To investigate the effect of sowing date on yield and qualitative traits of canola cultivars and cope ‎with late-season drought stress, an experiment was carried out for two planting years in Karaj (Iran). ‎Sowing dates in six levels including three fall and three winter sowing dates were considered as the ‎main factor and five canola cultivars (RGS003, Dalgan, Zabol10, Hyola401 and Hyola4815) as the ‎sub-factors. The results showed that except for palmitic acid, the simple effect of sowing date on all ‎the studied traits was significant in winter. The simple effect of cultivar on all traits in fall was ‎significant and in winter, it was only significant on the seed yield and seed oil yield. The interaction ‎between sowing date and cultivar in fall is the reason of significant effect of seed oil yield, linoleic ‎acid, linolenic acid, erucic acid and glucosinolate and in winter, it is the reason for the significance of ‎seed yield, oil content, oil yield and erucic acid. Dalgan cultivar had the highest seed yield and oil ‎yield on sowing date of October 7, and had the highest levels of oleic, linoleic and palmitic fatty ‎acids. In addition, with low and standard erucic acid and glucosinolate, this cultivar is recommended ‎based on the results of this study.‎ تفاصيل المقالة

Water shortage or drought stress is an environmental factor that strongly affects crops ‎productivity in various regions of the world. Sowing date as a factor affecting the growth ‎and yield of oilseed crops can alleviate drought stress occurring in reproductive stage. To ‎assess this, agronomic and physiological response of five canola genotypes (L1030, L1204, ‎L1110, L1114 and Okapi) to drought stress were evaluated at two early and late sowing ‎dates (7th and 27th October, respectively) as a two-year field experiment. Results showed ‎that drought stress significantly reduced the seed yield and yield components of all ‎genotypes at both sowing dates, which was a consequence of damage to photosynthetic ‎pigments, reduction of relative water content. However, early sowing was able to alleviate ‎drought stress effect; as seed yield of different genotypes at early sowing were 38-47% ‎higher than late sowing. Moreover, the measured oil content was not influenced by drought ‎stress and sowing date, so the highest oil content at both sowing dates were recorded in ‎L1204 genotypes. Finally, the results showed that sowing of suitable genotype in the proper ‎date could be an appropriate approach to canola sowing in semi-arid areas.‎ تفاصيل المقالة