Document Type : Research Paper



In order to evaluate the effects of delayed sowing date on quantitative and qualitative traits of three winter rapeseed (Brassica napus L.) cultivars, two split plot field experiments, arranged in complete block designs with three replications, were carried out in Agricultural and Natural Resources Research Center of Markazi Province, Arak (Iran), during 2006-2008 growing seasons. Three rapeseed cultivars (Okapi, Modena and Licord) and three sowing dates (October 2, 12 and 22) were randomized in main plots and sub-plots respectively. The lowest grain yield (1723 kg/ha), 1000-seed weight (3.34 g), seed number per pod (22.01), pod number per plant (70.34), plant height (110.8 cm), second branch number per plant (2.92), days to end flowering (244.79), length of maturity (29.22), seed oil content (45.5%), oil yield (806 kg/ha), seed protein percentage (15.54), harvest index (24.94%), biological yield (6673 kg/ha), grain yield per plant (2.99 g) and dry matter remobilization (64 mg/plant) were obtained on third sowing date. The interaction effect between year and cultivar was significant for traits such as grain yield, 1000-seed weight (P<0.05) and pod number per plant (P<0.01). Also the interaction effect between year and sowing date for grain yield, seed number per pod and pod number per plant was significant at 1% probability level. The interaction effect between cultivar and sowing date was significant for 1000-seed weight (P<0.05), pod number per plant, seed protein percentage and harvest index (P<0.01). In addition, interaction effect between year, cultivar and sowing date was significant for grain yield and plant height at 1% probability level. Thus, it can be concluded that annual variability in the growth environment is responsible for the most of large year to year yield differences. There was positive and significant correlation between grain yield and the most traits such as 1000-seed weight, seed number per pod, pod number per plant, plant height, second branch number per plant, days to maturity, length of maturity, seed oil content (%), oil yield, seed protein percentage, harvest index, biological yield, grain yield per plant and dry matter remobilization except days to initial flowering and days to end of flowering but correlation coefficient between grain yield and length of flowering was negative but significant. In this research Licord cultivar had more grain yield than other cultivars that could be due to genetic diversity among cultivars for using growth sources in direction of grain yield enhancement per unit area.