Estimation of Base Temperature for Germination of Rapeseed (Brassica napus) using Different Models
Germination tests of 8 rapeseed varieties (Brassica napus L.) were performed in incubators at constant temperatures of 3, 5, 8, 10, 13, 18 and 23oC. The germination speed of rapeseed declined as temperature decreased from 23 to 3oC. The cold-resistant varieties still maintained higher final germination under low temperature despite the extension of germination process. Five conventional models (Linear regression of percent germination per day, germination rate index, percent germination per day and reciprocal time to median germination versus temperature, and repeated probit analysis) were evaluated to estimate the base temperature for seed germination. The repeated probit analysis model was found the most suitable for estimating the base temperature of rapeseed due to the lowest respective root mean square error, and the mean base temperatures estimated by this model were 1.4 and 4.1oC for the cold-resistant and cold-sensitive varieties, respectively. The repeated probit analysis model was also able to predict the germination percentage at any given time when the base temperature was confirmed. This research provides useful information and has implication for evaluation of different models for the estimation of base temperature for rapeseed germination and the management of rapeseed production with respect to sowing time.