"Rice (Oryza sativa L.) is grown across the globe and consumed by approximately 3billion people or round 50% of the world population. Rice was grown on 162 million hectares and its global production was 755 million tons in 2019 (http://www.fao.org/ faostat/en, accessed on 29 June 2021). The world population may rise anywhere from 9.7 to 11 billion in 2050 (https://population.un.

org/wpp/, accessed on 29 June 2021); thus, a significant increase in rice yield will be required to feed the growing population. Flooding is undoubtedly the third most vital constraint for achieving high productivity, after heat and drought, that is affecting crop production. Seasonal and unseasonal crop damage due to the occurrence of severe flooding amounts to billions of dollars in yield losses annually. The development of rice varieties that can germinate and emerge in flooded soils will therefore help reduce the hazards of early floods, to which rice is very sensitive, and this also provides an efficient means for weed control through early flooding. Generally, stagnant flooding occurs as a result of heavy rain, which can be deep-water flooding or flash flooding. Under deep-water flooding, plants increase their stem length (internode) to escape the submergence. However, after the flood subsides, affected plants are prone to lodging and eventually this leads to death due to the exhaustion of reserved nutrients within few days. Contrarily, during flash flood, plant growth is restricted and resumes after occurrence of the flood.

Recently Sub1 gene had been identified in Sub1A-1 varieties of rice and biotechnological processes being under taken to provide Mega varieties with Sub1 characters to fit with diverse waterlogged and submerged condition for higher grain yield"--.