Overproduction of artemisinin in tetraploid Artemisia annua L.

Tetraploid plants of Artemisia annua L. exhibiting high-artemisinin-yield were successfully induced by treating excised leaves of in vitro plant with 0.1% colchicine. The chromosome number of original diploid plant was confirmed to be 2n=2x=18 whereas that of the tetraploid plant was 2n=4x=36. Morphological and anatomical characteristics of tetraploid plants were obviously different from the diploid counterpart. The tetraploid plants had larger sizes of root system, stomata and glandular secretory trichomes than diploid plant, whereas leaf size in tetraploid was smaller but thicker than diploid. The highest amount of artemisinin content was produced at flower blooming stage in both diploid (2.4% dry weight) and tetraploid (3.8% dry weight) lines. Based on the maximum yield of artemisinin, the optimum harvest time for the diploid lines was flower initiation stage but it was at full blooming stage for tetraploid lines. The highest artemisinin yield in tetraploid plants up to 3.0 mg plant(-1) was detected at this stage which was 1.5 times greater than diploid plants. This is a first report that clearly showed the potential of chromosome doubling strategy to produce high-yield line of A. annua plant for artemisinin production.