Benefits of natural biostimulants: Ginger and moringa extracts as seed priming agents to improve salinity tolerance of Ocimum basilicum L.

Using natural biostimulants such as plant extracts is a novel agronomic biofortification strategy to mitigate abiotic stresses such as salinity on crops. This study assessed seed priming effects on physiological and biochemical attributes of basil (Ocimum basilicum L.) under salinity (0 and 100 mM NaCl). Seeds were primed for 12h with distilled water (hydro-priming, H2O), moringa leaf (ME) and ginger rhizome extracts (GE). Salt stress reduced plant fresh weight and hydration, but priming with all agents alleviated salinity impact on basil. ME priming notably boosted fresh weight (+81%) and water content (+50%) compared to unprimed salt-exposed plants. ME-primed plants exhibited the highest proline (2-fold) and sugar (1.5-fold) contents contributing to the osmotic adjustment. Seed priming with ME also reduced malondialdehyde level (MDA) by about 50% enhancing membrane stability. ME also significantly modulated secondary metabolism through the stimulation of polyphenols (+88%), flavonoids (+98%) and total antioxidant activity (+1.4-fold). It upregulated key enzymes: Phenylalanine ammonia-lyase (PAL, +77%), Shikimate dehydrogenase (SKDH, +119%) and Polyphenoloxidase (PPO, +133%). Correlation analysis indicated that priming generally shifted correlation values from negative under salt stress to positive, with most r coefficients ranging between 0.8 and 1.00. Principal Component Analysis (PCA) clearly separated the primed and unprimed conditions, with the first two components explaining over 90% of the variability. Hence, these multivariate approaches confirm the beneficial effect of seed priming on basil growth and metabolism under salinity. Taken together, our findings provide new insights into the potential of using moringa leaf extract as a biostimulant to alleviate environmental stresses.