PERFORMANCE OF DIFFERENT AUS RICE GENOTYPES UNDER WATER DEFICIT CONDITIONS

Abstract

ABSTRACT Water deficit encountered by rice plant is a common feature in Bangladesh especially in dry season for which rice is grown by supplying irrigation water. Aus rice is a dry season crop dependent on rain or irrigation. In Bangladesh, the Aus rice faces drought problem at vegetative stage. So, it is necessary to develop or introduce drought tolerant high yielding Aus rice varieties. Different rice research institutes like BRRI, BINA have released some drought tolerant rice varieties. Further improvement of those and other rice varieties are required in order to meet up the future rice demand. Considering the above statements four pot experiments were carried out during September 2012 to July 2014 at Agricultural Botany field of Sher-eBangla

Agricultural University, Dhaka. Plants were grown in the rain protected polyethylene shelter to avoid rain under natural light conditions. The first experiment was conducted with eleven BRRI rice varieties (BR21, BR24, BRRI dhan42, BRRI dhan43, BRRI dhan48, BRRI dhan55) and other lines BR6976-11-1, OM1490, BR6976-2B-15 along with the tolerant check varieties Hashikalmi and Dharial. These rice varieties were used to find out their response of roots to water deficit in the soil of root elongation tubes. Due to water stress shoot height decreased and root length increased. And other three experiments were conducted with four drought treatments such as 0 days (control), 7, 10 and 15 days and drought imposed in different age of the plants in the earthen pots. The morpho-physiological and biochemical changes reduced plant growth rate due to water deficit affecting decline in leaf area, specific leaf area, shoot dry weight, panicle dry weight, panicle number, panicle length, number of effective tillers, total dry matter content, stomatal conductance, proline content and grain yield etc. After anthesis, the SPAD value gradually decreased towards maturity. Among the genotypes, BRRI dhan55 produced the highest number of tillers and grain yield per plant. It revealed that Hashikalmi showed significantly taller plant throughout the growing period and developed more tillers. The sensitive genotypes showed reduction in leaf area, number of leaf, dry matter, tiller number and took much longer time to recover and develop new organs. The grain sterility percentage was much higher in BR6976-2B-15 due to water stress treatment compared to other genotypes. The grain yield per plant recorded was the highest at control treatment and gradually decreased with the increasing water deficit duration in all the genotypes. But the grain yield was less affected in BRRI dhan55 and Hashikalmi due to water deficit treatment. Anthocyanin, and proline were increased, sugar and starch were decreased under water deficit conditions. Leaf accumulates anthocyanins under drought conditions and the red colour increased as the intensity of water deficit was increased. Under water stress condition RWC was significantly reduced. RWC declined with the increase of water deficit condition. Stomatal conductance was higher at early drought condition (1 st to 3 rd drought stress) and gradually decreased towards maturity at late water deficit condition (4 th to 6 th drought stress) in all the genotypes. Stomatal conductance was higher in BRRI dhan55 and Hashikallmi and lower in BR 6976-2B-15. The tolerant genotypes BRRI dhan55 and Hashikalmi were less affected under water deficit treatment compared to susceptible genotypes. Among the genotypes, BRRI dhan55 and Hashikalmi were tolerant and BR6976-2B-15, BR6976-11-1 was sensitive or susceptible to water stress considering the different parameters.