evaluation of spring rapeseed cultivars response to spring and autumn planting seasons

sowing date is an important determinant of yield in canola. cultivation of winter rapeseed cultivars in semi arid regions of iran however it has high potential for production, but, mentioned cultivars are late maturity and this late maturity cause to that silique formation and seed filling periods mature in the same time with hot and dry weather condition. in contrast, spring rapeseed cultivars are shorter growth duration and in this regard, identification of spring rapeseed cultivars with high cold tolerance for autumn planting cause to early harvest. in order to investigation of spring rapeseed cultivars reaction to spring and autumn planting dates, an experimental was carried out in a split plot design based on rcbd with four replications for two years (2004-2006) in karaj. treatments were included planting season in two levels as main plots such as common planting date, autumn planting (27 september) and spring planting (25 march) and spring rapeseed varieties as sub plots in 24 levels. the results indicated that simple effects of planting season and variety and also interaction effect on silique per plant, seed per silique, 1000 seed weight, seed yield, oil yield, biologic yield and harvest index were significant at 1% level probability. in autumn planting, hyola 401 with greatest 1000 seed weight and high seed per silique had the highest seed yield (4689 kg.ha-1) and hyola 330 produced the maximum oil yield (2165 kg.ha-1), wherease rg 405/03 had the maximum seed yield and oil yield (2066 and 713.6 kg.ha-1, respectively) in spring planting. on the basis of this result, some of spring rapeseed cultivars with high cold tolerance and high potential such as hyola 401 could be planting in early autumn at moderate cold regions of iran like karaj.