Post-germination seedling vigor under submergence and submergence-induced SUB1A gene expression in indica and japonica rice (Oryza sativa L.)

We evaluated post-germination seedling vigor in indica and japonica rice under submergence based on shoot elongation and recovery after submergence. The japonica cultivars showed more vigorous shoot elongation than indica cultivars under submergence in the dark, whereas an opposite response was observed under the light-dark submergence. Both Nipponbare and FR13A that are respectively known as submergence intolerant and tolerant cultivars showed vigorous shoot growth under submergence and high recovery after the stress, irrespective of the light/dark conditions. The results show that vigorous shoot growth enables rice seedlings to escape and survive submergence stress. RT-PCR analysis showed that expression of SUB1A, which is known as a key gene controlling submergence tolerance, was induced in elongating seedlings of FR13A and other indica cultivars including floating rice under submergence with light illumination. Our results suggest that light-induced SUB1A gene expression does not hinder the shoot elongation response under submergence in rice at the post-germination seedling stage.