Evaluation of drought stress effect at terminal growth stage on quantitative and qualitative yield of rapeseed (Brassica napus L.) cultivars

To evaluate the drought stress effect at terminal growth stage on yield of 12 rapeseed cultivars, an experiment was conducted with split-plot arrangement based on randomized complete block design with four replications at experimental field of Seed and Plant Improvement Institute, Karaj-Iran during 2005-06. Irrigation at two levels (irrigation after 80 mm evaporation from class A pan, as control and withholding irrigation from silique formation until crop maturing time, as stress conditins allowcated to main plots and twelve rapeseed cultivars were used in sub plots. The number of silique in main stem, number of silique in lateral branches, silique fertility ratio and grain yield were low in drought stress conditions (p< 0.05). There were significant variations in all studied traits between evaluated cultivars. Grain yield in drought stress treatment was decreased (30%), when silique abortion was occurred due to water stress. In full irrigation treatment (control), the grain yield of Orient cultivar (2817 kg.ha-1) and at drought conditions, the grain yield of Opera cultivar (2058 kg.ha-1) were the highest amounts. The lowest oil percentage (39.8) and the highest protein percentage (23.3) were for Talaye cultivar, while the highest oil percentage (42.6) was for Option500 cultivar.