Plant Growth Promotion and Biocontrol Mediated by Plant-Associated Bacteria
The rhizosphere, defined as the volume of soil under the physical, chemical and biological influences of plant roots, is a region of enormous microbial diversity and activity. This microbial activity is essential for plant nutrition and health since it fa
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Plant Growth Promotion and Biocontrol Mediated by Plant-Associated Bacteria Miguel A. Matilla and Tino Krell
Abstract The rhizosphere, defined as the volume of soil under the physical, chemical and biological influences of plant roots, is a region of enormous microbial diversity and activity. This microbial activity is essential for plant nutrition and health since it favours the uptake of nutrients by the plant and offers resistance against a wide range of plant pathogens. Bacteria are the main microbial representatives in the rhizosphere, and plant growth-promoting rhizobacteria (PGPR) stimulate plant growth by multiple mechanisms. In this chapter, we present an overview of the strategies employed by PGPR to exert their beneficial effects on the colonized plants. The direct effects of PGPR on plant growth are mainly derived from their capacity to improve the nutritional status of plants and the production of phytohormones. Alternatively, beneficial rhizospheric bacteria can also promote plant health by protecting plants against pathogens mainly through the induction of systemic resistance and the production of exoenzymes and multiple antagonistic metabolites. Here, special attention has been given to the biosynthesis and biological activities of bioactive volatiles, non-ribosomal peptides and polyketides by PGPR. Finally, the promising use of PGPR-based products as sustainable agricultural practices is discussed. Keywords Plant growth-promoting rhizobacteria • Phytohormones • Biocontrol • Induced systemic resistance • Bioactive secondary metabolites
M.A. Matilla (*) • T. Krell Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, Granada, Spain e-mail: [email protected] © Springer Nature Singapore Pte Ltd. 2018 D. Egamberdieva, P. Ahmad (eds.), Plant Microbiome: Stress Response, Microorganisms for Sustainability 5, https://doi.org/10.1007/978-981-10-5514-0_3
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M.A. Matilla and T. Krell
3.1 Introduction The term rhizosphere was first introduced by Lorenz Hiltner (1904) as the area of soil surrounding the plant root system that supports high levels of microbial activity. Currently, the rhizosphere is considered as the volume of soil that is under the physical, chemical and biological influences of plant roots, including root tissues colonized by the microorganisms (Lugtenberg and Bloemberg 2004; Lugtenberg and Kamilova 2009). It was estimated that plants release up to 40% of the photosynthetically fixed carbon through root exudates, which leads to changes in the biochemical and physical properties of the surrounding soil (Hutsch et al. 2000; Walker et al. 2003; Bais et al. 2006; Newmann and Römheld 2007; Uren 2007; Badri and Vivanco 2009). Indeed, the substantial amount of nutrients released (e.g. sugars, vitamins, organic acids and sugars, among others) supports the emergence of a complex community of organisms, including bacteria, fungi, nematodes, protozoa and algae; of which some have a major impact on plant health, gro
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