INVESTIGATION OF LOW TEMPERATURE EFFECT ON BORO RICE SEEDLINGS FOR SCREENING IN NORTHWEST BANGLADESH

Abstract

A study was conducted to screen out the low temperature tolerant Boro rice seedlings during the period of December, 2014 to January, 2015, Hajee Mohammad Danesh Science and Technology University, Dinajpur. The experiment time was characterized by prevailing low environmental temperature of below 15oC. Eight rice cultivars (V1: Pariza; V2: BRRIdhan29; V3: Shaita boro; V4: BRRIdhan28; V5: Jotapari; V6: BR-16; V7: Pashushail; V8: Hybrid dhan SL-8H) from both local, and HYV origin were selected for the study. Two temperature regime was applied for seedling culture. Ambient temperature (T0) was for field investigation and 4 oC temperature (T1) environment was maintained only for physiological parameters. The changes of leaf proline, chlorophyll content, seedling shoot length, shoot weight, root length and root weight were investigated. The V8 (Hybrid dhan SL.-8H) and V2 (BRRIdhan29) seedling synthesized the higher leaf proline at low temperature than those of other tested cultivars. The highest amount of chlorophyll-a, was in V8T0 seedlings (10.03 mg g -1 ), while chlorophyll-b (2.063 mg g -1 ) and total carotenoid (4.0470 mg g -1 ) were the highest in V3T0. The highest chlorophyll-a/b ratio (6.729 mg) was observed in V7T0. The highest shoot length was measured in V1 (10.11 mm at 30 DAS) and the highest shoot dry weight was found in V8 (84.03 mg at 30 DAS). Again, the highest root length (5.713 mm) and root dry weight (44.83 mg) was measured in V8 at 30 DAS. In this study, the V8 cultivars (among the HYV and local cultivars) showed comparatively better potentiality to survive at low temperature (below 15oC) by over synthesizing proline, chlorophyll-a, chlorophyll-b and higher partitioning dry biomass in root and shoot. The study inferred that HYV, V8 (Hybrid dhan SL-8H) might be selected for cultivating as boro rice in the low temperature environment in Northwest Bangladesh.