Effect of endophytic Bacillus sp. from selected medicinal plants on growth promotion and diosgenin production in Trigonella foenum-graecum

Endophytic microorganisms support the growth of host plants by production of phytohormones, N₂ fixation, synthesis of ACC deaminase, phosphate solubilization and also by means of production of antimicrobial metabolites or siderophores. In the present study, effect of endophytic Bacillus sp. was analysed on the growth enhancement and metabolite modulation in the seedlings of Fenugreek (Trigonella foenum-graecum L.), a well known spice with medicinal properties. Preliminary screening has resulted in the identification of strains CaB 1 (Bacillus cereus), CaB 2 (Bacillus thuringiensis) and CaB 5 (Bacillus sp.) isolated from Capsicum annuum and EcB 4 (Bacillus sp.) isolated from Elettaria cardamomum to have excellent effect on seedling growth enhancement in Fenugreek. The plantlets formed from the treatment were further analysed for leaf number, shoot length, root length, wet weight and diosgenin concentration, which is the principal secondary metabolite of the plant. Interestingly, HPLC analysis has confirmed the ability of CaB 5 to induce highest level of diosgenin biosynthesis (527.83 ± 13.5 μg/mL). The obtained results are of great significance as it widens the exploration of endophytic bacteria on enhanced synthesis of medicinal natural products.