Optimization of Temperature Regime to Screen Cold Tolerant Rice Seedlings

Low temperature stress at the seedling stage of rice is an important factor causing the leaf discoloration, wilting and consequently leads to non-uniform crop maturation. In order to screen the cold tolerance elite lines efficiently, the five cold treatment conditions with different water and air temperature were designed and treated at seedling stage. For the evaluation of seedling tolerance, the injury was scored by visual rate and measured by Soil and Plant Analyzer Development (SPAD) meter. In the reactions of varieties for each treatment, the treatment ‘B’ condition, 12oC mean water with 24oC mean air, shows clear discoloration, so it’s correlation coefficient was highest (r=−0.9, P＜0.0001) among the treatments. In the treatment condition for screening the cold-tolerance elite line, the cultivar, treatment and their interaction significantly affect the SPAD value. The ‘A’ treatment, 12oC mean water with 34oC mean air, was the best way to observe the variation between the elite lines. On the basis of the Duncan’s test for SPAD value of cultivars, Keumo (moderate tolerant), Saetbyeol (sensitive) and Seolak (tolerant) were selected as check varieties. To study its impacts at the paddy field, the changes of crop characteristics such as height, panicle length, number of tiller and heading were investigated. In later growth period, the seedling treatment impact at the paddy field leads to heading delay. Due to the low temperature stress at the seedling stage induced by 12oC mean cold water, Japonica and Tongil group shows the heading delay 4 to 7 and 8 to 11 days respectively.