FULL-LENGTH RESEARCH ARTICLE Characterization of Submerged Tolerant Elite Rice Genotypes Having Improved Physiological Traits and Oxidative Defense System grown under Rainfed Lowland Ecosystem of Eastern Indo-Gangetic Plains S. K. Dwivedi 1 • N. Bhakta 1 • Santosh Kumar 1 • J. S. Mishra 1 Received: 9 December 2015 / Accepted: 29 March 2017 Ó NAAS (National Academy of Agricultural Sciences) 2017 Abstract An experiment was conducted in 2014 and 2015 kharif season to evaluate the performance of rice genotypes under submerged condition on the basis of morpho-physiological traits and yield attributes. The study revealed that rice var. Swarna Sub 1 exhibited the highest survival (91.2%), whereas var. IR42 as susceptible check showed the least survival (4.2%) under submergence. Among the tested genotypes, IR 10F365, IR 11F216 and IR 11F239 with the respective survival values of 81.4, 80.0 and 78.1%, respectively, were found to be at par with the var. Swarna Sub 1 after 16 days of complete submergence at vegetative stage. Moreover, physiological traits like chlorophyll, sugar content and anti-oxidative system (SOD and CAT) were higher in tolerant genotypes as compared to susceptible ones. Less reduction in the content of sugar, chlorophyll, SOD and CAT activity was observed in genotypes IR 10F365, IR 11F216 and IR 11F239 along with var. Swarna Sub 1 (tolerant check) after submergence, while in susceptible genotypes IR 09L311, IR 08L216 and IR 55423-01 the reduction in sugar and chlorophyll content was higher just after submergence. Apart from physiological traits, tolerance genotypes have higher yield and yield attributing character as compared to susceptible genotypes. Thus, the study revealed that not only var. Swarna Sub 1 even few more elite rice lines found superior in terms of submergence tolerance and yield. Keywords Elite rice genotypes Á Physiological traits Á Submergence tolerance Á Yield attributes Introduction Among the biotic and abiotic stresses affecting rice pro- duction, submergence has been identified as the third most important constraints for rice productivity in eastern India [13]. Continuous submergence affects over 15 mha of rain- fed lowland rice areas [16]. Prolong submergence caused annual losses of $650 million to $1 billion in Asia [8]. Lowland rice is typically cultivated in paddies of 5–25 cm of standing water, which are highly vulnerable to monsoon flash floods of 50 cm or more that can rapidly and completely submerge plants. However, flash flooding can cover the entire plant for prolonged periods, and most rice cultivars die within 7 days of complete submergence [2, 26]. Rice pro- ductions in these ecosystems depend mainly on monsoon rainfall and runoff water from the catchment areas [27]. The average rice productivity of this ecosystem is only 1.2 t ha -1 in normal condition and hardly 0.5 t ha -1 in submergence [25]. Eastern India alone has approximately 10 million ha of rice lands affected by flash floods and complete submergence with poor drainage [20, 21]. The main constraint for rice production is a lack of suitable high-yielding variety (HYV) that can tolerate complete submergence and have good grain quality [24]. Submerged plants faced deficit conditions for light, gas diffusion, soil nutrients, mechanical damage which invites attack of diseases and pests [17]. The carbohydrate content of plants was found to be significantly and positively Electronic supplementary material The online version of this article (doi:10.1007/s40003-017-0258-6) contains supplementary material, which is available to authorized users. & S. K. Dwivedi sharad.dwivedi9736@gmail.com 1 Division of Crop Research, ICAR Research Complex for Eastern Region, Patna 800014, India 123 Agric Res DOI 10.1007/s40003-017-0258-6