Potassium silicate treatment enhances natural disease resistance in <i>Capsicum annuum</i> L. and reduces anthracnose disease development

The study investigated the possibility of enhancing natural disease resistance (NDR) of chili (Capsicum annuum L.), cvs. HYW and CA8, against anthracnose disease, using potassium silicate (Kasil®) as a soil drench or postharvest spray treatment. Anthracnose disease in chili, in this study, was shown to be caused by Colletotrichum acutatum. Potassium silicate (Kasil®), applied as a postharvest spray to the fruit of either cultivar, at 100, 200 and 400 mg/l, reduced anthracnose development significantly (p = 0.05) when the fruits were challenge-inoculated 3 days after treatment. Treatment was slightly more effective at 200 mg/l. There was 100% of reduction of anthracnose in treated fruits of cv. CA-8 throughout an 8th day period of storage following fruit inoculation. In the cv. HYW, the same treatment showed 100% disease reduction only initially, 4 days after inoculation. The treatment was also applied as a pre-harvest soil drench commencing from flower initiation, at 200 mg/l, weekly for 4 weeks. The treatment reduced anthracnose disease significantly (p = 0.05) in harvested fruits, challenge-inoculated with C. acutatum. Spore germination assay revealed that potassium silicate had no antifungal effect to C. acutatum. Potassium silicate (Kasil®)-treated fruits, inoculated with C. acutatum after harvest, showed greater accumulation of phytoalexins and increased level of β-1, 3-glucanase in fruit tissue.