A Review on the Role of Silicon Treatment in Biotic Stress Mitigation and Citrus Production

Abstract

This paper reviews the threat of citrus pathogens during citrus production, with a focus on two pre-harvest diseases, citrus leaf spot, caused by Alternaria alternata (Fr.) Keissl. (1912) and brown rot, caused by Phytophthora citrophthora (R.E. Sm. and E.H. Sm.) Leonian, (1906) as well as green and blue mold post-harvest disease, caused by Penicillium digitatum (Pers.) Sacc. and P. italicum Wehmer, (1894), respectively. Furthermore, it reviews the role of soluble silicon, Si nutrition in biotic stress mitigation and potential mitigation mechanisms. Previous studies on the use of Si fertilizers have focused on high accumulator Si crops. These have demonstrated the potential of Si to reduce the occurrence of biotic stresses, which takes place through both physical and biochemical mechanisms. However, few studies have demonstrated the potential of Si to mitigate biotic stress in citrus, or the mechanisms involved. There is a clear need for studies on the impact of Si on various stress biochemical pathways in plants generally, and specifically for citrus due to the huge loss caused by pre- and post-harvest pathogens. This will assist in deepening our understanding of the pathophysiology which is essential to develop resistant cultivars.

Silicon enhances plant resistance to Fusarium wilt by promoting antioxidant potential and photosynthetic capacity in cucumber (Cucumis sativus L.)

“…Firstly, the deposition of Si around the cell wall fosters mechanical protection which prevents pathogen penetration. In addition, Si forms complexes with organic compounds in the epidermal cell wall which also strengthen the cell wall mechanically ( Mvondo-She et al., 2021 ). Secondly, Si induces systemic resistance by improving the upregulation of genes involved in metabolism, signal transduction, defense, and stress response against different plant pathogens ( Kurabachew et al., 2013 ).…”

Impact of Silica Addition on Alleviating Cadmium Stress: Case Studies of Three Afforestation Tree Species Seedlings in Southern China

“…For instance, Si can interact with principal components of plant stress singling systems, thereby inducing defenses against fungi [12]. The mitigation effect of Si has also been observed in a variety of plants under heavy metal stress [13,14]. Concerning abiotic stresses, many mechanisms has been proven to be involved in Si's mitigating of heavy metal toxicity: decreasing the content of bioavailable heavy metal elements in soil, reducing the uptake and translocation of heavy metal elements, stimulating the activities of antioxidant enzymes and regulating the expression of genes regulating heavy metal transportation [13,15].…”