Callus Induction and Enhancing the Production of Biomass and Pharmaceutical Components of Thymus decussatus as an Endangered Medicinal Plants in Egypt

Thymus decussatus is a perennial herbaceous endangered medicinal plant belongs to family Lamiaceae. However, at the same time they are also threatened due to intensive harvesting. The protocol for inducing callus in Thymus decussatus was created and executed on Murashige and Skoog (MS) medium. This medium was supplemented with various concentrations of 6-Benzylaminopurine (BAP) in combination with Naphthalene acetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D). The callus induction was performed using different types of explants derived from plants growing in vitro. The maximum callus induction percentage of 100%, was achieved by culturing stem segment explants on MS medium supplemented with 1.0 mg-1 BAP and 0.25 mgl-1 2,4-D with callus fresh weight of 16.72 g and a dry weight of 0.37 g. The study investigated the impact of biotic (yeast extract) and abiotic (salicylic acid) elicitation on callus productivity and the accumulation of secondary metabolites. The best concentration of yeast extract (150 μm) that gave the highest callus fresh weight of 10.72 g and the best concentration of salicylic acid (250 μm) that gave the highest callus fresh weight of 15.01 g after 30 days of culturing. Salicylic acid (SA) showed superiority in promoting the development of callus, as evidenced by increased fresh and dry weight. Both elicitors gave positive results in enhancing secondary metabolites accumulation and increased the quantity of some phenolic compounds which have a significant biological effects and benefits for human health.