Salt induced modulations in morphological, physiological, and metabolic attributes in in-vitro grown shoots of Withania somnifera (L.) Dunal

Key MessageMicropropagated shoots of Withania somnifera in 2 mg L-1 BAP, responded differentially in different NaCl concentrations with maximum secondary metabolism (withaferin A) at 150 mM NaCl. Due to the increasing dependency of the global population on herbal-based medicines, enhanced production of secondary metabolites has become utmost necessary. Several scientists have revealed the role of NaCl as an abiotic elicitor for in-planta enhancement of phytochemical compounds. Thus, we have micropropagated Withania somnifera from callus tissues in varying concentrations of BAP hormone and found that MS media supplemented with 2 mg L-1 is best suited for maximum yield. Further, the microshoots were treated with varying concentrations (50-250 mM) of NaCl to assess morphological, physico-biochemical, and molecular characteristics. Higher concentrations of NaCl significantly hampered the morphological and photosynthetic attributes of microshoots. A significant enhancement in the proline, phenol, and sugar contents was recorded and the highest accumulation was observed by 139.32%, 53.2%, and 134.94% respectively with 250 mM treated shoots. Free radical scavenging activity and malondialdehydelevel were also up-regulated by 1.44 and 1.75-fold respectively. Similarly, anti-oxidants enzymatic activities were increased linearly. Contrary to this, the highest production of flavonoid (49%) and withaferin-A (97.86%) was limited only upto 150 mM NaCl. Higher accumulation of withanolide was further attested by the Real-time PCR analysis of related genes which revealed their maximum expression by 150 mM salt treatment. Conversely, the expression of photosynthetic-related genes significantly declined after increasing doses of NaCl. These outcomes depicted that a moderate dose of NaCl can act as an elicitor for enhanced secondary metabolites of W. somnifera without compromising its growth significantly.