Exploiting beneficial traits of plant-associated fluorescent pseudomonads for plant health

Abstract

Plants have recently been recognized as meta-organisms harboring distinct microbiome and reveling close symbiotic relationship with the associated microflora. Each plant has a unique niche and possesses species-specific microbes to a certain proportion and majority of the ubiquitous microbes that fulfill important host as well as ecosystem function. Currently, agricultural crops are facing challenges due to imbalance of micronutrients, deterioration of soil health, fluctuating environmental conditions, and increasing pest and pathogen attack. The rhizosphere region of the plants is the most extensively studied area due to its remarkable microbial diversity. Fluorescent pseudomonads are Gram-negative, motile, rod-shaped bacteria predominantly inhabiting the vicinity of rhizosphere and sometimes even the root interior. They effectively colonize the plant roots and rhizosphere soil because of their excellent ability to utilize a variety of organic substrates exuded by the plant roots. The study on the role of fluorescent pseudomonads in agriculture has been a matter of great interest attributable to their ability to control plant diseases, maintain soil health, and influence the plant growth directly or indirectly. They directly promote the plant growth by producing secondary metabolites such as siderophores and phosphatases that can chelate iron and solubilize phosphorus, respectively, from the soil and make them available to the plants. They also produce indole-3-acetic acid (IAA) and 1-aminocyclopropane-1-carboxylate (ACC) deaminase that sequesters ACC, the precursor of ethylene. They also indirectly promote the plant growth mainly by suppressing the plant pathogens by producing an array of antibiotics and fungal cell wall degrading enzymes. Specific metabolites produced by fluorescent pseudomonads may elicit defense reactions and induce systemic resistance of the host plants. Introduction of such multifunctional rhizobacteria to the plant roots can lead to increased plant growth and protection against phytopathogens. This chapter reviews the beneficial traits of the fluorescent pseudomonads and their relationship to the functioning in the rhizosphere. © 2017 Springer International Publishing AG.