Role of Phenolics in Establishing Mycorrhizal Association in Plants for Management of Biotic Stress

Phenolic compounds are the most significant secondary metabolites produced by plants for the defense. Arbuscular mycorrhiza fungi (AMF), obligate symbionts, are the prominent one with an expanded host range and have an important role in designing ecosystems and associated productivity. Nearly up to 70% of the vascular plants are capable to form symbiotic association with AMF. AMF are primarily dependent on the host plant for photosynthates but offer much more benefit in return for the well-being of the host. Notably, they are able to modulate the tolerance of the host plant against various types of biotic stresses like fungi, bacterial, viral, phytopathogens, herbivores and nematodes. To protect themselves from the stress, plants have modified themselves with different sensory systems which can detect biotic invasion and combat the harm it causes to growth, productivity and survival. The establishment of AMF with the plants starts with the recognition of signal molecules or mostly phenolics. Among phenolics, flavonoids are the abundant compounds which are able to accelerate the development of AMF at micromolar concentrations. In addition, strigolactones molecules are also responsible for the germination of spore and growth of hyphae in fungi. The increase in phenolics compound concentrations is effective in inducing enhanced resistance against these biotic stress agents.