β-Aminobutyric acid enhances salt tolerance of African marigold by increasing accumulation rate of salicylic acid, γ-Aminobutyric acid and proline

African marigold (Tagetes erecta L.) is one of most cultivated warm-season flowers which is used as cut flower, potted flower or margin flower. Nowadays, one of the most common issues of landscaping is sensitivity of ornamental plants to salinity of soil or irrigation water. In order to investigate the role of β-Aminobutyric acid (BABA) treatments in alleviation of adverse effects of salt stress on African marigold, a factorial experiment was conducted based on completely randomized design with 3 replications during 2022–2023. The experimental treatments included different concentrations of BABA (0, 4, 8 and 12 mM) and different levels of salinity (0, 50, 100 and 150 mM NaCl). Results demonstrated that the negative effects of salinity on marigold characteristics increased by increasing the salinity level, but BABA treatments effectively alleviated the adverse effects. Fresh and dry weight of shoots and root, leaf relative water content, total chlorophyll and carotenoid content, the activity rate of phenylalanine ammonia lyase, catalase and superoxide dismutase, and the accumulation rate of salicylic acid, γ-Aminobutyric acid (GABA) and proline were significantly increased by treatment of marigold plants with BABA 8 mM. Also, this treatment maintained plant phenol and protein content, and reduced H2O2 content, malondialdehyde content and electrolyte leakage under salinity conditions. Accumulation of salicylic acid, GABA and proline caused by BABA treatment could probably be one of most important mechanisms of enhancing salt tolerance rate of marigold plants in this study, therefore, it is recommended to use this treatment as innovative and efficient technique to overcome salinity effects on African marigold plants.