Salicylic acid and methanol-induced changes in enhancing rapeseed resilience to drought stress conditions

Abstract

Abstract The present study aimed to investigate the effects of foliar applications of salicylic acid at 0 (control), 100, and 200 mg L − 1 and methanol at 0 (control), 10, and 20% (v/v) on morpho-physiological, biochemical, and yield-related attributes of rapeseed ( Brassica napus L.) under drought stress conditions over two consecutive growing seasons. Drought stress was applied at three levels based on cumulative Class A pan evaporation, corresponding to well-watered at 70 mm, moderate drought at 140 mm, and severe drought at 210 mm. The experiment was conducted over two growing seasons using a split-factorial arrangement in a randomized complete block design with three replications. Drought stress significantly reduced grain yield, thousand-seed weight, and photosynthetic pigments, while increasing adaptive responses, such as proline, soluble sugars, and antioxidant enzyme activities. Foliar application of SA and methanol mitigated these negative effects. For instance, 200 mg L − 1 SA increased grain yield by 30.99 and 7.72% compared to control and 100 mg L − 1 SA under moderate drought, whereas 20% methanol enhanced grain yield by 31.62 and 15.93% compared to 10% methanol and control under severe drought stress. Chlorophyll a and relative water content also improved up to 61.99 and 66.28%, respectively, under optimal foliar treatments. Overall, although foliar application of 200 mg L − 1 SA was particularly effective under moderate drought stress, 20% methanol exhibited greater benefits under severe drought stress. The combination of SA and methanol at higher concentrations provided synergistic effects, enhancing physiological, biochemical, and yield-related traits under both irrigation regimes.