Foliar application of γ-aminobutyric acid (GABA) mitigates drought stress in canola (Brassica napus L.): Insights into antioxidant defense, oxidative stress, lipid profiling, and yield attributes

Water stress is a major environmental challenge that impacts plant growth and performance. Gamma-aminobutyric acid (GABA), an important regulatory molecule in metabolic pathways, plays a key role in plant growth and stress tolerance. This study aimed to examine the effect of foliar GABA treatment on antioxidant enzyme activity, physiological traits, growth measures, and both quantitative and qualitative yield of rapeseed ( Brassica napus L.) under different water stress levels. The experiment was conducted over two consecutive years in a field setting, with three water stress levels (full irrigation, 60%, and 30% of field capacity) and four GABA concentrations (0, 25, 50, and 75 mM). GABA application, especially at 50 and 75 mM, boosted antioxidant enzyme activity and enhanced photosynthetic pigment content, while decreasing levels of proline, malondialdehyde, and hydrogen peroxide. The positive effects of GABA led to increased grain yield, Number of Siliques Per Plant, Number of Seeds Per Silique, and 1000 Kernel Weight. Additionally, GABA treatment raised the percentage, index, and oil yield compared to controls. Water stress reduced linolenic and linoleic fatty acids, while increasing oleic, erucic, and palmitic acids. However, GABA application at 50 and 75 mM alleviated these changes. Overall, the results suggest that GABA application can effectively enhance water stress tolerance and improve rapeseed yield by strengthening the antioxidant system and modulating physiological responses.