Effect of Irrigation Cut-off on Quality Characteristics and Grain Yield of Rapeseed Genotypes under Zinc Application Conditions

This study was conducted to evaluate some qualitative traits (fatty acids, canopy temperature and stomatal resistance) of new rapeseed genotypes in response to irrigation cut-off and zinc application in Karaj. 

This experiment was performed as a factorial split-plot in a randomized complete block design with three replications for two cropping years (2014-2015 and 2015-2016) in Karaj. In this study, irrigation at three levels including normal or controlled irrigation, cessation of irrigation from flowering stage onwards and cessation of irrigation from pod stage onwards, zinc in two levels including normal water (no zinc application), and foliar application with zinc 30 g.L-1 zinc and rapeseed cultivars including Danob, HW113, KR2, L155, HL2012 were placed in sub-plots. 

The results of analysis of variance showed that the interaction effect of irrigation × genotype on 1000-seed weight, seed yield, seed oil percentage, stomata resistance, linoleic acid, linoleic acid, erotic acid was significant at the level of one percent. Also, the interaction effect of irrigation × on × genotype on grain yield, oleic acid, and linoleic acid at 1% level and canopy temperature, palmitic acid, and linoleic acid at 5% level were significant. Zinc reduced the adverse effects of dehydration stress on the tested genotypes so that under normal zinc application and irrigation conditions, L155 genotype with 6310 kg/ha grain yield and the highest percentage of oleic acid (67.3%). Besides, in terms of zinc application and irrigation interruption from the plowing stage onwards, HL2012 and L155 genotypes with grain yield of 5032 and 4826 kg.ha-1, respectively, and the highest percentage of oleic acid (65.8% and 65.7%, respectively) produced. Also, in case of cessation of irrigation from flowering stage onwards, HL2012 and L155 genotypes with 3679 and 3606 kg.ha-1 grain yield, respectively, had the highest percentage of oleic acid (64.3% and 64.2%, respectively). 

In general, the positive effect of zinc application on traits such as seed oil percentage (0.9 %) increased with increasing drought stress intensity and L155 genotype for all water conditions and HL2012 genotype for end-of-season drought stress conditions are recommended for planting in cold temperate regions with a semi-arid climate.