Effect of Water Deficit Stress at Various Growth Stages on Yield, Yield Components and Water Use Efficiency of Five Rapeseed (Brassica napus L.) Cultivars

In order to study the effect of water deficit stress at various growth stages on yield, yield components and water use efficiency of rapeseed (Brassica napus L.) cultivars, a field experiment was conducted as split-plot in a randomized complete block design with three replications during 2009-2010 growing seasons in Abarkouh, Iran. Full irrigation based on four different soil water depletion regimes were applied to the main plots including: 40% of available water depletion (AWD) during full growth period (I¬1), 80% of AWD during stem elongation stage to maturity (I2¬), 80% AWD from flowering stage to maturity (I¬3) and 80% AWD from seed filling stage to maturity (I4). Five rapeseed cultivars as sub plot units including: Hayola¬401, Zarfam, Modena, Sarigol and Option¬500 were investigated. Analysis of variance showed that there were significant (P≤0.01) differences among irrigation levels for yield, yield components and water use efficiency.¬ In this study, insufficient soil moisture at the three growth stages, reduced yield components such as seed number per pod and 1000-seed weight by 13.3% and 15.6%, respectively, and led to reduced seed yield as much as 21.4% compared to the control. Reduction of seed yield in each three treatments I¬2, I¬3 and I¬4 was mainly due to reduction in pods and seeds per pod. Water use efficiency decreased more in I2, I3 and I4 treatments than the control. Among the cultivars, Hayola¬401 had the highest water use efficiency. Statistical comparisons showed that Zarfam cultivar produced the highest seed yield (4006 kg ha-1) and Option500 produced the lowest seed yield (2515 kg ha-1).