Investigation of Nitrogen and Phosphate Effect on Growth and Rosmarinic Acid Production in Transgenic Mentha aquatica Hairy Root Induction

Mentha aquatica L. as an important medicinal plant is known for its phenolic acids with pharmaceutical properties, especially rosmarinic acid. In order to obtain high amounts of secondary metabolites, the establishment of hairy root cultures through Agrobacterium rhizogenes infection is considered as a suitable alternative. In order to compare the abilities of A.rhizogenes strains to induce hairy roots, the leaf and shoot explants of M.aquatica were used for hairy root induction by five different bacterial strains (ATCC 15834, A13, R318, A4, 9534). Furthermore, the effect of phosphate, nitrogen, and reducing environmental acidity on growth and rosmarinic acid content of hairy roots were studied. The results indicated that the percentage of rooting in stem explants (50%) was higher than the leaves (42.6%). Among the bacterial strains, the strain A4 showed the highest rooting efficiency. It was also demonstrated that phosphate deficiency and increased phosphate levels significantly increased the rosmarinic acid content of hairy roots. Various effects on hairy root biomass were observed in response to different phosphate levels. However, increasing the amount of nitrogen did not affect the studied factors. It was concluded that different types of explants have different potentials of hairy root formation in interaction with bacterial strains.