Study of Important Agronomic Traits and Their Relationships under Normal and Drought Stress Conditions in Doubled Haploid Lines of Oilseed Rape

In order to investigate the relationships among yield, yield components and other important agronomic traits in rapeseed under normal and stress conditions, 135 doubled haploid lines derived from the cross between a Korean spring line "Yudal" and a French winter line "Darmor” along with the parents and seven commercial cultivars were evaluated using a simple lattice design with two replications in University of Tehran, in 2009-2010. Measured traits were days to flowering, plant height, height of lowest primary effective branch, length of main inflorescence, seed yield, 1000-seed weight, seed per silique, silique length, silique beak length, silique thickness and silique density. There was a large variation in the population for different traits. Correlation analysis showed that days to flowering and height of lowest primary effective branch had the highest negative and positive correlation with grain yield, respectively. The regression and path analysis showed that days to flowering, height of lowest primary effective branch and plant height as important components having the highest direct effect on grain yield. Reduction of grain yield and 1000-kernel weight were affected mostly by drought stress. Nonetheless some agronomic traits such as pod thickness, pod length and beak length were not significantly changed under drought stress. Doubled haploid lines were grouped using principal components analysis based on drought tolerance indices. The first two principal components explained 98 percent of data variation.