Rhizo-Deposit and Their Role in Rhizosphere Interactions Among the Plant, Microbe and Other Ecological Components for Crop Management

Abstract

AbstractRhizosphere is the most important ecological niche, which plays a vital role by acting as a connecting link between plant, soil and microbes. Rhizo-deposits are the secretions released by the plant roots in the form of root exudates, border cells of roots and other rhizo-deposits. These secretions mostly include low molecular weight bioactive organic compounds, which may attract various beneficial microbes like PGPR (plant growth promoting rhizobacteria), PGPF (plant growth promoting fungi) for their colonization and some of them also contain antimicrobial defensive compounds that repel various deleterious or plant pathogenic microorganisms. Among several forms of benefits derived from rhizo-deposits, root exudates that help in attracting and harbouring various beneficial microbes like rhizobacteria and fungal bio-agents, play a crucial role in the suppression of various soil borne plant pathogens, insect pests, nematodes and harmful microbes apart from their growth promoting activities. These PGPR, PGPF, and various microorganisms with bio-control potential exhibit excellent colonizing ability with the roots and even some of them establish symbiotic and endophytic relationship with plants. These beneficial microbes colonizing the rhizosphere zone exhibit various types of mechanisms like nutrient solubilization by supplying water and inorganic mineral nutrients in the available form to the plant. They exhibit various defence mechanisms like hyper-parasitism, competition, antibiosis and induced systemic resistance response in plants against plant pathogenic and harmful microbes. In addition to these bio-control activities, these beneficial microbes like PGPR’s and PGPF’s present in the rhizosphere region help in the enhancement of plant growth parameters like shoot and root length, shoot and root biomass, chlorophyll content, vigour, flowering, fruiting and ultimately yield of plants. They also help in alleviating several abiotic stress in plants such as water scarcity, submergence and salinity. This chapter provides the insights into, how bacterial and fungal biocontrol agents help the crop plants in combating several biotic and abiotic stresses through several morphological and phsiological changes in the crop due to application of biocontrol agents and also that how these microorganisms help plants in increasing their growth and vigour. How root exudates help in colonization of various rhizosphere-inhabiting microorganisms and how application of various organic substrates and de-oiled cakes in the rhizosphere zone help in the population build-up and establishment of these beneficial microbes in the rhizosphere zone.KeywordsAntagonistParasitismRhizospherePopulation dynamicsAbiotic stressPlant growthPlant Biomass