The emerging role of silicon (Si) has attracted a great deal of interest from researchers because of the numerous agronomic benefits of this element to plants. Indeed, silicon improves plant resistance to a range of biotic and abiotic stresses, with consequent yield increases. Furthermore, it enhances resistance in several crops of great economic importance to diseases and insect pests. Until recently, the exact nature of protective effects of silicon in plants is uncertain. To date, two major defense mechanisms due to silicon application have been documented: physical defense and biochemical defense. In this review, the interaction between silicon-treated- plants and reduced biotic stresses (disease and insect pests) incidence was explored. The current research presents the agronomic importance of silicon in plants, the control of fungal and bacterial pathogens and insect pests according to their lifestyle, and viral agents, and different mechanisms of silicon-enhanced resistance. By regrouping the data presented in this paper, a good knowledge of the association between silicon treatment, increasing plant resistance, and decreasing biotic stresses occurrence could be achieved.
The interaction between bread wheat (Triticum aestivum L.) plants and four filamentous species of the Fusarium genus (the causal agent of Fusarium head blight, FHB) was analyzed in an in vitro Petri-dish assay. Pathogenicity criteria as well as germination rate reduction, standardized area under disease progress curve (AUDPCstandard), and coleoptile length reduction were investigated in seeds and six-day-old seedlings showing a moderately level of quantitative resistance, after inoculations with 16 FHB isolates. AUDPCstandard did differentiate FHB isolates and the other two pathogenicity criteria did not. It was not possible to cluster the isolates based on their species origins because of similarity in pathogenic level among the 16 fungal isolates. Cultivar-specific pathogenicity has been detected. The values of disease incidence and disease severity involved in previous artificial head and floret inoculations showed significant correlation with AUDPCstandard: r=0.653** and r=0.559*, respectively. AUDPCstandard could be of potential use in evaluating the pathogenicity of FHB in adult wheat plants.
Authors:S. Eleawa, I. Bin-Jaliah, M. Alkhateeb, N.M.K. Bayoumy, R. Alessa and Hussein Sakr
Gastric ulcer is a common gastrointestinal disease. One suggested mechanism is increased oxidative stress. Puplished data showed that dehydroepiandrosterone (DHEA) may limit oxidative stress and lipid peroxidation.