Abstract
Complete submergence up to 1-2 weeks of low land rice crops during flash floods occurs in large areas of South-East Asia including Bangladesh, resulting in increased mortality of plants as well as low productivity of rice crops. A pot experiment was conducted at the Net House, Department of Crop Botany, Bangladesh Agricultural University, Mymensingh, during Aman season from July 2017 to December 2017 to evaluate morphological and phenological traits associated with submergence tolerance in rice. The experiment consisted of two factors—Rice cultivars (Binadhan-11, Binadhan-12, BRRI dhan51 and BRRI dhan52 as tolerant and BRRI dhan49 as susceptible) and submergence stress for 14 days at vegetative stage and control. Submergence stress was imposed by dipping of pots into a water tank with about 90 cm depth of water. After desubmergence, the plants were grown with proper care till maturity. Control plants are maintained in the pot house of field laboratory. Leaf greenness was measured after desubmergence to physiological maturity. The tolerant cultivars maintain higher leaf greenness for a long time than the susceptible cultivar after desubmergence. Reduction of grain filling rate and yield was significantly higher in susceptible cultivar than the tolerant cultivars. Among the five cultivars, BRRI dhan51 contributed the highest yield under stress treatment. Submergence tolerant rice cultivars (Binadhan-11, Binadhan-12, BRRI Dhan51 and BRRI Dhan52) had maintained higher tiller number, 1000-grain weight and the higher number of grains per panicle during submergence, as compared to susceptible rice cultivar BRRI Dhan49.
 
 J Bangladesh Agril Univ 17(4): 545–550, 2019
Highlights
Rice (Oryza sativa L.) belonging to the family Poaceae and subfamily Oryzoideae is the staple food of the people of Bangladesh
Five cultivars of rice of which one submergence susceptible Bangladesh Rice Research Institute (BRRI) dhan49 and other four submergence tolerant rice cultivars BRRI dhan51, BRRI dhan52, Binadhan-11 and Binadhan-12 were used for the study
The submergence stress had a significant effect on grain yield
Summary
Rice (Oryza sativa L.) belonging to the family Poaceae and subfamily Oryzoideae is the staple food of the people of Bangladesh. It is the second most important cereal crop in the world (FAO, 2017). World rice production in 2017 was 759.6 million tonnes (503.9 million tonnes, milled basis) with an increase of 0.6% from previous year (FAO, 2017). It is a major thirst to develop submergence tolerant rice cultivars to meet the present food demand throughout the world. Submergence subjects plants to the stresses of low light, limited gas diffusion, effusion of soil nutrients, mechanical damage, and increased susceptibility to pests and diseases (Ram et al, 2002). In addition to the O2 deficiency, production of toxic substances such as Fe2+, Mn2+, and H2S by reduction of redox potential causes severe damage to plants under waterlogged conditions (Drew and Lynch, 1980)
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