Effects of flooding conditions and phytohormones on coleoptile elongation in Indica rice varieties

The unpredictable scenarios of current climate change pose great challenges for global food security. Climate change triggers submergence, a natural disaster that affects cereal production in the Mekong Delta of Vietnam. Among cereals, rice is a unique species in its ability to germinate and develop a long coleoptile under water. Several previous studies indicated that the capacity of japonica rice is better than indica rice cultivars. Herein, we assessed the ability of coleoptile elongation and the role of exogenous auxin (IAA) in promoting rice coleoptile length under dark, flooded conditions using 20 indica rice varieties collected from the Mekong Delta. We germinated 20 rice seeds per variety under water (with and without adding auxin at different concentrations) for several days and measured the coleoptile length at two different timepoints of submergence. We found that the ability to develop a long coleoptile under water was not related to the rice subspecies. The average coleoptile length at day 8 and the growth curve from the beginning to day 8 of the submergence experiment of our rice cultivars were the same. We also found that 10 μM of IAA concentration expressed a significant effect on the capacity of coleoptile elongation in both long and short coleoptile-harboring indica rice subspecies. Our results suggested that OM108, OM5451, and ĐT8 are promising rice cultivars for rice production in the Mekong Delta of Vietnam.