Functional Diversity in Rhizosphere Microbial Community: Concept to Applications

The microbial diversity attains different level of complexity with microorganisms interacting with the soil as well as with the plants. It is the cumulated interactive multilateral relationship which leads to the establishment of rhizosphere. The soil type or the plant type leads to the formation of different microhabitats varying at micrometer level. Microbial diversity can be studied in terms of species diversity, genetic diversity, and ecological diversity. The microbial activity affects and modifies the exudates and the subsequent rhizodeposition which becomes decisive in establishing the microbial community in the root rhizosphere. The functional behavior of the microbial communities which may include a group of species trait represented as an individual or species leads to the functional diversity in the rhizosphere. Functional diversity influences ecosystem dynamics, stability, productivity, nutrient balance, and other aspects of ecosystem functioning. Rhizospheric microbes are directly or indirectly associated with enhancement of plant growth or plant protection by secreting biomolecules. Thus, functionally these can be categorized as PGPR which directly promotes plant growth or those inhibiting the pathogens which are generally termed as BCA (biological control agents) and indirectly enhancing the plant growth. These functionally diverse microbial types are successfully applied to maintain sustainability of the ecosystem as are now available as biofertilizers, bioprotectants, and biostimulants. It is either a co-operative or competitive relation with the other existing microbial populations leading to the establishment of microbial habitat whereupon the functional attributes of theirs which fulfils the ecological need. The ecological dependencies on each other lead to the development of stable microbial communities in the rhizosphere.