The rhizosphere: a playground and battlefield for soilborne pathogens and beneficial microorganisms

Abstract

The rhizosphere is a hot spot of microbial interactions as exudates released by plant roots are a main food source for microorganisms and a driving force of their population density and activities. The rhizosphere harbors many organisms that have a neutral effect on the plant, but also attracts organisms that exert deleterious or beneficial effects on the plant. Microorganisms that adversely affect plant growth and health are the pathogenic fungi, oomycetes, bacteria and nematodes. Most of the soilborne pathogens are adapted to grow and survive in the bulk soil, but the rhizosphere is the playground and infection court where the pathogen establishes a parasitic relationship with the plant. The rhizosphere is also a battlefield where the complex rhizosphere community, both microflora and microfauna, interact with pathogens and influence the outcome of pathogen infection. A wide range of microorganisms are beneficial to the plant and include nitrogen-fixing bacteria, endo-and ectomycorrhizal fungi, and plant growth-promoting bacteria and fungi. This review focuses on the population dynamics and activity of soilborne pathogens and beneficial microorganisms. Specific attention is given to mechanisms involved in the tripartite interactions between beneficial microorganisms, pathogens and the plant. We also discuss how agricultural practices affect pathogen and antagonist populations and how these practices can be adopted to promote plant growth and health.

Defense Related Phytohormones Regulation in Arbuscular Mycorrhizal Symbioses Depends on the Partner Genotypes

“…They are frequently challenged by microbial pathogens that threaten their fitness, but they also interact with neutral or beneficial microorganisms that positively affect multiple vital parameters, such as plant nutrition, growth, and stress tolerance (Barea et al 2005;Raaijmakers et al 2009). In fact, a microbe-free plant may be considered an "exotic exception" (Partida-Martínez and Heil 2012).…”

Isolation and characterization of a new iturinic lipopeptide, mojavensin A produced by a marine-derived bacterium Bacillus mojavensis B0621A

“…5,6 Plant-associated bacteria also have the potential to improve the growth of crops as plant growth-promoting rhizobacteria. 7,8 These lipopeptides have important roles and there may be some synergistic effects in the interaction of plants, microorganisms and phytopathogens in the soil ecosystem.…”

Heavy metal tolerant Pseudomonas protegens isolates from agricultural well water in northeastern Algeria with plant growth promoting, insecticidal and antifungal activities

“…Fluorescent pseudomonads and other rhizobacteria are well known for their abilities to successfully colonize plant roots and to promote plant growth by biological control [21] and plant growth promotion activities [42]. In the present study, two Pseudomonas sp.…”

“…The isolates S4LiBe and S5LiBe are very similar (99.8% 16SrRNA gene similarity) to each other and are very closely related (99.4 to 99.7%) to the P. protegens strains CHA0 T and Pf-5 [44]. However, a definite phylogenetic clarification would need further analysis based on concatenated alignments of several household genes [30,42], because 16S rRNA analysis alone cannot conclusively resolve very closely related species, like in the Pseudomonas fluorescens cluster.…”