Plant-Microbe Interaction to Improve Soil Health

The rhizosphere constitutes an ideal example to study the natural interdependence of biological and physical factors. Health of this biologically active unit determines the stability of most ecosystems. Multiple factors like microbial diversity, plant species, existing positive and negative interactions, and diverse physical factors like nutrient availability, pH, temperature, water, etc. regulate fitness of the rhizosphere. For example, different soil types can support different plants or microbes and therefore have differences in biochemical diversity. All plant-microbe or microbe-microbe or microbe-plant-microbe interactions, in reverse, also determine the soil quality in long term and hence affect sustenance of either a natural ecosystem or, in case of agricultural lands, the crop productivity. As far as the importance of these biological interactions is concerned, especially of plant-microbe interactions in agriculture lands, it is undeniable that we are dependent on them. However, a detailed understanding of these interactions and the intricate mechanisms involved is still lacking. This chapter focuses on several such interactions known in nature that are responsible for improvement of soil quality or can be used for agricultural sustainability. We discuss several positive and negative interactions and their overall impact on crop yields. We highlight chemoattractants of different classes, which make the basis of plant-microbe associations and emphasize the missing links where future research should be focused. A special emphasis is on two explicit examples: (1) a tripartite communication between plant, fungi, and plant-pathogenic nematodes and (2) nitrogen-fixing symbiotic microbes in different plant species. Both examples strongly emphasize the use of natural means for either biological control of plant pathogens or for soil fertilization. Commercialization and further investments into the discussed and other related green methods have implication for improving soil quality and crop sustainability with minimal environmental impact.