Effect of hot water disinfection incorporated with pre-drying against rice seedborne diseases

Abstract

Disinfecting rice seeds in hot water at 60°C for 10 min has been widely used in Japan; however, bakanae disease caused by Fusarium (=Gibberella) fujikuroi has become problematic with the popularization of this method because the method is ineffective compared with chemical disinfectants. Recently, pre-drying seeds to reduce seed water content to below 10% was found to improve seed tolerance to heat stress and permit the disinfection at a high temperature of 65°C for 10 min; however, the effect on disease control was not evaluated. In this study, we thus examined whether the combined pre-drying seeds and hot water treatment at 65°C for 10 min improves control of several major seed-borne diseases such as bakanae, blast, bacterial grain rot and bacterial seedling blight. The combined treatment was more effective than hot water disinfection at 60°C 10 min in controlling bakanae disease in the experiment using naturally infected seeds. The combined treatments were especially more effective than other popular methods to control the two bacterial seed-borne diseases. These results indicate that pre-drying seeds before the 10-min 65°C hot water treatment is a practical, effective method to disinfect rice seeds.