Physiological and antioxidant responses of marjoram (Origanum Majorana L.) under drought stress mediated by Salicylic acid and mycorrhizal symbiosis.

Abstract

Drought stress, exacerbated by climate change, is a major limiting factor for herbs cultivation. This study aimed to evaluate the combined effects of salicylic acid (SA) and mycorrhizal fungi (MF) on marjoram under drought stress conditions. The experiment was conducted over two years (2022-2023) using a split factorial design within a randomized complete block with three replications. The study's primary factor was drought stress at three levels: 90% (D0), 70% (D1), and 35% (D2) of field capacity (FC). The secondary factor included two sub-factors: SA concentrations (0, 100, and 300 mg L^-1) and MF inoculation (non-inoculated (M0) and inoculated with Glomus hoi (M1)). Results demonstrated that drought stress decreased relative water content (RWC) (46.8%), chlorophyll content (35%), carotenoids (25.7%), and dry weight (49.3%), while increasing proline (38.6%), soluble sugars (29.4%), electrolyte leakage (44.8%), superoxide dismutase (35.2%), peroxidase (43.1%), and catalase activities (29.3%). Additionally, the combined treatment of SA and MF enhanced water status by 44%, proline content by 12%, and soluble sugar content by 6% under severe drought conditions. Antioxidant enzyme activities (Catalase) were also significantly increased by up to 91% with the combined treatments, supporting the hypothesis that the synergy of SA and MF can effectively mitigate the adverse effects of drought stress on marjoram. Overall, this study demonstrated that the combined application of SA and MF could be a promising strategy for enhancing drought tolerance in marjoram, especially in drought-prone areas. TRIAL REGISTRATION: This study does not involve clinical trials or human participants and, as such, does not require clinical trial registration.