Effect of moisture regimes in different growth stages on seed yield and yield components of rapeseed cultivars (Brassica napus L.)

In order to evaluate the response of rapeseed cultivars to moisture regimes and correlation analysis in different growth stages, an experiment was conducted in 2006-2007 at Seed and Plant Improvement Institute of Karaj, Iran. The experimental design was split plot on basis of randomized block design with 3 replications. Four irrigation levels consisted of irrigation after 80 mm evaporation from class “A” pan as control, stopping the irrigation in stem elongation stage, stopping the irrigation in flowering stage and stopping the irrigation in podding stage were applied in main plots, and subplots consisted of split application of cultivars at four levels (Opera, Modena, Zarfam and Okapi). Results showed that number of pod per plant, pod length, 1000-seed weight, oil seed content and branch number per plant were reduced significantly in response to water deficit stress. Seed yield decreased more than biological yield and resulted in decrease of harvest index. Correlation coefficient analysis revealed that harvest index (r=0.72**), 1000-seed weight (r=0.29*), biological yield (r=0.38**) and oil seed content (r=0.3*) had positive and significant correlation with seed yield. Flowering and podding are most sensitive stages to water stress. Stopping the irrigation from flowering stage also had undesirable effect on grain yield and its components. Among cultivars, Opera produced more seed yield (4053 kg/ha) than the others in normal irrigation and under water deficit stress conditions, Zarfam had maximum seed yield in stem elongation (3569 kg/ha), flowering (2135 kg/ha) and podding stages (2476 kg/ha). Based on the results of this research it can be concluded that Zarfam had better capability to tolerate drought stress and could produce greater seed yield in stress conditions.