Quantification of the rapeseed cultivars germination using hydrothermal time model

The objective of this study was to predict the hydrothermal time parameters of five rapeseed cultivars germination using Bradford’s approach. The experiment was a completely randomized in a factorial arrangement of treatments with three replications. The factors were temperature at 6 levels (5, 10, 15, 20, 25 and 30°C) and 5 levels of water potentials (0, -0.3, -0.6, -0.9 and -1.2 Mpa). Application of this model had the highest performance in germination predicting of two cultivars RGS003 and Hayola 4815 with 0.904 and 0.900 coefficients of determinations and the 0.084 and 0.081 mean squared errors, of  respectively. Base temperature was 2.37°C for Hyola401 and in other cultivars was 0°C. Optimum temperature was variable from 23.36°C in Zabol10 to 29.76°C in Hyola401. The mean base water potential varied from -0.3 in Zabol10 to -0.134 MPa in Hyola4815 between cultivars. The Bradford model fit well with data from different rapeseed cultivars. Model prediction of germination indices indicated Fitting of the model showed that indicators such as temperature-humidity coefficient in the population followed the normal distribution. While a large percentage of the population is around the average, large variances in cardinal temperatures and hydrotime parameters within cultivars necessitate further reaserches to improve the germination uniformity of rapeseed cultivars.