Assessing the Effects of a Novel Copper-Based Silicon Source on Reducing Target Spot Severity: Physiological Aspects of Cucumber Plants
摘要
Target spot, caused by the fungus Corynespora cassiicola, is a foliar disease that causes significant damage to several cultivated species, particularly cucumber, where effective control remains a challenge. Thus, this study aimed to evaluate the effects of different silicon sources and doses on the severity of target spot and the physiological responses of cucumber plants. The experiments were conducted in a greenhouse, testing two silicon sources—copper silicate and potassium silicate—applied at five Si doses (0, 28, 56, 84, and 112 mg L⁻1), along with an inoculated and a non-inoculated control, totaling twelve treatments. Foliar Si applications were performed weekly as a preventive measure, starting at the two-true-leaf stage, 17 days after sowing, for a total of three applications. Plant inoculation was carried out by spraying a conidial suspension onto both sides of the fully expanded second and third definitive leaves until runoff, four days after the third silicon treatment application. Evaluations included target spot severity, leaf gas exchange parameters, biometric components, and nutrient content. Silicon application effectively controlled the disease, with Cu-Si being more efficient than K-Si. Si increased biomass production, improved plant nutrition in inoculated plants, particularly at 56 and 84 mg L⁻1, and influenced physiological responses by mitigating the impact of fungal infection on stomatal conductance, photochemical efficiency, and CO₂ assimilation. The results demonstrated that the disease reduced plant growth parameters and the accumulation of certain nutrients, whereas silicon reduced disease severity and its associated damages. It can be concluded that preventive Si application alleviates stress in cucumber plants affected by target spot by maintaining adequate photosynthetic indices and nutrient levels essential for plant development.