Growth and Physiological Characterization in Five Genotypes of Brassica napus Callus Culture under Drought–Induced Osmotic Stress

As the demand for edible oil continues to soar, rapeseed cultivation remains pivotal for sustainable and efficient oil production, catering to the nutritional needs of a burgeoning population. Given the substantial impact of environmental stress on plant productivity, this study aimed to explore the in vitro responses of calli-derived hypocotyls from five Brassica napus genotypes under varying concentrations of polyethylene glycol (PEG) 6000 (0%, 10%, 20%, 30%, and 40%). The objective was to assess various growth and physiological parameters, including Callus Growth Rate (CGR), Relative Water Content (RWC), Index of Tolerance (INTOL), Relative Growth Rate (RGR), and Proline Content (PC). Results unveiled a significant surge in proline content with increasing levels of PEG, with the highest accumulation observed at 40% PEG concentration. These findings suggest that heightened osmotic stress induced by PEG led to a notable rise in proline accumulation in calli-derived hypocotyls. Furthermore, elevated levels of PEG-induced osmotic stress adversely impacted growth parameters such as RWC, RGR, and CGR. Notably, genotypes Geronimo and Arc5 exhibited enhanced drought resistance in in vitro environments compared to other genotypes. These particular genotypes showcased greater resilience and adaptability to PEG-induced osmotic stress, as evidenced by significantly higher measurements of relative water content (RWC), relative growth rate (RGR), and Callus Growth Rate (CGR). Physiological indices like Relative Water Content (RWC), Relative Growth Rate (RGR), and Callus Growth Rate (CGR) offer valuable insights into a plant's response to environmental stresses like water scarcity. This selection process is crucial for developing more resistant plant varieties that thrive even in challenging environmental conditions.