High yields of artemisinin by multi-harvest of Artemisia annua crops

Several field crop experiments were carried out on the annual determinate anti-malarial medicinal plant Artemisia annua over three annual cropping periods in the subtropical agroclimate of Indo-Gangatic plains. The experiments examined the effects of variation in the time of planting and harvest and of number of harvests on the yield of artemisinin and plant growth and development characters related to it. The observations showed that the artemisinin yield was positively correlated with leaf yield and number of harvests. High yields of artemisinin were realized when crop produced artemisinin-rich leaves accompanied by least possible growth of stem tissue, attained by multiple harvesting in early planted full time grown crops. The crops grown for greater than or equal to30 weeks and harvested three and four times gave average yields of 44.1 +/- 14.2 and 74.2 +/- 15.6, respectively, much higher than the maximum yield of 25 kg ha(-1) reported for A. annua in earlier studies. It was concluded that for obtaining artemisinin in high yields the A. annua crop should be ratooned/multi-harvested four times. (C) 2003 Elsevier B.V. All rights reserved.