1. Microbial Signaling in Plant—Microbe Interactions and Its Role on Sustainability of Agroecosystems

Sustainability in agroecosystems is governed primarily by the functional balance between soil processes and plant productivity. Microorganisms are key drivers of important soil processes such as nutrient recycling, and their activity directly influences the functional stability and sustainability of the soil ecosystem. In nature, microbes tend to function as functional guilds or communities, thereby creating a complex network of microbial interactions. Therefore, microbial signalling processes play an important role in communication within a particular functional guild or among different guilds. Numerous chemical compounds acting as signalling molecules in the soil-plant system have been identified. However, the understanding of how these molecules contribute to soil ecosystem stability and sustainability through inter- and intra-species chemical signalling is incomplete. In particular, it is known that chemical inputs in agroecosystems can suppress some microbes (e.g. nitrogen fixers), which can also reduce the interactions between microbes due to destruction of the signalling networks, consequently breaking the delicate balance of the soil ecosystem. Understanding the impact of microbial signalling processes on soil ecosystem sustainability is imperative if we are to address this issue. This chapter reviews the current knowledge on the mechanisms of microbial signalling in plant–microbe interactions and technical advances in identifying signalling pathways between plants and soil and also proposes avenue for future research in this field.