Beneficial Interactions in the Rhizosphere

Abstract

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 benefi ts 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 benefi t plants, namely plant growth promoting bacteria, mycorrhizal fungi and other benefi cial 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 benefi cial 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.

Distribution of phosphatase activity and various bacterial phyla in the rhizosphere of Hordeum vulgare L. depending on P availability

“…Beta-and Gamma-Proteobacteria were more abundant in the rhizosphere of the P-fertilized plants. Both classes are known to play a key role in rhizosphere colonization (Inceoglu et al, 2010;Hol et al, 2014) and are relatively fastgrowing copiotrophic microbes (Philippot et al, 2013). The control treatment showed a higher abundance of Actinobacteria and especially Firmicutes than the P-fertilization treatment, which are also known to colonize the rhizosphere (DeAngelis et al, 2009;Eastman et al, 2014;Haesler et al, 2014;Hol et al, 2014).…”

The Potential of Hyperspectral Patterns of Winter Wheat to Detect Changes in Soil Microbial Community Composition

“…We can only speculate about the mechanism behind this positive association. Microorganisms in general can help the plant with nutrient uptake, induce production of secondary metabolites, produce hormones that affect plant growth ( Hol et al, 2014 ), all of those could change hyperspectral reflectance patterns (e.g., Kumar et al, 2001 ; Ayala-Silva and Beyl, 2005 ; Ferwerda et al, 2005 ; Font et al, 2005 ; Carvalho et al, 2013a ). Soil biodiversity might benefit plants directly via changes in nutrient availability, or indirectly by offering protection against pathogens.…”

“…Live soil contains a variety of organisms, large ones like earthworms, ants, and larvae and microbial ones like protozoa, bacteria, and fungi. Some of those organisms will affect plant chemical composition, either by mutualistic effects such as providing nutrients, producing growth hormones, suppressing diseases ( Hol et al, 2014 ) or by pathogenic interactions, which damage plant tissue and could trigger the plants’ defense system ( Termorshuizen, 2014 ). Variation in the plant’s chemical composition can be detected by high-resolution spectroscopy ( Asner and Martin, 2008 ; Ramoelo et al, 2012 ; Carvalho et al, 2013a , b ; Kokaly and Skidmore, 2015 ).…”

Hemlock woolly adelgid alters fine root bacterial abundance and mycorrhizal associations in eastern hemlock

“…The 244 reduced bacterial abundance found in adelgid-infested hemlock stands may simultaneously be 245 linked to reduced ectomycorrhizal associations and changes in root and soil nutrient chemistry 246 associated with infestation. Indeed, some studies have found that soil communities experiencing 247 mycorrhizal loss also lose their fungally-associated bacteria (Hol et al, 2014). However, the 248 significant decline in absolute numbers of bacteria suggests resource limitation from the root.…”