INVESTIGATION OF COLD SURVIVAL MECHANISM OF DIFFERENT RICE CULTIVARS AT SEEDLING STAGE BASED ON BIOCHEMICAL AND PHYSIOLOGICAL CHARACTERISTICS

Abstract

A study was conducted to screen out the low temperature tolerate boro rice seedlings during the period of November, 2011 to January, 2012 for facing upcoming rice production challenge in northwest Bangladesh. The experimental period was characterized by prevailing low environmental temperature of below 15°C. Seven rice cultivars (V1: Poshu sail; V2: BRRI dhan28; V3: Jirashail; V4: Nerica-4; V5: GSR-IRRI 1; V6: Purple rice; V7: BRRI dhan50/ Banglamoti) both from local and HYV varieties were selected for the research. The amount of proline, chlorophyll-a, chlorophyll-b, chlorophyll-a/b ratio, total carotenoid and total chlorophyll content was markedly influenced by low temperature and found to increase its content in rice seedling with exposure to low temperature. The V6 (purple rice) rice cultivar synthesized the highest proline (1.06 mg g”) followed by V4 (NERICA-4) which contained 0.87 mg g” proline. The highest amount of chlorophyll-a (7.071 mg g”'), chlorophyll-b (3.335 mg g’') and total chlorophyll (10.52 mg g”) was measured in V4 (NERICA-4). The V3 (Jirashail) rice cultivar was found to synthesize highest amount of total carotenoid (1.247 mg g’). The highest chlorophyll-a/b ratio (2.887) was also observed in V3 (Jirashail). The highest leaf relative water content (94.42% at 32 DAS) was found in V2 (BRRI dhan 28). The highest shoot length was measured in V1 (100.30 mm at 36 DAS) and the highest percent shoot dry weight was found in V3 (31.01% at 12 DAS) followed by V4 (28.34% at 12 DAS). Again, the highest percent root dry weight (72.96% at 12 DAS) was found in V3 (Jirashail). The highest amount of protein (13.99%) and starch (28.84%) content was found in V4 (NERICA-4) at 36 DAS. The highest percent of seed germination was also found in V4 (85%) at 10 DAG. In this study, the V4 (NERICA-4) and V3 (Jirashail) cultivars (among the HYV and local cultivars) showed comparatively better potentiality to survive at low temperature (below 15°C) prevailing areas during boro season by synthesizing elevated amount of proline.