SCREENING OF RICE GENOTYPES AGAJNST LOW TEMPERATLIRE STRESS

Abstract

The research work was conducted at the Bangladesh Rice Research Institute. Gazipur from October 2007 to May 2008 with 244 rice breeding lines obtained from different sources. The seeds were sown on IS October 2007 so that the genotypes would have the experience of low temperature stress at their vegetative as well as reproductive phases. Cluster and Discriminant Function Analysis was perlornied to screen out genotypes having better performance with respect to phenotype as well as yield perk)nnance. Accordingly, genotypes 177496-31-2-1-3. 1R77504-36-3-3- I. BR7528-2R-20-1. 11173689-19-I. 1R62266-42-6-2 and PSBRC68 were selected from cluster I. Genotype 8(1358-I was selected from cluster 3. Another genotype RC1358-3 was selected from the cluster 4 lbr desirable attributes. Geuol\ pes having yield level more than 400 g ni' were selected primarily as low temperature tolerant. There were short and long duration genotypes in those groups. Spikcict ni'2 played the most important role in grouping the genotypes. The combination of yield components was quite better in Group I. The genotypes having the highest spikelet number with better yield was iotLnd in Group Ill and IV but they had lower thousand-grain weight. The maximum and mimmttm temperature around panicle initiation (Pt) were 28.7 "C and 10.9°C for short duration genotypes and 24.4 and 11.0°C (hr long duration genotypes. Solar radiations during those periods were 235.2 and 191.5 Cal cm'2. tue critical low temperatures for agronomie P1 (24 (lays to flowering) and reduction division are 18 and I 9SC. respectively. In reality, the occurrence of low temperature was fur below than those of the critical marks. The genotypes encountered low temperature and low solar radiation from vegetative to reproductive phases. A few genotypes li&e 11(77496-3 l-2-t-3-1 (Group 1) and 1R77496-31-2-1-3-2 (Group 11) maintained better phenotvpic acceptability. Most of the selected genotypes experienced spikelet -  degeneration symptom. The genotypes (Group 1. 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 ol spikelet rn'2 might be aifeeted primarily at the diliërentiation stage then at the reduction division stage. The varieties which were able to maintain their good phenotype were tolerant to low temperature stress. Sonic of the genotypes having an exciting level of yield indicated their all-round tolerance to the cold. It may be concluded that some of the genotypes could be selected as high yielding and better performing genotypes from group I. Ill and IV. The genotypes selected from this study have significant tolerance to critical low temperature. 'I he 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 1)2 between the cluster 2 and cluster 3 was the hiuhest. A  breeders could have the better chance of heterosis crossing between these two groups. CONTENTS Chapter T