Beneficial Interactions in the Rhizosphere

Production of plant biomass is one of the main ecosystem services delivered by soil. The area closely surrounding the root surface, the rhizosphere, is where plants interact with soil organisms. The interaction of a plant with soil microorganisms may result in several benefits to the plant, including improved nutrient availability or uptake, protection against pests and pathogens, improved tolerance to abiotic stress and growth promotion via hormones. Those relationships between plant and microorganisms determine plants growth and competitiveness. Ultimately the microbial community may determine plant community composition and succession. In this chapter we give an overview of fungal and bacterial microbial rhizosphere species that benefit plants, namely plant growth promoting bacteria, mycorrhizal fungi and other beneficial fungi. The aim is to summarize the current knowledge on mechanisms underlying plant-microbe interaction and to discuss the role of species identity and diversity for both microorganisms and plants. For each group (plant growth promoting bacteria, mycorrhiza, other beneficial fungi) we highlight the latest developments and promising future directions. At the end of the chapter the microbial groups are viewed as part of the soil ecosystem and interactions between the groups are discussed.