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Abstract : |
Germination of 15 rice cultivars were investigated on a temperature gradient plate with a range of temperatures 13.7-37.3 أƒâ€ڑأ‚آ°C to identify rice genotypes tolerant of low temperature which would facilitate in cultivar selection for winter sown rice (Boro rice) in Bangladesh. The results demonstrated a plateau of more than 90% final germination between 18 and 33 أƒâ€ڑأ‚آ°C for eleven cultivars. Three cultivars had a plateau of less than 90% germination. At the lowest temperature seven cultivars achieved 80% germination whereas lower quality cultivars showed less than 8% germination. The rest of cultivars were intermediate with about 30-50% germination. The rate of germination (the reciprocal of median germination time) for all cultivars increased linearly from 13.7 up to 30.9 أƒâ€ڑأ‚آ°C and then declined rapidly between 30.9 and 37.3 أƒâ€ڑأ‚آ°C. At optimum temperature cultivars with lower quality seed sample (BR1, KS, KG and BR30) had the lowest rates of germination along with cv. BR5. Rates of germination at higher temperatures (20.1 and 30.9 أƒâ€ڑأ‚آ°C) were significantly related to the rates of germination at lower temperature (13.7 and 15.8 أƒâ€ڑأ‚آ°C). The base temperature differed little between cultivars (range 12.6أƒآ¢أ‚€أ‚“13.9 أƒâ€ڑأ‚آ°C) and optimum temperature ranged from 29.9 to 33.5 أƒâ€ڑأ‚آ°C (mean 32.1 أƒâ€ڑأ‚آ°C). Thermal time to achieve 50% germination at sub-optimal temperatures ranged from 526 to 1667 أƒâ€ڑأ‚آ°C h and differed significantly between cultivars. Cultivars with lower quality seeds and BR5 required than above 900 أƒâ€ڑأ‚آ°C h. The application of these findings to the development of routine methods to identify rice genotypes able to germinate at lower temperature is emphasized. Measurements of rates of germination at higher temperatures (20 and 30 أƒâ€ڑأ‚آ°C) could provide a relatively rapid screening method indicative of low temperature performance for large numbers of genotypes., Germination of 15 rice cultivars were investigated on a temperature gradient plate with a range of temperatures 13.7-37.3̊C to identify rice genotypes tolerant of low temperature which would facilitate in cultivar selection for winter sown rice (Boro rice) in Bangladesh. The results demonstrated a plateau of more than 90% final germination between 18 and 33̊C for eleven cultivars. Three cultivars had a plateau of less than 90% germination. At the lowest temperature seven cultivars achieved 80% germination whereas lower quality cultivars showed less than 8% germination. The rest of cultivars were intermediate with about 30-50% germination. The rate of germination (the reciprocal of median germination time) for all cultivars increased linearly from 13.7 up to 30.9̊C and then declined rapidly between 30.9 and 37.3̊C. At optimum temperature cultivars with lower quality seed sample (BR1, KS, KG and BR30) had the lowest rates of germination along with cv. BR5. Rates of germination at higher temperatures (20.1 and 30.9̊C) were significantly related to the rates of germination at lower temperature (13.7 and 15.8̊C). The base temperature differed little between cultivars (range 12.6–13.9̊C) and optimum temperature ranged from 29.9 to 33.5̊C (mean 32.1̊C). Thermal time to achieve 50% germination at sub-optimal temperatures ranged from 526 to 1667̊C h and differed significantly between cultivars. Cultivars with lower quality seeds and BR5 required than above 900̊C h. The application of these findings to the development of routine methods to identify rice genotypes able to germinate at lower temperature is emphasized. Measurements of rates of germination at higher temperatures (20 and 30̊C) could provide a relatively rapid screening method indicative of low temperature performance for large numbers of genotypes. , |
