Abstract

EFFECT OF DROUGHT STRESS INDUCED BY MANNITOL AND POLYETHYLENE GLYCOL ON GROWTH AND SILYMARIN CONTENT OF MILK THISTLE CALLUS CULTURES

Shawky A. Bekheet*

Abstract

This study was carried out to investigate the effect of drought stress on in vitro growth and silymarin content of Milk thistle. Callus was induced from leaf explants using MS medium supplemented with 5 mg/l NAA + 2 mg/l Kin + 0.1 mg/l GA3. Supplementation of culture medium with mannitol slightly depressed both fresh weight and growth value of callus. However, mannitol caused increasing of dry matter and silymarin content. Addition 40 mg/l of mannitol to culture medium was the best concentration for total silymarin production. Moreover, silybin B was more responsive to osmotic stress induced by mannitol stress compared with the other measured component of silymarin. Otherwise, polyethylene glycol (PEG) caused a progressive reduction in both fresh weight and growth value. However, presence of PEG (15 %) in culture medium strongly enhanced silymarin accumulation as well as dry matter of callus. This treatment increased both silybin A and B (the most important components of silymarin) to a level more seven fold higher than that of the control.

Keywords: Milk thistle, mannitol, polyethylene glycol, callus, silymarin.