Stability of Grain and Oil Yields and Its Components in Oilseed Rape (Brassica napus L.) Under Early and Late Season Drought

Abstract
Evaluation of drought effects on seed and oil yields, its components and selecting water deficit tolerant oilseed rape genotypes were the main goals of this study. The experiment was conducted as factorial based on a randomized complete blocks design with three replications in East Azarbaijan Research Center for Agriculture and Natural Resources during 2010-2011 and 2012-2013. The experimental factors were irrigation with three levels including: non-stressed and drought stress during rosette and seed filling stages (irrigation at 30-35% and 70-75 % available soil water depletion for non-stressed and stressed treatments, respectively) and genotype including six genotypes: Karaj 1, Karaj 3, Opera, Okapi, Licord and Modena. The effect of drought stress on crown diameter and plant dry weight at the time of reaching mean air temperature below oilseed rape base temperature( 5°C), plant height, pods per plant, 1000 seed weight, seed and oil yields, were significant. Occurring water deficit at rosset stage led to significant decrease in crown diameter and plant dry weight. The existence of significant and positive correlations among plant height with the number of pods per plant, 1000 seed weight, seed and oil yields showed the importance of plant height in support of yield.Water deficit during seed filing stage significantly decreased pods per plant, 1000 seed weight and finally seed and oil yields. Among studied genotypes under drought and normal conditions, Okapi and Licord indicated higher seed and oil yields.