Plants communicate with each other through production of molecules released into the atmosphere and rhizosphere. Besides, the latest experiments demonstrated interplant communication via common mycelial networks in the soil. Common mycelial network offers a potentially more effective and directed pathway of defence compared to the aerial pathway. It has been suggested that the process of forming mycorrhizas itself prepare plant defences against multiple biotic challenges (such as insect herbivores, foliar necrotrophic fungi and mechanical damage). These networks can transport signals produced by plants in response to herbivore and pathogen infestation to neighbouring plants before they are themselves attacked. There are three possible mechanisms by which common mycelial networks enable interplant signalling, but the most common is delivery of signal molecules via cytoplasmic streaming within hyphae. The nature of the signal is unknown, but this far, the key responses of receiver plants are production of methyl salicylate and jasmonic acid signalling pathways. However, identifying the molecular structure of signals will require extremely challenging controlled experiments. The impact of common mycelial networks-based warning signals will depend on their speed and the period of time over which their effects are manifested, at least as important is the physical distance over which they can travel and how many receiver plants they can affect. Understanding the role of common mycelial network in complex arbuscular mycorrhizal fungi–crop–pest interactions is important for general understanding of ecosystem functioning. It poses a considerable challenge in designing agricultural management systems that ultimately lead to pest tolerance.
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