology in sustainable agriculture - Identifies molecular tools/omics approaches for enhancing plant growth promoting microorganisms - Discusses plant growth promoting microorganisms in bioactive compounds production, and as a source of nano-particles

1

Plant growth-promoting microorganisms in sustainable agriculture

Anand Pandey¹, Arpita Tripathi¹, Piush Srivastava¹, Krishna Kumar Choudhary² and Anupam Dikshit¹, ¹Biological Product Lab, Department of Botany, University of Allahabad, Allahabad, India, ²Centre for Plant Sciences, School of Basic and Applied Sciences, Central University of Punjab, Bathinda, India

Abstract

The continuous increase in the human population is creating too much stress on existing resources of food, fuel, and raw materials. To meet the demand, agriculture practices are using intensive amounts of chemical-based fertilizers and pesticides, which ultimately leads to land degradation and biodiversity loss. Microbes associated with plants can be used to overcome problems related to soil salinity, fertility, degradation, and habitat loss. The application of several microbes—like the plant growth-promoting microorganism cyanobacteria and the mycorrhizal fungus—in agricultural practices has shown to be beneficial for plant growth and development. These microorganisms are also useful for land reclamation. This chapter discusses the benefits of utilizing beneficial soil microbes (BSMs) in the agriculture sector to maintain crop productivity along with the fertility of soil. Additionally, the ways in BSMs can be used for the sustainability of the environment is also discussed.

Keywords

Sustainable agriculture; biofertilizer; plant growth-promoting bacteria (PGPR); growth promotion

1.1 Introduction

The increasing human population is creating too much stress on existing resources of food, fuel, and raw materials. To meet the demand, agriculture practices are using intensive amounts of chemical-based fertilizers and pesticides that ultimately lead to land degradation and biodiversity loss (Carsten and Mathis, 2014). In many developing countries, the economic and self-employment sectors, agriculture plays a pivotal role (Gindling and Newhouse, 2012). According to one estimate, the average loss in crop production limits to USD 10 billion annually in developing Asian countries, the primary cause being land degradation (Lal et al., 2010). Several factors have been found to be responsible for degradation of soil. Among them, consequences due to anthropogenic activities are among the most cited in land degradation. Land degradation results in exhaustion, salinization, and desertification of soil (Kesavan and Swaminathan, 2008). The ever-advancing fields of science have provided many technological inventions for the improvement of crop productivity, but there is still global demand for food to meet the world’s population. Microbes associated with plants can be used to overcome problems related to soil salinity, fertility, degradation, and habitat loss. Living among the wide variety of living fauna present in active soil microbial entities are unique as they are directly involved in enhancing soil fertility and growth and promotion of plants while lowering biotic and abiotic stresses (Glick, 2010). According to one estimate, thousands of bacterial species and millions of fungal species can be found in one gram of soil (Blackwell, 2011), of which the majority are considered to be beneficial for both plants and soil. This chapter is a summary of the role of beneficial soil microbes (BSMs) including mycorrhizae and cyanobacteria in sustainable agriculture. The BSMs that can be utilized in the sustainability of the environment are also discussed.

1.2 Beneficial soil microbes

The soil is an active part of the lithospheric zone on Earth. It acts like a physical covering that naturally surrounds the earth surface and represents the border between all living and dead geological matter, water resources, and the cavities—in the form of gaseous pores—holding the latter two matters, thereby laying the foundation of all terrestrial ecosystems (Aislabie Jand and Deslippe, 2013). BSMs enhance plant growth by improving nutrient uptake, forming complex soil matrices, and helping in plant defense response through secretions of various metabolites. In addition, BSMs can improve tolerance of adverse environmental conditions such as salt stress, drought stress, weed infestation, nutrient deficiency, and heavy metal contamination. Recently, researchers have found that soil microbes play both beneficial and harmful roles in the soil ecosystem. However, BSMs have gained attention not only for their plant growth-promoting attributes, but also for their role in the decomposition of organic waste and detoxification of toxic substances such as pesticides and in alleviation of soil stressors (Aislabie Jand and Deslippe, 2013; Ma et al., 2016). Their direct interaction with the plant’s root system results in nutrient and mineral uptake from the decomposed soil organic matter and also helps in plant-growth promotion as well as in suppression of phytopathogens (Nihorimbere et al., 2011). Soil also contains harmful microbes that invade or parasitize plants and reduce productivity. The presence of BSMs makes soil healthier and suppresses growth of unhealthy soil microflora.

1.2.1 Cyanobacteria

Cyanobacteria are photosynthetic prokaryotes and are ubiquitous in nature. They are found commonly in lakes, ponds, springs, wetlands, streams, and rivers. Additionally, cyanobacteria are also an important component of soil (Singh et al., 2016a,b). Fritsch (1907) first noticed the loads of cyanobacteria in rice fields. Cyanobacteria is important in the maintenance of rice-field fertility due to N₂ fixation, making them a suitable natural source for soil fertility enhancement (Song et al., 2005). Free-living or symbiotic blue green algae (BGA) have a long-documented history in sustainable agriculture. According to Smil (1999), free-living cyanobacteria or symbiotic cyanobacteria (like with the water fern, Azolla) fix 4–6 billion kilograms of N₂ annually. Efficient N₂-fixing cyanobacteria like Nostoc, Anabaena, Aulosira, Calothrix sp., etc., have been recognized in different diverse agroecological regions and applied to enhance rice production (Prasad and Prasad, 2001). The use of cyanobacteria in rice fields has been in practice for a long time, but recently their use with other crops has also been tested. Cyanobacteria not only contribute in global N₂ supply, but studies also find them to be involved in phytohormone production in free-living and symbiotic associations. For example, Nostoc, Chlorogloeopsis, Calothrix, Plectonema, Anabaena, Cylindrospermum, and Anabaenopsis have been shown to be associated with the production of indole acetic acid (IAA) in the soil rhizospheric zone in paddies and wheat fields (Karthikeyan et al., 2007; Manjunath et al., 2011). Cyanobacteria also help in the soil formation process, as during their growth they excrete certain biomolecules. (Kaushik, 2014; Rosa and Philippis, 2015). Some reports indicate that cyanobacteria can grow successfully in saline soil where most plants (except halophytes) fail to grow and help to increase the fertility of such soils (Singh and Dhar, 2010).

1.2.2 Plant growth-promoting rhizobacteria

Plant growth is facilitated by microbes present in the rhizosphere (Kloepper and Schroth, 1978; Lugtenberg and Kamilova, 2009; Mishra and Arora, 2012; Ahemad and Kibret, 2014; Goswami et al., 2016). PGPR species like Azospirillum, Rhizobium, Azotobacter, Arthrobacter, Bacillus, Pseudomonas, etc., are some bacterial varieties that have the capability to enhance the fertility of soil and the growth of plants (Cheng, 2009; Mishra and Arora, 2012; Arora, 2015). Recently, additional research has been done to reveal the mechanisms of plant–microbe interactions (Beneduzi et al., 2012). The growth promotion route involves the phytohormone production, nitrogen fixation, siderophore production, solubilization of inorganic substances (P, K, Zn etc.) and making it conveniently available to the plants. From another point of view, the indirect route can be seen in the form of growth-inhibition activity against phytopathogens by one of several mechanisms, such as antibiotic or antifungal metabolite(s) production, iron depletion from the rhizosphere (as a result of chelation), induced systemic resistance (ISR), and production of wall-degrading enzymes such as chitinase (Vejan et al., 2016a,b). In addition, PGPR are also recognized as potential microbes that can protect plants from various environmental stresses in normal as well as stressed environments (Khare and Arora, 2011; Kang et al., 2014). There is strong evidence that supports the efficacy of PGPRs in sustainable agriculture, though initially the role o...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• List of Contributors
• 1. Plant growth-promoting microorganisms in sustainable agriculture
• 2. Microbes as a novel source of secondary metabolite products of industrial significance
• 3. Modern molecular and omics tools for understanding the plant growth-promoting rhizobacteria
• 4. Role of microbially synthesized nanoparticles in sustainable agriculture and environmental management
• 5. Sustainable agriculture and benefits of organic farming to special emphasis on PGPR
• 6. Plant growth-promoting microbes for abiotic stress tolerance in plants
• 7. Legal issues in nanotechnology
• 8. Applying nanotechnology to bacteria: an emerging technology for sustainable agriculture
• 9. The role of fungus in bioactive compound production and nanotechnology
• 10. Role of actinomycetes in bioactive and nanoparticle synthesis
• 11. Cyanobacteria as a source of nanoparticles and their applications
• 12. Biosynthesis of nanoparticles and applications in agriculture
• 13. Trichoderma-mediated biocontrol and growth promotion in plants: an endophytic approach
• 14. Fungal endophytes: potential biocontrol agents in agriculture
• Index