The Physiological Response of Rapeseed (Brassica napus L.) Genotypes to Drought Stress

Drought stress is one of the most impactive factors of severe modification in plant physiology eventually leading to a reduction in crop productivity. A split plot-factorial experiment was conducted at the Agricultural Sciences and Natural Resources University of Khuzestan in the 2021-2022 growing season to investigate the effects of irrigation interruption and plant density on spring rapeseed genotypes. The experiment was set up in a randomized complete block design with three replications. The experimental treatments included three levels of irrigation as main plot: (I) (1. Control: no interruption of irrigation, 2. Interruption of irrigation at the beginning of flowering (phenology code 60) until the formation of 50% of the pods (phenology code 75) and 3. Interruption of irrigation at the stage of panicle formation (phenology code 99) until the stage harvest (phenology code 99)) and three levels of plant density (D) (80, 110 and 140 plants per square meter) and canola genotypes (G) (Hayola 4815 and Aram) were arranged in subplots. The study evaluated various sensitivity and tolerance indices to stress, and results showed that the triple interaction effect of IDG on cell membrane stability, photosynthetic pigments, grain protein content, grain yield, and canopy temperature was significant. Significant interaction effects were also observed between IG on grain oil content, DG, and I×D on relative water content leaf (LRWC). The genotype that demonstrated superior tolerance to drought stress had higher values for indices such as STI, YI, MP, GMP, and HM. In general, the highest grain yield was observed in control treatment and density of 110 plants M2 and genotype of Hayola4815 (1572.6 kg. ha-1) and the lowest was observed from interruption of irrigation at the stage of pods formation until harvest and plant density of 140 plants per M2 and Aram genotype (661.87 kg. ha -1).