Efficiency of pepper seed invigoration through hydrogen peroxide priming to improve in vitro salt and drought stress tolerance

Priming is considered a potential strategy to counteract the adverse effects of environmental stress factors via the exogenous application of chemicals to improve plant tolerance. In this context, herein, the priming of pepper seeds (Capsicum annuum L. Tunisian var. ‘Baklouti Medenine’) using different concentrations of hydrogen peroxide (H2O2; 1–100 mM) was carried out in in vitro culture subjected to abiotic stress. Seed germination was carried out on Murashige and Skoog (MS) medium, supplemented with stress-inducing agents: sodium chloride (NaCl 85.55 mM) or polyethylene glycol (PEG 6000, 3%) for induction of salt or drought conditions, respectively. The results revealed that depending in priming concentration and medium culture, H2O2 priming enables faster germination for both salt- or drought-stressed seeds, associated with the decline of mean germination time (MGT), time taken for cumulative germination to reach 50% of its maximum (t50) and germination rate (GR), and the increase in germination index (GI). The primed seeds showed great uniformity, reflected by a reduction in time interval between 25% and 75% of viable seeds to germinate (U7525). Under both stress-free and drought stress conditions, priming at 10 mM H2O2 showed a significant decrease of MGT, t50, and GR and an increase in GI. Similarly, the best uniformity (U7525) was obtained at this priming level. Following salinity stress, application of a low concentration of H2O2 (1 mM) reduced t50 and increased GI, versus no significant changes for MGT and GR and a regression in uniformity. No positive effect was noted for H2O2 priming in the final germination percentage and seedling vigor for all cultures. This study suggests that H2O2 priming invigorates pepper seed germination and alleviates the negative effects of salt and drought via the enhancement of seed tolerance.