Varietal Difference in Heat-Stress Tolerance during Hot Water Disinfection of Rice Seeds in the “NIAS World Rice Core Collection”

Abstract

Hot water disinfection method is a chemical-free agriculture technique which is gathering attention. It is conducted by immersing rice seeds in hot water at 60°C for 10 minutes. However, this condition is not always effective to prevent the occurrence of some seed-borne diseases. To establish and spread the use of this disinfection method, we need to introduce the heat tolerance trait to many cultivars and conduct the treatment under severer conditions. The heat tolerance varied with the rice cultivar. The seeds of “Hitomebore”, a Japonica rice cultivar subjected to hot water disinfection showed extremely strong heat resistance. On the other hands, the seeds of Indica and glutinous rice were relatively sensitive to heat. In the present study, to find a useful genetic resource, we analyzed the varietal difference in heat-stress tolerance during the hot water disinfection of rice varieties include in “NIAS world rice core collection”. The result showed that the seeds of two Japonica cultivars: “Rexmont” and “Tupa 729”, and an Indica cultivar: “Badari Dhan”, had extremely high heat-stress tolerance. In addition, we found that several Indica varieties including “Badari Dhan”, and glutinous rice cultivars had heat tolerance as strong as “Hitomebore”, and are useful as genetic resources to elucidate the gene responsible for heat-stress tolerance during hot water disinfection treatment.