In order to determine the effect of vernalization on phenology and development rate of canola varieties, an experiment was conducted at research farm of Gorgan University of Agricultural Science and Natural Resources during 2005-2006. The experiment was a randomized complete block design arranged in split plot with four replications. Six varieties of canola (Option500, RGS003, Hyola308, Hyola60, Hyola420 and Hyola401) were as main-plots, and six vernalization periods (0, 10, 20, 30, 40 and 50 days) were as sub-plots. The results showed that increase in the duration of vernalization from 0 to 50 days, caused decrease in the number of days to development stages (beginning of green and yellow bud, and beginning and end of flowering), and caused increase in development rate. The response of all varieties to vernalization was quantitative, indicating that no-vernalization treatment did not stop their flowering. The varieties could develop to the flowering with 85-94% of their maximum development speed. In Hyola308, the vernalization demand was 30 days, but, in other varieties, that was 50 days. A simple vernalization model was produced according to the result of this study, which could be used in simulation models of canola phenologic development.
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