Determination of Phenological Response of Spring Canola (Brassica napus L.) Genotypes to Sowing Date, Temperature and Photoperiod

Effect of sowing date (SD), temperature and photoperiod on different phenological stages of spring canola (Brassica napus L.) genotypes were evaluated at Agricultural Research Station of Gonbad during 2002–2004 growing seasons. The experimental design was a split plot arrangement in RCBD with four replications. Four sowing dates Nov. 06th, Nov. 21st, Dec. 06th and Dec. 21st were assigned to main plots, and four genotypes Hyola401, S3, Quantum and Option500 were randomized in sub-plots. The number of days from emergence to the commencement of flowering (DEF), and from commencement of flowering to physiological maturity (DFM) decreased significantly with delay in SD. Canola phenology was affected by different weather conditions in two growing seasons. In both seasons, there were strong linear relationships between SD and the number of days from sowing to emergence (DSE), SD and DEF, and SD and DFM. There were negative linear relationships between mean air temperature at different developmental stages and duration of those periods, explaining 86, 89 and 92% of the variation for DSE, DEF and DFM developmental periods, respectively. Therefore, the variation in air temperature in different SD in two growing seasons well determined the duration of DSE and DFM, but the duration of DEF was affected by both temperature and photoperiod during that period. The relationships of SD, temperature and photoperiod with phenology of canola genotypes can be used for developing growth and developmental models.