Exogenous application of salicylic acid and low-dose ionizing radiation increases synthesis of bioactive compounds and upregulates phytosterol production of Bitter melon (Momordica charantia)

Gamma radiation (GR) and salicylic acid (SA) enhance plant traits by regulating growth and development. However, the underlying mechanism of their combined therapies in plants is not well understood. In our study, the potential impact of 100 μM and 500 μM SA and/or 20, 40 Gy in Momordica charantia, a medicinal crop plant was assessed. We observed significant increase in plant root-shoot length and photosynthetic efficiency at 20 Gy dose, which further enhanced under SA application. Overall, simultaneous application of SA and GR also upregulated antioxidant capacity via production of secondary metabolites, such as flavonoids and phenolics. The highest antidiabetic activity with up to 81.5% inhibition of alpha-amylase enzyme was observed at 20 Gy + 500 μM SA combination. The expression of Sterol C-22 Desaturase, a key gene involved in the biosynthesis of β-sitosterol was upregulated under the treatment of GR and/or SA. β-sitosterol is an important compound with potent anti-cholesterol and anti-carcinogenic properties. Our study showed that highest content of β-sitosterol (1082.2 ± 68.2 ng/mg FW) was observed in M. charantia plants exposed to combined 20 Gy + 500 μM SA treatment. Therefore, gamma irradiation and salicylic acid can help in sustainable growth and production of various secondary metabolites in M. charantia, thereby enhancing its agronomic value.