RESPONSE OF RICE (Oryza sativa L.) GENOTYPES UNDER VARYING SUBMERGENCE DURATIONS

Abstract

Three pot culture experiments were carried out in the field at Sher-e-Bangla Agricultural University, Dhaka, Bangladesh during aman seasons of 2012 - 2014 to study the response of different rice genotypes under varying submergence durations and to identify the morphological, physiological and anatomical characters those contribute to submergence tolerance and to study the variations among the selected rice genotypes. The experiments were conducted with three tolerant (BRRI dhan52, IR64Sub1, FR13A) and one susceptible genotype (BR5) with four submergence treatments (0, 7, 14, and 21 days of submergence). All experiments were laid out in two factors RCBD with four replications. Different morphological and physiological processes were hampered due to submergence and there existed genotypic variations also. The lower stem elongation and less affected root dry matter help plants to survive under submergence condition. After desubmergence, tiller number, stomatal conductance, net assimilation rate, relative growth rate and absolute grain growth rate were less affected which helped BRRI dhan52 and FR13A to perform better. Different yield components such as number of panicles per plant, number of filled grain per plant, filled grain weight per plant and 100-grain weight were also less affected in BRRI dhan52 and FR13A compared to other two genotypes (IR64Sub1 and BR5). The results indicated that 7DS treatment in BRRI dhan52 produced more or less similar (99%) yield as compared to control which was followed by FR13A(81% of the control). Decreased grain yield per plant under submergence treatment was observed due to reduction in tiller number rather than grain weight per panicle. Larger aerenchyma formation, stronger arrangement of parenchyma, lower membrane leakage, higher proline content, higher stem carbohydrate and lower chlorophyll depletion in BRRI dhan52 and FR13A provided better adaptation capabilities of these genotypes under submergence condition. But in BR5, though the proline content was higher just after desubmergence, the injury label was much higher in this genotype and cells lost their normal physiological functions. Lower chlorophyll a/b ratio in BRRI dhan52 and FR13A indicated that chlorophyll a content was more affected and chlorophyll b content was less affected due to submergence. The genotype BRRI dhan52 showed more submergence tolerance compared to the other genotypes.