Restricted Irrigation Regimes and Rapeseed High-Yielding Genotypes Can Be Applied to Cope With the Water Shortage Crisis and More Stable Oil Production

To investigate the quantitative and qualitative yields of different rapeseed genotypes under optimal water supply and restricted irrigation regimes, a split plot experiment was arranged in a randomized complete blocks design with three replicates in the 2018–19 and 2019–20 growing seasons. The Main plots included irrigation regimes at three levels of optimal water supply regime, withholding irrigation from the beginning of flowering, and withholding irrigation from the beginning of silique setting. The sub-plots contained 11 Iranian rapeseed genotypes (Dalgan, Zafar, Sarigol, RGS003, Hyola4815, Hyola401, Zabol10, Jerom, Jerry, Julius, and Jacomo). The highest rapeseed seed yield (3463 kg ha⁻¹), oil content (43.09%), and oil yield (1492 kg ha⁻¹) were obtained from the optimal water supply regime. Drought stress (restricted irrigation from silique setting and flowering stages) decreased seed yield (28 and 49%), oil content (4 and 7%), and oil yield (31 and 52%). Fatty acids compositions of rapeseed genotypes differently responded to drought stress conditions. Restricted irrigation regimes enhanced the linolenic acid, erucic acid, and glucosinolate contents, while the palmitic acid, oleic acid, and linoleic acid content were reduced when the rapeseed plants were subjected to drought stress. Overall, our findings suggest that the Sarigol genotype due to acceptable seed and oil yield as well as high-quality oil under three studied irrigation regimes can be recommended for cultivation in arid and semi-arid regions like Iran.