Drought stress affects plant growth and development and ultimately, reduced grain yield of rice. But stress at different growth stages may respond differently which is still unclear. Therefore, a pot experiment was carried out with six rice genotypes to determine the critical growth stage where drought stress effect on yield reduction and to find stress tolerance mechanism in rice genotypes. Drought stress (control i.e. no stress and 40% field capacity, FC) was imposed on Binadhan-13, Kalizira, BRRI dhan34, Ukunimodhu, RM-100-16 and NERICA mutant rice genotypes at maximum tillering, panicle initiation and grain filling stages and discontinued when the specific stage was over. The experiment was laid out in a complete randomized design with three replications. Drought stress affected number of effective tiller hill-1, number of spikelets panicle-1, filled grains hill-1, 1000-grain weight and grain yield. Binadhan-13 produced the highest grain yield and the lowest sterility under drought stress at grain filling stage. Percentage of spikelet sterility increased under drought stress (40% FC) especially at the panicle initiation stage resulting low grain yield. Among the tested genotypes Binadhan-13 performed well by reducing spikelet sterility under drought stress condition. For 1000-grain weight and grain yield, grain filling stage was found more crucial. From the current research, drought tolerance mechanism was found in genotypes Binadhan-13 and NERICA mutant.
Key words: Crop phenology, Water deficits, Rice productivity, Photosensitive rice cultivars
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