Improvement of Tolerance to Heat Stress Given during Hot Water Disinfection of Rice Seeds by Reducing their Water Contents

Abstract

Hot water disinfection of rice seeds is a clean farming technique that does not involve harmful chemical compounds. A higher temperature would have stronger disinfecting power, but would also lower seed germination ability. Thus it is important to increase the heat tolerance of the seeds of many cultivars. In the present report, we examined the effects of reducing the water content of seeds on their heat tolerances. The water content of rough rice of “Nipponbare” and “Koganemochi” was 14.7% and 15.0% respectively, and the germination rate of these seeds after immersion in hot water at 66°C for 10 minutes was less than 90%. However, when the water content of the seeds was reduced to 9-10% before the hot water treatment, more than 90% of the seeds germinated. Such an effect of seed drying before the hot water treatment was confirmed in “Hitomebore” and brewer’s rice “Tominokaori”. These results indicate that seed drying before hot water disinfection is effective for strengthening their tolerance to a high temperature.