Effect of Terminal Drought Stress on Seed Yield and Its Components of Rapeseed Cultivars

BACKGROUND: Drought stress is known as the most important factor limiting the growth and crop production. Therefore, the selection of genotypes that has higher yield stability in good crops can play a significant role and impact in the development of rapeseed cultivation with acceptable economic performance in the country. OBJECTIVES: Current study was carried out to assess effect of terminal drought stress on seed yield and its components of Rapeseed cultivars. METHODS: An experiment was performed as a factorial split plot and in the form of a randomized complete block design with three replications. Irrigation treatment included normal irrigation (irrigation after 80 mm of evaporation from Class A pan) and irrigation cut-off from the pod formation stage onwards in the main plots, planting dates including September 26 and October 26 and four rapeseed cultivars including Tassilo, Elvise, Neptune, and Okapi were evaluated in a factorial form in sub-plots. RESULT: The results revealed that irrigation cut-off and delay in planting date had a significant effect on reducing plant height, number of sub-branches per plant, number of pods per plant, number of grains per pod, and 1000-grain weight. Cultivars were significantly different in terms of all evaluated traits. Elvise and Neptune cultivars had the highest grain yield with (3346) and (3220 kg.ha-1), respectively, under normal irrigation conditions and with a mean of (3211) and (3081 kg.ha-1), respectively, under irrigation cut-off conditions. This advantage was mainly due to an increase in the tank capacity of the yield components. Therefore, Elvise and Neptune cultivars can be introduced with acceptable production stability under normal irrigation conditions and water stress conditions after silique formation. CONCLUSION: Among the studied cultivars of rapeseed, under normal irrigation and cut-off of irrigation conditions on both planting dates of Sep. 26 and Oct.26, Elvise cultivar showed the highest grain yield per unit area of production and good compatibility. The mentioned cultivar can be recommended in the areas similar to the studied area (Karaj), where there is a possibility of water stress in the late stages of growth.