Exploring the efficacy of silicon supplementation on control of rice grain discoloration disease

Rice is the most important cereal crop in Sri Lanka. Grain discoloration is an emerging disease complex, reducing grain quality of rice crop. Grain discoloration control is, however, mainly focused on fungicide; their use is limited due to perceived environmental problem and health concern. Silicon (Si) application is known as encouraging eco-friendly alternative to fungicide. Foliar applications of Si-based formulations were evaluated to examine their effect on reducing grain discoloration disease. Field experiments were conducted at Rice Research and Development Institute (RRDI), Batalagoda from May to September 2017. After planting, Si was applied as solution at the rate of 1 mL/L at tillering and early flowering stage. Fungicide and control (sterilized water) were applied as treatments at early flowering stage. Treatments were arranged in a randomized complete block design with three replications. Data on plant height, total number of tillers per plant, chlorophyll content, yield, incidence of plant infection and percentage of grain discoloration were recorded. Laboratory study was carried out to isolate and identify the grain discoloration causing pathogens from the infected seeds by using potato dextrose agar plate method. Results revealed that incidence of plant infection and grain discoloration percentage were reduced by foliar application of silicon supplements as same as fungicide application. Among the Si-based formulations tested, Gainexa UPL gave the best result in controlling grain discoloration in rice. These silicon supplements could be used as alternatives to synthetic fungicide and could reduce the amount of fungicide needed during rice crop cultivation. Curvularia lunata and Curvularia pallescence were identified as the causal organisms of rice grain discoloration disease in the study area.