ORIGINAL ARTICLE

Effects of Low temperature at various growth stages and yield of different rice (Oryza sativa L.) genotypes

The experiment was conducted with two IRRI lines and two BRRI varieties at the research field of Plant Physiology Division of Bangladesh Rice Research Institute (BRRI), Gazipur during October 2010 to September 2011 in Boro season to study the low temperature as cold tolerance effect on rice at vegetative and reproductive stages. All the genotypes (IR77496-31-2-1-3-1, IR62266-42-6-2, BRRI dhan28 and BRRI dhan36) of transplanting date 30 November, 15 December and 30 December showed higher yield except 15 November transplanted rice. The 15-November transplanted rice appeared with a significant cold in the reproductive stage. Moreover, BRRI dhan28 was not found to observe as tolerant to low temperature in reproductive stage, and produced the lowest yield 0.71 t/ha and highest (39.47%) sterility. BRRI dhan36 resulted yield 2.18 t/ha and exerted its ability to withstand the jolt of cold to some extent at the reproductive phase and IR62266-42-6-2 pronounced significantly better performance compared to BRRI dhan36. The IR77496-31-2-1-3-1 genotype exhibited the highest yield (4.27 t/ha) and marked as tolerant to cold temperature. All the genotypes performed the highest sterility percentages on 15-November transplanted rice except the genotype of IR77496-31-2-1-3-1 with lower sterility. Vegetative and reproductive stages were encountered at cold temperature in the month of January, 2011. The panicle initiation stage was fallen with (13.1 °C) low temperature and maximum temperature (25.6 °C) in 2nd week of February, 2011 during grain formation stage. Number of grains was naturally degenerated in growth stages where reduction division stage or pollen formation was happened in booting stage. Earliest transplanted date (15 November) revealed the shortest plant height and panicle length at low temperature. Duration of PI, growth and maturity stages were decreased with the advancement of transplanting dates of 30 November, 15 December and 30 December.