Botany Research International 2 (4): 295-303, 2009 ISSN 2221-3635 © IDOSI Publications, 2009 Corresponding Author: Mirza Hasanuzzaman, Department of Agronomy, Faculty of Agriculture, Sher-e-Bangla Agricultural University, Sher-e-Bangla Nagar, Dhaka-1207, Bangladesh 295 Screening of Indica Rice (Oryza sativa L.) Genotypes Against Low Temperature Stress Kamrun Nahar, J.K. Biswas, A.M.M. Shamsuzzaman, Mirza Hasanuzzaman and H.N. Barman 1 2 1 3 2 Department of Agricultural Botany, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh 1 Plant Physiology Division, Bangladesh Rice Research Institute, Gazipur, Bangladesh 2 Department of Agronomy, Sher-e-Bangla Agricultural University, Dhaka-1207, Bangladesh 3 Abstract: In this investigation, genotypes having yield level more than 400 g m were selected primarily as low 2 temperature tolerant. There were short and long duration genotypes in those groups. The combination of yield components was quite better in Group I. The genotypes having the highest spikelet number with better yield was found in Group III and IV but they had lower thousand-grain weight. The maximum and minimum temperature around panicle initiation (PI) were 28.7°C and 10.9°C for short duration genotypes and 24.4 and 11.0°C for long duration genotypes. The genotypes encountered low temperature and low solar radiation from vegetative to reproductive phases. A few genotypes maintained better phenotypic acceptability. Most of the selected genotypes experienced spikelet degeneration symptom. The genotypes (Group I, III and IV) producing huge number of spikelets might able to execute panicle differentiation at the initiation of panicle development. But at the subsequent stage there must have some growth impairment activities. In contrast, the genotypes (Group II and V) which having lower number of spikelet m might be affected primarily at the differentiation 2 stage then at the reduction division stage. The genotypes having short growth duration might have the tolerance to withstand low minimum temperature and those with long growth duration are appeared to have stress avoidance mechanism. As D between the cluster 2 and cluster 3 was the highest, breeders could have 2 the better chance of heterosis crossing between these two groups. Key words: Screening Oryza sativa Cold stress Phenotypic acceptability Yield Tolerance INTRODUCTION the reproductive phase. Many authors studied the causes The rice plant could normally grow between 20°C and depends on the development stage and length of the 35°C and these critical temperatures vary with genotype, exposure of the panicle to low temperature [4,5]. On the duration of critical temperature, diurnal changes and other hand low temperature may also result in physiological status of the plant [1]. Rice might suffer non-receptive stigma, fertilization failure of post from low temperature at the reproductive stage of the fertilization development. These important aspects of cropadd reference here [1]. Even low temperature at the flowering behavior in rice were studied by Nizigiyimana crop establishment and tiller development stage [6] who also reported that low temperature sterility due to (vegetative phase) of the crop might affect the growth and degeneration of embryo sac, malformation of ovaries and development of the crop. The most sensitive stages deformation of young sporocytes during meiosis. against the stresses are agronomic panicle initiation In Bangladesh, the low temperature prevails from stages (24 days before heading), reduction division stage October to early March. The temperature often reaches (12-14 days before heading) and anthesis (0 days before below 20°C. Boro (winter rice), one of the most important heading) stage [2,3]. rice crops, might suffer from critical low temperature at the There are various types of damages due to low different growth stages from germination to maturity. temperature. The vegetative phase-stress may be The growing season of boro is longer, extending from recoverable but make the crop experience flash flood November to June. Bangladesh Rice Research Institute submergence by extending the growth duration. But the (BRRI) recommends seeding of short and long duration unrepairable loss is occurred if the stress is imposed at varieties between 15 and 30 November and 5 and 25 of sterility [2-4] Sterility caused by low temperature