Mohammad Hedayat

Pyrethrum is an important medicinal perennial herb belonging to the family Asteraceae. A method for rapid micropropagation of pyrethrum through plant regeneration from leaf and petiole explant derived calli has been developed. The petiole and leaf segments were cultured on MS, SH and B5 media supplemented with the combination of auxins and BA for callus induction. All petiole explants on SH medium containing 2 ㎎ㆍL?¹ NAA and 0.2 ㎎ㆍL?¹ BA produced callus. The highest rate of callus growth was observed with the MS medium supplemented with 0.6 ㎎ㆍL?¹ BA and 4 ㎎ㆍL?¹ NAA. Shoot regeneration was obtained successfully by using step-by-step method. Firstly, callus was subcultured on MS medium containing 0.2 ㎎ㆍL?¹ 2,4-D and then, the calli were transferred to MS medium containing 4 ㎎ㆍL?¹ BA, 1 ㎎ㆍL?¹ NAA and 0.5 ㎎ㆍL?¹ folic acid. In the latter step, some protuberances appeared on compact calli. These protuberances produced shoots on MS media containing 1 ㎎ㆍL?¹ BA and 1 ㎎ㆍL?¹ NAA or 1 ㎎ㆍL?¹ BA and 2 ㎎ㆍL?¹ NAA and 0.4 ㎎ㆍL?¹ GA₃. The optimal rooting response was observed on B5 medium supplemented with 2 ㎎ㆍL?¹ NAA, on which 100% of the regenerated shoots developed roots with an average of 16 roots per shoot within 3 weeks. The plantlets were acclimatized and transferred to the greenhouse with 80% survival. This in vitro propagation protocol should be useful for conservation as well as mass propagation of this medicinal plant.