Pakistan Journal of Biological Sciences1028-88801812-5735Asian Network for Scientific Information10.3923/pjbs.2003.1070.1076Oryza sativa L.) Cultivars]]>AliM. G.NaylorR.E. L.MatthewsS. 122003612Germination of 15 rice cultivars were investigated on a temperature gradient plate with
a range of temperatures 13.7-37.3 °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 °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 °C and then declined rapidly between 30.9 and 37.3 °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 °C) were significantly related to the rates of germination at lower temperature
(13.7 and 15.8 °C). The base temperature differed little between cultivars (range
12.6–13.9 °C) and optimum temperature ranged from 29.9 to 33.5 °C (mean 32.1 °C).
Thermal time to achieve 50% germination at sub-optimal temperatures ranged from 526
to 1667 °C h and differed significantly between cultivars. Cultivars with lower quality
seeds and BR5 required than above 900 °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 °C) could provide a relatively rapid screening method indicative of low
temperature performance for large numbers of genotypes.]]>Adair, C.R.,19688264265Ali, Z.I., V. Mahalakshmi, M. Singh, G. Ortiz-Ferrara and J.M. Peacock,1994Triticum aestivum) genotypes.]]>125367375Anonymous,1999Chaudhary, T.N. and B.P. Ghildyal,197019165168Covell, S., R.H. Ellis, E.H. Roberts and R.J. Summerfield,198637705715De-Datta, S.K.,1981De Datta, S.K.,198622417426Dunbabin, T., J. Learmonth, R.E.L. Naylor and C.E. Mullins,1994Sorghum bicolor under a constant temperature regime.]]>39179184Ellis, R.H., G. Simon and S. Covell,19833810331044Hall, V.L.,1966694042Kamaha, C. and J.D. Maguire,199220181185Kaneda, C. and H.M. Beachell,199461732Kasalu, H., S.C. Mason and G. Ejecta,199370368371Krishnasamy, V. and D.V. Seshu,198929904908Lafond, G.P. and R.J. Baker,198626563567Naylor, R.E.L.,1993123379390Ong, C.K. and J.L. Monteith,198511141160Scott, S.J., R.A. Jones and W.A. William,19842411921199Squire, G.R.,1990Pages: 236Pages: 236Tanida, M.,1996462327Yoshida, S.,1981Pages: 269Pages: 269