Screening of Japanese rice cultivars for seeds with heat stress tolerance under hot water disinfection method

Abstract

Background and Objective: Hot water disinfection is an easy and yet effective seed disinfection technique that does not require the use of agricultural chemicals. The typical condition of this method (60EC for 10 min) is not always sufficient to kill certain pathogens; however, the application of higher temperatures represses the germination rates of several rice cultivars, especially indica. This study was conducted to obtain applicable breeding materials that are extremely tolerant under treatment of hot water disinfection to facilitate the use of this useful technique in Japan and other countries in Asia. Materials and Methods: Four modern Japanese cultivars and thirty-nine cultivars of the Japanese rice landrace mini core collection were screened under hot water treatment at several high temperature conditions (60, 65 and 70°C) for 10 min. One-way analysis of variance followed by the Tukey-kramer multiple rang test and a Student’s t-test were used for statistical analysis. Results: Germination rate results showed that ‘Koshihikari’ was the most tolerant among the four modern Japanese cultivars. Meanwhile, among the Japanese core collection, ‘Aikoku’ and ‘Nagoya shiro’ cultivated in 2013 and 2015 showed the highest germination and seedling emergence rates, which were constantly higher than ‘Koshihikari’. Conclusion: The results from this study indicate that in light of their high tolerance under the hot water disinfection method, ‘Aikoku’ and ‘Nagoya shiro’ are potential breeding materials that are fruitful for the trait introduction to other rice cultivars.