A survey of artemisinic and dihydroartemisinic acid contents in glasshouse and global field-grown populations of the artemisinin-producing plant Artemisia annua L.

Artemisia annua L is an annual shrub in the Asteraceae that is commercially grown and cropped in Southeast Asia, Africa, Madagascar and India for the antimalarial compound, artemisinin (ART). Demand for a stable supply chain to artemisinin combination therapies has driven forward complementary programs of crop improvement and microbially based semisynthesis to boost global ART production. Recently, photochemical flow-reactor technology has been developed and proposed as an additional input to the supply chain by converting either artemisinic acid (AA) or dihydroartemisinic acid (DHAA) to ART. These compounds are naturally present in A. annua but their content in available commercial lines is unclear. Since 2006 we have undertaken a program to improve A. annua ART yields using diverse germplasm and modern molecular breeding tools. Sesquiterpenoid extracts from eleven diverse populations with low to high ART contents grown under glasshouse conditions had population median AA or DHAA contents never exceeding 0.9% of leaf. dry weight (DW), but ART achieved a maximum median value of 1.5% DW. We also field-trialed 280 distinct lines selected for high ART content including controls, locally grown commercial lines and test hybrids in the major global growing regions over 2010-2011. The trend was for ART to exceed AA or DHAA and content never exceeded 1.6% DW for any compound. These results indicate that currently grown A. annua lines are poor sources of AA and DHAA relative to ART. However, a glasshouse-based forward-screen of over 14,000 individuals from a mutagenized population suggested that increased DHAA yields may be achievable. (C) 2013 Elsevier B.V. All rights reserved.