Silicon fertilizers inciting plant defence against pathogenic fungi

Silicon (Si) is the second most abundant element on earth's crust after oxygen. It is present abundantly in the soil and is taken up by plant root in the form of silicic acid. It is most prevalent in plants of Gramineae and Cyperaceae families. A number of translocators such as LSi1, LSi2, and LSi6 are involved in Si uptake by root and its translocation in shoot. Si generally helps the plants to combat against a number of biotic and abiotic stresses. It plays an effective role in plant defence by enhancing resistance against diseases and pests. In this review an extensive study has been carried out to evaluate the role of Si in plant defence against pathogenic fungi. Si can induce resistance against pathogenic fungi through formation of physical barriers that can inhibit the fungal penetration. Si can also trigger biochemical defence by activating systemic signals like SA, JA or ET inside the plant cells. This post elicitation intercellular signalling system causes expression of defence related genes leading to hypersensitive response, structural modifications of cell wall, synthesis of antimicrobial substances like phytoalexins, defence related enzymes, phenolics and PR proteins. Application of Silicon fertilizers as soil treatment or foliar spray are found to be effective in controlling a number of plant diseases caused by fungi in the field and thus they can be used as an alternative to chemical synthetic fungicides. This study indicates the positive role of Si in plant defence response and also emphasizes on the eco-friendly approach of using silicon in plant disease management.