Effect of Water Deficit¬ Stress at Terminal Growth Stages on Yield and Seed Oil Quality of Rapeseed (Brassica napus L.) Cultivars

In order to study the effect of water deficit stress at different growth stages on yield and seed oil quality of rapeseed cultivars, a field experiment was conducted as split-plot in a randomized complete block design arrangement with three replications in 2009-2010 growing seasons in Abarkouh in Iran. Four levels of irrigation were located in the main plot including, (I1) normal irrigation based on 40 percent accessible water, (I2) irrigation based on 80 percent accessible water from stem elongation stage to maturity, (I3) irrigation based on 80 percent accessible water from flowering stage to maturity, (I4) irrigation based on 80 percent accessible water from seed filling stage to maturity and five rapeseed cultivars including, Hayola 401,Zarfam, Modena, Sarigol and Option 500 were considered as sub plot. The analysis of variance showed that there were significant differences between cultivars and different levels of irrigation for seed yield, oil content, protein content, meal glucosinolate content and fatty acids (P<0.01). In this study, water deficit stress reduced seed yield (I2:¬28%¬, I¬3:26%¬ and I4:10%), oil content (I2:¬5.6%¬, I¬3:6.2%¬ and I4:4.3%)¬, oleic acid¬ (I2:¬1.1%¬, I¬3:0.1%¬ and I4:0.7%) and linolenic acid (I2:¬7.4%¬, I¬3:6.7%¬ and I4:7.5%)¬ and increased protein content (I2:¬0.2%¬, I¬3:1.6%¬ and I4:3%)¬, meal glucosinolate content (I2:¬155%¬, I¬3:109%¬ and I4:171%)¬ and linoleic acid (I2:¬6.3%¬, I¬3:5.4%¬ and I4:5%). Also, cultivar × irrigation effect were significant on meal protein, oleic acid and linolenic acid. The highest meal protein content (50.2%) and linolenic acid (19.4%) was detected in I3 level os Zarfam and the highest oleic acid content (70.7%) was detected for Modena cultivar under control irrigation treatment. The lowest meal glucosinolate content was obtained in Hayola 401 cultivar (19/93 Μmol/g−1). Among the five cultivars, it was shown that Hayola 401 and Zarfam cultivars produced the highest seed yield (3991 and 4006 kg/ha, respectively). Overall, Hayola 401 and Zarfam cultivars were superior due to high seed yield, oil and protein yield. But the superior quality oil (due to low saturated fatty acids (6%)) was detected in Modena and Sarigol cultivars.