Enhancing nutritional quality of pigmented rice under salt stress: the role of temperature and environmental variability
Aung Zaw Oo, Minyu Sun, Hidetoshi Asai, Koki Homma, Hiroshi Ikeura, Kaori Fujita, Khin Thuzar Win
Abstract
Salinity, worsened by climate change, poses a significant challenge to rice cultivation, affecting both yield and nutritional quality. Black rice, known for its high antioxidant content, has not been thoroughly studied under salt stress and varying environmental conditions. This study investigates the effects of salinity and temperature on black rice (variety-Asamurasaki) and white rice (variety-Hitomebore) through pot experiments and three years of field trials. The results show that salt stress negatively impacts grain yield in both varieties, with notable varietal differences in nutritional quality. Salt stress increased total phenolic, flavonoid, and anthocyanin contents in black rice, whereas white rice showed no such changes. Black rice also exhibited enhanced levels of crude protein, zinc, and iron. In the pot experiment, salt stress improved grain color parameters, enhancing black rice’s appearance. However, high temperatures caused brown spots on the grains, reducing the benefits of salt stress on appearance and nutritional content. While salt stress can improve black rice’s nutritional value, temperature management is crucial for optimal grain quality. Further research is needed to explore interactions with different black rice varieties.